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PROC(5)                    Linux Programmer's ManualPROC(5)NAME       proc - process information pseudo-filesystemDESCRIPTION       The  proc filesystem is a pseudo-filesystem which provides an interface       to kernel data structures.  It is commonly  mounted  at  /proc.   Typi-       cally,  it  is  mounted automatically by the system, but it can also be       mounted manually using a command such as:           mount -t proc proc /proc       Most of the files in the proc filesystem are read-only, but some  files       are writable, allowing kernel variables to be changed.   Mount options       The proc filesystem supports the following mount options:       hidepid=n (since Linux 3.3)              This   option   controls  who  can  access  the  information  in              /proc/[pid] directories.  The argument, n, is one of the follow-              ing values:              0   Everybody  may  access all /proc/[pid] directories.  This is                  the traditional behavior, and the default if this mount  op-                  tion is not specified.              1   Users  may  not  access  files and subdirectories inside any                  /proc/[pid] directories but their own (the  /proc/[pid]  di-                  rectories  themselves remain visible).  Sensitive files such                  as /proc/[pid]/cmdline and /proc/[pid]/status are  now  pro-                  tected  against  other  users.   This makes it impossible to                  learn whether any user is running  a  specific  program  (so                  long  as  the program doesn't otherwise reveal itself by its                  behavior).              2   As for mode 1, but in addition the  /proc/[pid]  directories                  belonging  to other users become invisible.  This means that                  /proc/[pid] entries can no longer be used  to  discover  the                  PIDs  on  the  system.   This  doesn't  hide the fact that a                  process with a specific PID value exists (it can be  learned                  by  other  means,  for  example,  by "kill -0 $PID"), but it                  hides a process's UID and  GID,  which  could  otherwise  be                  learned  by  employingstat(2)  on a /proc/[pid] directory.                  This greatly complicates an attacker's task of gathering in-                  formation about running processes (e.g., discovering whether                  some daemon is running with elevated privileges, whether an-                  other  user is running some sensitive program, whether other                  users are running any program at all, and so on).       gid=gid (since Linux 3.3)              Specifies the ID of a group  whose  members  are  authorized  to              learn process information otherwise prohibited by hidepid (i.e.,              users in this group behave as  though  /proc  was  mounted  with              hidepid=0).   This  group  should  be used instead of approaches              such as putting nonroot users into thesudoers(5) file.   Overview       Underneath /proc, there are the following general groups of  files  and       subdirectories:       /proc/[pid] subdirectories              Each  one of these subdirectories contains files and subdirecto-              ries exposing information about the process with the correspond-              ing process ID.              Underneath each of the /proc/[pid] directories, a task subdirec-              tory contains subdirectories of the form task/[tid], which  con-              tain  corresponding information about each of the threads in the              process, where tid is the kernel thread ID of the thread.              The  /proc/[pid]  subdirectories  are  visible  when   iterating              through  /proc  withgetdents(2) (and thus are visible when one              usesls(1) to view the contents of /proc).       /proc/[tid] subdirectories              Each one of these subdirectories contains files and  subdirecto-              ries  exposing information about the thread with the correspond-              ing thread ID.  The contents of these directories are  the  same              as the corresponding /proc/[pid]/task/[tid] directories.              The  /proc/[tid]  subdirectories  are not visible when iterating              through /proc withgetdents(2) (and thus are  not  visible  when              one usesls(1) to view the contents of /proc).       /proc/self              When a process accesses this magic symbolic link, it resolves to              the process's own /proc/[pid] directory.       /proc/thread-self              When a thread accesses this magic symbolic link, it resolves  to              the process's own /proc/self/task/[tid] directory.       /proc/[a-z]*              Various  other  files and subdirectories under /proc expose sys-              tem-wide information.       All of the above are described in more detail below.   Files and directories       The following list provides details of many of the files  and  directo-       ries under the /proc hierarchy.       /proc/[pid]              There  is a numerical subdirectory for each running process; the              subdirectory is named by the process ID.  Each /proc/[pid]  sub-              directory  contains  the  pseudo-files and directories described              below.              The files inside each /proc/[pid] directory are  normally  owned              by  the  effective  user  and effective group ID of the process.              However, as a security measure, the ownership is made  root:root              if  the  process's  "dumpable" attribute is set to a value other              than 1.              Before Linux 4.11, root:root meant the "global" root user ID and              group  ID (i.e., UID 0 and GID 0 in the initial user namespace).              Since Linux 4.11, if the process is in a noninitial  user  name-              space  that has a valid mapping for user (group) ID 0 inside the              namespace, then the user (group) ownership of  the  files  under              /proc/[pid] is instead made the same as the root user (group) ID              of the namespace.  This means that inside  a  container,  things              work as expected for the container "root" user.              The  process's "dumpable" attribute may change for the following              reasons:              *  The  attribute  was   explicitly   set   via   theprctl(2)                 PR_SET_DUMPABLE operation.              *  The   attribute   was   reset   to  the  value  in  the  file                 /proc/sys/fs/suid_dumpable (described below), for the reasons                 described inprctl(2).              Resetting the "dumpable" attribute to 1 reverts the ownership of              the /proc/[pid]/* files to the process's effective UID and GID.       /proc/[pid]/attr              The files in this directory provide an API for security modules.              The  contents  of  this directory are files that can be read and              written in order to set security-related attributes.   This  di-              rectory was added to support SELinux, but the intention was that              the API be general enough to  support  other  security  modules.              For  the  purpose  of  explanation, examples of how SELinux uses              these files are provided below.              This directory is present only if the kernel was configured with              CONFIG_SECURITY.       /proc/[pid]/attr/current (since Linux 2.6.0)              The  contents  of  this  file represent the current security at-              tributes of the process.              In SELinux, this file is used to get the security context  of  a              process.   Prior to Linux 2.6.11, this file could not be used to              set the security context (a  write  was  always  denied),  since              SELinux  limited  process security transitions toexecve(2) (see              the description of /proc/[pid]/attr/exec, below).   Since  Linux              2.6.11,  SELinux  lifted  this  restriction and began supporting              "set" operations via writes to this node if authorized  by  pol-              icy,  although use of this operation is only suitable for appli-              cations that are trusted to maintain any desired separation  be-              tween the old and new security contexts.              Prior  to  Linux  2.6.28, SELinux did not allow threads within a              multi-threaded process to set their security  context  via  this              node  as it would yield an inconsistency among the security con-              texts of the threads sharing the same memory space.  Since Linux              2.6.28,  SELinux  lifted  this  restriction and began supporting              "set" operations for threads within a multithreaded  process  if              the new security context is bounded by the old security context,              where the bounded relation is defined in policy  and  guarantees              that the new security context has a subset of the permissions of              the old security context.              Other security modules may choose to  support  "set"  operations              via writes to this node.       /proc/[pid]/attr/exec (since Linux 2.6.0)              This  file  represents  the  attributes to assign to the process              upon a subsequentexecve(2).              In SELinux, this is needed to support  role/domain  transitions,              andexecve(2)  is  the preferred point to make such transitions              because it offers better control over the initialization of  the              process  in the new security label and the inheritance of state.              In SELinux, this attribute is reset onexecve(2) so that the new              program  reverts to the default behavior for anyexecve(2) calls              that it may make.  In SELinux, a process can set  only  its  own              /proc/[pid]/attr/exec attribute.       /proc/[pid]/attr/fscreate (since Linux 2.6.0)              This  file  represents the attributes to assign to files created              by  subsequent  calls  toopen(2),mkdir(2),symlink(2),  andmknod(2)              SELinux  employs  this file to support creation of a file (using              the aforementioned system calls) in  a  secure  state,  so  that              there  is no risk of inappropriate access being obtained between              the time of creation and the time that attributes are  set.   In              SELinux,  this  attribute is reset onexecve(2), so that the new              program reverts to the default behavior for  any  file  creation              calls  it may make, but the attribute will persist across multi-              ple file creation calls within a program unless it is explicitly              reset.    In   SELinux,   a   process   can  set  only  its  own              /proc/[pid]/attr/fscreate attribute.       /proc/[pid]/attr/keycreate (since Linux 2.6.18)              If a process writes a security context into this file, all  sub-              sequently  created  keys  (add_key(2)) will be labeled with this              context.  For further information, see the  kernel  source  file              Documentation/security/keys/core.rst  (or file Documentation/se-              curity/keys.txt on Linux between 3.0  and  4.13,  or  Documenta-              tion/keys.txt before Linux 3.0).       /proc/[pid]/attr/prev (since Linux 2.6.0)              This  file  contains  the security context of the process before              the  lastexecve(2);   that   is,   the   previous   value   of              /proc/[pid]/attr/current.       /proc/[pid]/attr/socketcreate (since Linux 2.6.18)              If  a process writes a security context into this file, all sub-              sequently created sockets will be labeled with this context.       /proc/[pid]/autogroup (since Linux 2.6.38)              Seesched(7).       /proc/[pid]/auxv (since 2.6.0)              This contains the contents of the  ELF  interpreter  information              passed  to the process at exec time.  The format is one unsigned              long ID plus one unsigned long value for each entry.   The  last              entry contains two zeros.  See alsogetauxval(3).              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_READ_FSCREDS check; seeptrace(2).       /proc/[pid]/cgroup (since Linux 2.6.24)              Seecgroups(7).       /proc/[pid]/clear_refs (since Linux 2.6.22)              This is a  write-only  file,  writable  only  by  owner  of  the              process.              The following values may be written to the file:              1 (since Linux 2.6.22)                     Reset  the  PG_Referenced and ACCESSED/YOUNG bits for all                     the pages associated with the  process.   (Before  kernel                     2.6.32,  writing  any nonzero value to this file had this                     effect.)              2 (since Linux 2.6.32)                     Reset the PG_Referenced and ACCESSED/YOUNG bits  for  all                     anonymous pages associated with the process.              3 (since Linux 2.6.32)                     Reset  the  PG_Referenced and ACCESSED/YOUNG bits for all                     file-mapped pages associated with the process.              Clearing the PG_Referenced and ACCESSED/YOUNG  bits  provides  a              method to measure approximately how much memory a process is us-              ing.  One first inspects the values in the  "Referenced"  fields              for  the  VMAs  shown in /proc/[pid]/smaps to get an idea of the              memory footprint of the process.  One then clears the  PG_Refer-              enced  and ACCESSED/YOUNG bits and, after some measured time in-              terval, once again  inspects  the  values  in  the  "Referenced"              fields  to  get an idea of the change in memory footprint of the              process during the measured interval.  If one is interested only              in  inspecting the selected mapping types, then the value 2 or 3              can be used instead of 1.              Further values can be written to affect different properties:              4 (since Linux 3.11)                     Clear the soft-dirty bit for  all  the  pages  associated                     with  the  process.   This  is  used (in conjunction with                     /proc/[pid]/pagemap) by the check-point restore system to                     discover which pages of a process have been dirtied since                     the file /proc/[pid]/clear_refs was written to.              5 (since Linux 4.0)                     Reset the peak resident set size ("high water  mark")  to                     the process's current resident set size value.              Writing  any  value  to  /proc/[pid]/clear_refs other than those              listed above has no effect.              The /proc/[pid]/clear_refs file is  present  only  if  the  CON-              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.       /proc/[pid]/cmdline              This  read-only  file  holds  the  complete command line for the              process, unless the process is a zombie.  In  the  latter  case,              there is nothing in this file: that is, a read on this file will              return 0 characters.  The command-line arguments appear in  this              file  as a set of strings separated by null bytes ('\0'), with a              further null byte after the last string.       /proc/[pid]/comm (since Linux 2.6.33)              This file exposes the process's comm value--that is, the command              name associated with the process.  Different threads in the same              process  may  have  different  comm   values,   accessible   via              /proc/[pid]/task/[tid]/comm.   A  thread  may  modify  its  comm              value, or that of any of other thread in the same  thread  group              (see  the discussion of CLONE_THREAD inclone(2)), by writing to              the  file  /proc/self/task/[tid]/comm.   Strings   longer   than              TASK_COMM_LEN (16) characters are silently truncated.              This  file  provides  a superset of theprctl(2) PR_SET_NAME and              PR_GET_NAME operations, and is employed bypthread_setname_np(3)              when used to rename threads other than the caller.       /proc/[pid]/coredump_filter (since Linux 2.6.23)              Seecore(5).       /proc/[pid]/cpuset (since Linux 2.6.12)              Seecpuset(7).       /proc/[pid]/cwd              This  is a symbolic link to the current working directory of the              process.  To find out the current working directory  of  process              20, for instance, you can do this:                  $ cd /proc/20/cwd; /bin/pwd              Note  that  the pwd command is often a shell built-in, and might              not work properly.  Inbash(1), you may use pwd -P.              In a multithreaded process, the contents of this  symbolic  link              are  not  available  if  the  main thread has already terminated              (typically by callingpthread_exit(3)).              Permission to dereference or read  (readlink(2))  this  symbolic              link  is  governed  by a ptrace access mode PTRACE_MODE_READ_FS-              CREDS check; seeptrace(2).       /proc/[pid]/environ              This file contains the initial environment that was set when the              currently  executing program was started viaexecve(2).  The en-              tries are separated by null bytes ('\0'), and  there  may  be  a              null  byte  at  the  end.  Thus, to print out the environment of              process 1, you would do:                  $ cat /proc/1/environ | tr '\000' '\n'              If, after anexecve(2), the  process  modifies  its  environment              (e.g.,  by  calling functions such asputenv(3) or modifying theenviron(7) variable directly), this file will not reflect  those              changes.              Furthermore,  a process may change the memory location that this              file refers viaprctl(2) operations such as PR_SET_MM_ENV_START.              Permission to access this file is governed by  a  ptrace  access              mode PTRACE_MODE_READ_FSCREDS check; seeptrace(2).       /proc/[pid]/exe              Under Linux 2.2 and later, this file is a symbolic link contain-              ing the actual pathname of the executed command.  This  symbolic              link  can  be  dereferenced normally; attempting to open it will              open the executable.  You can even type /proc/[pid]/exe  to  run              another copy of the same executable that is being run by process              [pid].  If the pathname has been  unlinked,  the  symbolic  link              will  contain  the  string  '(deleted)' appended to the original              pathname.  In a multithreaded process, the contents of this sym-              bolic link are not available if the main thread has already ter-              minated (typically by callingpthread_exit(3)).              Permission to dereference or read  (readlink(2))  this  symbolic              link  is  governed  by a ptrace access mode PTRACE_MODE_READ_FS-              CREDS check; seeptrace(2).              Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the              binary  which  was  executed, and appears as a symbolic link.  Areadlink(2) call on this file under Linux 2.0 returns  a  string              in the format:                  [device]:inode              For  example, [0301]:1502 would be inode 1502 on device major 03              (IDE, MFM, etc. drives) minor 01 (first partition on  the  first              drive).find(1) with the -inum option can be used to locate the file.       /proc/[pid]/fd/              This  is a subdirectory containing one entry for each file which              the process has open, named by its file descriptor, and which is              a  symbolic link to the actual file.  Thus, 0 is standard input,              1 standard output, 2 standard error, and so on.              For file descriptors for pipes and sockets, the entries will  be              symbolic links whose content is the file type with the inode.  Areadlink(2) call on this file returns a string in the format:                  type:[inode]              For example, socket:[2248868] will be a socket and its inode  is              2248868.   For  sockets, that inode can be used to find more in-              formation in one of the files under /proc/net/.              For file descriptors that have  no  corresponding  inode  (e.g.,              file    descriptors   produced   bybpf(2),epoll_create(2),eventfd(2),inotify_init(2),perf_event_open(2),signalfd(2),timerfd_create(2), anduserfaultfd(2)), the entry will be a sym-              bolic link with contents of the form                  anon_inode:<file-type>              In many cases (but not all),  the  file-type  is  surrounded  by              square brackets.              For  example, an epoll file descriptor will have a symbolic link              whose content is the string anon_inode:[eventpoll].              In a multithreaded process, the contents of this  directory  are              not  available  if the main thread has already terminated (typi-              cally by callingpthread_exit(3)).              Programs that take a filename as a  command-line  argument,  but              don't take input from standard input if no argument is supplied,              and programs that write to a file named as a command-line  argu-              ment, but don't send their output to standard output if no argu-              ment is supplied, can nevertheless be made to use standard input              or standard output by using /proc/[pid]/fd files as command-line              arguments.  For example, assuming that -i is the flag  designat-              ing an input file and -o is the flag designating an output file:                  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...              and you have a working filter.              /proc/self/fd/N  is  approximately the same as /dev/fd/N in some              UNIX and UNIX-like systems.  Most Linux MAKEDEV scripts symboli-              cally link /dev/fd to /proc/self/fd, in fact.              Most systems provide symbolic links /dev/stdin, /dev/stdout, and              /dev/stderr, which respectively link to the files 0, 1, and 2 in              /proc/self/fd.   Thus the example command above could be written              as:                  $ foobar -i /dev/stdin -o /dev/stdout ...              Permission to dereference or  read  (readlink(2))  the  symbolic              links  in  this  directory  is  governed by a ptrace access mode              PTRACE_MODE_READ_FSCREDS check; seeptrace(2).              Note that for file descriptors referring to  inodes  (pipes  and              sockets, see above), those inodes still have permission bits and              ownership information distinct from those of the  /proc/[pid]/fd              entry, and that the owner may differ from the user and group IDs              of the process.  An unprivileged process may lack permissions to              open them, as in this example:                  $ echo test | sudo -u nobody cat                  test                  $ echo test | sudo -u nobody cat /proc/self/fd/0                  cat: /proc/self/fd/0: Permission denied              File  descriptor  0  refers to the pipe created by the shell and              owned by that shell's user, which is not nobody, so cat does not              have  permission  to  create  a new file descriptor to read from              that inode, even though it can still read from its existing file              descriptor 0.       /proc/[pid]/fdinfo/ (since Linux 2.6.22)              This  is a subdirectory containing one entry for each file which              the process has open, named by its file descriptor.   The  files              in this directory are readable only by the owner of the process.              The contents of each file can  be  read  to  obtain  information              about the corresponding file descriptor.  The content depends on              the type of file referred to by the corresponding file  descrip-              tor.              For regular files and directories, we see something like:                  $ cat /proc/12015/fdinfo/4                  pos:    1000                  flags:  01002002                  mnt_id: 21              The fields are as follows:              pos    This is a decimal number showing the file offset.              flags  This  is  an  octal  number that displays the file access                     mode and file status flags (seeopen(2)).  If the  close-                     on-exec file descriptor flag is set, then flags will also                     include the value O_CLOEXEC.                     Before Linux 3.1, this field  incorrectly  displayed  the                     setting  of  O_CLOEXEC  at  the time the file was opened,                     rather than the  current  setting  of  the  close-on-exec                     flag.              mnt_id This  field,  present  since Linux 3.15, is the ID of the                     mount point containing this file.  See the description of                     /proc/[pid]/mountinfo.              For  eventfd  file  descriptors  (seeeventfd(2)), we see (since              Linux 3.8) the following fields:                  pos: 0                  flags:    02                  mnt_id:   10                  eventfd-count:               40              eventfd-count is the current value of the  eventfd  counter,  in              hexadecimal.              For  epoll  file descriptors (seeepoll(7)), we see (since Linux              3.8) the following fields:                  pos: 0                  flags:    02                  mnt_id:   10                  tfd:        9 events:       19 data: 74253d2500000009                  tfd:        7 events:       19 data: 74253d2500000007              Each of the lines beginning tfd describes one of  the  file  de-              scriptors  being  monitored  via  the epoll file descriptor (seeepoll_ctl(2) for some details).  The tfd field is the number  of              the  file descriptor.  The events field is a hexadecimal mask of              the events being monitored for this file descriptor.   The  data              field is the data value associated with this file descriptor.              For  signalfd  file descriptors (seesignalfd(2)), we see (since              Linux 3.8) the following fields:                  pos: 0                  flags:    02                  mnt_id:   10                  sigmask:  0000000000000006              sigmask is the hexadecimal mask of signals that are accepted via              this  signalfd  file descriptor.  (In this example, bits 2 and 3              are set, corresponding to the signals SIGINT  and  SIGQUIT;  seesignal(7).)              For  inotify  file  descriptors  (seeinotify(7)), we see (since              Linux 3.8) the following fields:                  pos: 0                  flags:    00                  mnt_id:   11                  inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73                  inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73              Each of the lines beginning with "inotify" displays  information              about one file or directory that is being monitored.  The fields              in this line are as follows:              wd     A watch descriptor number (in decimal).              ino    The inode number of the target file (in hexadecimal).              sdev   The ID of the device where the target  file  resides  (in                     hexadecimal).              mask   The  mask  of  events being monitored for the target file                     (in hexadecimal).              If the kernel was built with exportfs support, the path  to  the              target  file  is exposed as a file handle, via three hexadecimal              fields: fhandle-bytes, fhandle-type, and f_handle.              For fanotify file descriptors (seefanotify(7)), we  see  (since              Linux 3.8) the following fields:                  pos: 0                  flags:    02                  mnt_id:   11                  fanotify flags:0 event-flags:88002                  fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73              The  fourth  line displays information defined when the fanotify              group was created viafanotify_init(2):              flags  The flags argument given tofanotify_init(2)  (expressed                     in hexadecimal).              event-flags                     The event_f_flags argument given tofanotify_init(2) (ex-                     pressed in hexadecimal).              Each additional line shown  in  the  file  contains  information              about  one  of  the  marks in the fanotify group.  Most of these              fields are as for inotify, except:              mflags The flags associated with the mark (expressed in hexadec-                     imal).              mask   The events mask for this mark (expressed in hexadecimal).              ignored_mask                     The  mask  of  events that are ignored for this mark (ex-                     pressed in hexadecimal).              For details on these fields, seefanotify_mark(2).              For timerfd file descriptors (seetimerfd(2)),  we  see  (since              Linux 3.17) the following fields:                  pos:    0                  flags:  02004002                  mnt_id: 13                  clockid: 0                  ticks: 0                  settime flags: 03                  it_value: (7695568592, 640020877)                  it_interval: (0, 0)              clockid                     This  is the numeric value of the clock ID (corresponding                     to one of the CLOCK_*  constants  defined  via  <time.h>)                     that  is  used to mark the progress of the timer (in this                     example, 0 is CLOCK_REALTIME).              ticks  This is the number of timer  expirations  that  have  oc-                     curred,  (i.e.,  the  value  thatread(2) on it would re-                     turn).              settime flags                     This field lists the flags with  which  the  timerfd  was                     last  armed  (seetimerfd_settime(2)), in octal (in this                     example,  both   TFD_TIMER_ABSTIME   and   TFD_TIMER_CAN-                     CEL_ON_SET are set).              it_value                     This  field  contains  the amount of time until the timer                     will next expire, expressed in seconds  and  nanoseconds.                     This  is always expressed as a relative value, regardless                     of whether the timer was created using the  TFD_TIMER_AB-                     STIME flag.              it_interval                     This field contains the interval of the timer, in seconds                     and nanoseconds.  (The it_value  and  it_interval  fields                     contain  the  values thattimerfd_gettime(2) on this file                     descriptor would return.)       /proc/[pid]/gid_map (since Linux 3.5)              Seeuser_namespaces(7).       /proc/[pid]/io (since kernel 2.6.20)              This file contains I/O statistics for the process, for example:                  # cat /proc/3828/io                  rchar: 323934931                  wchar: 323929600                  syscr: 632687                  syscw: 632675                  read_bytes: 0                  write_bytes: 323932160                  cancelled_write_bytes: 0              The fields are as follows:              rchar: characters read                     The number of bytes which this task has caused to be read                     from storage.  This is simply the sum of bytes which this                     process passed toread(2) and similar system  calls.   It                     includes things such as terminal I/O and is unaffected by                     whether or not actual physical disk I/O was required (the                     read might have been satisfied from pagecache).              wchar: characters written                     The  number of bytes which this task has caused, or shall                     cause to be written to disk.  Similar caveats apply  here                     as with rchar.              syscr: read syscalls                     Attempt  to count the number of read I/O operations--that                     is, system calls such asread(2) andpread(2).              syscw: write syscalls                     Attempt to count the number of write I/O operations--that                     is, system calls such aswrite(2) andpwrite(2).              read_bytes: bytes read                     Attempt  to  count the number of bytes which this process                     really did cause to be fetched from  the  storage  layer.                     This is accurate for block-backed filesystems.              write_bytes: bytes written                     Attempt  to  count the number of bytes which this process                     caused to be sent to the storage layer.              cancelled_write_bytes:                     The big inaccuracy here is truncate.  If a process writes                     1MB  to a file and then deletes the file, it will in fact                     perform no writeout.  But it will have been accounted  as                     having  caused  1MB of write.  In other words: this field                     represents the number of bytes which this process  caused                     to not happen, by truncating pagecache.  A task can cause                     "negative" I/O too.  If this task  truncates  some  dirty                     pagecache, some I/O which another task has been accounted                     for (in its write_bytes) will not be happening.              Note: In the current implementation, things are a  bit  racy  on              32-bit  systems:  if  process A reads process B's /proc/[pid]/io              while process B  is  updating  one  of  these  64-bit  counters,              process A could see an intermediate result.              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_READ_FSCREDS check; seeptrace(2).       /proc/[pid]/limits (since Linux 2.6.24)              This file displays the soft limit, hard limit, and units of mea-              surement  for  each  of the process's resource limits (see getr-limit(2)).  Up to and including Linux 2.6.35, this file is  pro-              tected  to  allow  reading  only by the real UID of the process.              Since Linux 2.6.36, this file is readable by all  users  on  the              system.       /proc/[pid]/map_files/ (since kernel 3.3)              This  subdirectory  contains  entries  corresponding  to memory-              mapped files (seemmap(2)).  Entries are named by memory  region              start  and  end address pair (expressed as hexadecimal numbers),              and are symbolic links to the mapped files themselves.  Here  is              an example, with the output wrapped and reformatted to fit on an              80-column display:                  # ls -l /proc/self/map_files/                  lr--------. 1 root root 64 Apr 16 21:31                              3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so                  ...              Although these entries are present for memory regions that  were              mapped  with  the MAP_FILE flag, the way anonymous shared memory              (regions created with the MAP_ANON | MAP_SHARED flags) is imple-              mented  in Linux means that such regions also appear on this di-              rectory.  Here is an  example  where  the  target  file  is  the              deleted /dev/zero one:                  lrw-------. 1 root root 64 Apr 16 21:33                              7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)              This  directory  appears  only  if the CONFIG_CHECKPOINT_RESTORE              kernel configuration option is enabled.  Privilege  (CAP_SYS_AD-              MIN) is required to view the contents of this directory.       /proc/[pid]/maps              A  file containing the currently mapped memory regions and their              access permissions.  Seemmap(2) for  some  further  information              about memory mappings.              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_READ_FSCREDS check; seeptrace(2).              The format of the file is:    address           perms offset  dev   inode       pathname    00400000-00452000 r-xp 00000000 08:02 173521      /usr/bin/dbus-daemon    00651000-00652000 r--p 00051000 08:02 173521      /usr/bin/dbus-daemon    00652000-00655000 rw-p 00052000 08:02 173521      /usr/bin/dbus-daemon    00e03000-00e24000 rw-p 00000000 00:00 0           [heap]    00e24000-011f7000 rw-p 00000000 00:00 0           [heap]    ...    35b1800000-35b1820000 r-xp 00000000 08:02 135522  /usr/lib64/ld-2.15.so    35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522  /usr/lib64/ld-2.15.so    35b1a20000-35b1a21000 rw-p 00020000 08:02 135522  /usr/lib64/ld-2.15.so    35b1a21000-35b1a22000 rw-p 00000000 00:00 0    35b1c00000-35b1dac000 r-xp 00000000 08:02 135870  /usr/lib64/libc-2.15.so    35b1dac000-35b1fac000 ---p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so    35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so    35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870  /usr/lib64/libc-2.15.so    ...    f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0    [stack:986]    ...    7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0   [stack]    7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0   [vdso]              The address field is the address space in the process  that  the              mapping occupies.  The perms field is a set of permissions:                  r = read                  w = write                  x = execute                  s = shared                  p = private (copy on write)              The  offset  field  is the offset into the file/whatever; dev is              the device (major:minor); inode is the inode on that device.   0              indicates that no inode is associated with the memory region, as              would be the case with BSS (uninitialized data).              The pathname field will usually be the file that is backing  the              mapping.  For ELF files, you can easily coordinate with the off-              set field by looking at the Offset  field  in  the  ELF  program              headers (readelf -l).              There are additional helpful pseudo-paths:                   [stack]                          The  initial  process's  (also  known  as  the  main                          thread's) stack.                   [stack:<tid>] (from Linux 3.4 to 4.4)                          A thread's stack (where the <tid> is a  thread  ID).                          It  corresponds to the /proc/[pid]/task/[tid]/ path.                          This field was removed in Linux 4.5, since providing                          this information for a process with large numbers of                          threads is expensive.                   [vdso] The virtual dynamically linked shared  object.   Seevdso(7).                   [heap] The process's heap.              If  the pathname field is blank, this is an anonymous mapping as              obtained viammap(2).  There is no easy way to  coordinate  this              back  to a process's source, short of running it throughgdb(1),strace(1), or similar.              pathname is shown unescaped except for newline characters, which              are  replaced with an octal escape sequence.  As a result, it is              not possible to determine whether  the  original  pathname  con-              tained  a  newline  character or the literal \e012 character se-              quence.              If the mapping is file-backed and the file has been deleted, the              string " (deleted)" is appended to the pathname.  Note that this              is ambiguous too.              Under Linux 2.0, there is no field giving pathname.       /proc/[pid]/mem              This file can be used to access the pages of a process's  memory              throughopen(2),read(2), andlseek(2).              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_ATTACH_FSCREDS check; seeptrace(2).       /proc/[pid]/mountinfo (since Linux 2.6.26)              This  file  contains  information  about  mount  points  in  the              process's  mount  namespace  (seemount_namespaces(7)).  It sup-              plies various information  (e.g.,  propagation  state,  root  of              mount for bind mounts, identifier for each mount and its parent)              that is missing from the (older)  /proc/[pid]/mounts  file,  and              fixes  various  other problems with that file (e.g., nonextensi-              bility, failure to distinguish per-mount  versus  per-superblock              options).              The file contains lines of the form:36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)              The  numbers  in parentheses are labels for the descriptions be-              low:              (1)  mount ID: a unique ID for the mount (may  be  reused  afterumount(2)).              (2)  parent  ID:  the ID of the parent mount (or of self for the                   root of this mount namespace's mount tree).                   If a new mount is stacked on top  of  a  previous  existing                   mount  (so that it hides the existing mount) at pathname P,                   then the parent of the new mount is the previous  mount  at                   that  location.   Thus,  when  looking  at  all  the mounts                   stacked at a particular location, the top-most mount is the                   one  that  is not the parent of any other mount at the same                   location.  (Note, however, that this top-most mount will be                   accessible  only if the longest path subprefix of P that is                   a mount point is not itself hidden by a stacked mount.)                   If the parent mount point lies outside the  process's  root                   directory  (seechroot(2)), the ID shown here won't have a                   corresponding record in mountinfo whose mount ID (field  1)                   matches this parent mount ID (because mount points that lie                   outside the process's  root  directory  are  not  shown  in                   mountinfo).  As a special case of this point, the process's                   root mount point may have a parent mount (for the initramfs                   filesystem) that lies outside the process's root directory,                   and an entry for  that  mount  point  will  not  appear  in                   mountinfo.              (3)  major:minor: the value of st_dev for files on this filesys-                   tem (seestat(2)).              (4)  root: the pathname of the directory in the filesystem which                   forms the root of this mount.              (5)  mount  point:  the  pathname of the mount point relative to                   the process's root directory.              (6)  mount options: per-mount options (seemount(2)).              (7)  optional  fields:  zero  or  more  fields   of   the   form                   "tag[:value]"; see below.              (8)  separator:  the  end  of the optional fields is marked by a                   single hyphen.              (9)  filesystem  type:  the  filesystem   type   in   the   form                   "type[.subtype]".              (10) mount source: filesystem-specific information or "none".              (11) super options: per-superblock options (seemount(2)).              Currently,  the  possible  optional  fields  are shared, master,              propagate_from, and unbindable.  Seemount_namespaces(7)  for  a              description of these fields.  Parsers should ignore all unrecog-              nized optional fields.              For  more  information  on  mount  propagation  see:  Documenta-              tion/filesystems/sharedsubtree.txt  in  the  Linux kernel source              tree.       /proc/[pid]/mounts (since Linux 2.4.19)              This file lists all the filesystems  currently  mounted  in  the              process's mount namespace (seemount_namespaces(7)).  The format              of this file is documented infstab(5).              Since kernel version 2.6.15, this file is pollable: after  open-              ing  the  file  for  reading,  a  change  in  this file (i.e., a              filesystem mount or unmount) causesselect(2) to mark  the  file              descriptor  as  having an exceptional condition, andpoll(2) andepoll_wait(2) mark the file as having a  priority  event  (POLL-              PRI).  (Before Linux 2.6.30, a change in this file was indicated              by the file descriptor being marked as readable  forselect(2),              and  being  marked  as having an error condition forpoll(2) andepoll_wait(2).)       /proc/[pid]/mountstats (since Linux 2.6.17)              This file exports information (statistics, configuration  infor-              mation)  about the mount points in the process's mount namespace              (seemount_namespaces(7)).  Lines in this file have the form:                  device /dev/sda7 mounted on /home with fstype ext3 [statistics]                  (       1      )            ( 2 )             (3 ) (4)              The fields in each line are:              (1)  The name of the mounted device (or "nodevice" if  there  is                   no corresponding device).              (2)  The mount point within the filesystem tree.              (3)  The filesystem type.              (4)  Optional  statistics  and  configuration information.  Cur-                   rently (as at Linux 2.6.26), only  NFS  filesystems  export                   information via this field.              This file is readable only by the owner of the process.       /proc/[pid]/net (since Linux 2.6.25)              See the description of /proc/net.       /proc/[pid]/ns/ (since Linux 3.0)              This  is  a subdirectory containing one entry for each namespace              that supports being manipulated bysetns(2).  For more  informa-              tion, seenamespaces(7).       /proc/[pid]/numa_maps (since Linux 2.6.14)              Seenuma(7).       /proc/[pid]/oom_adj (since Linux 2.6.11)              This  file  can be used to adjust the score used to select which              process should be killed in an  out-of-memory  (OOM)  situation.              The  kernel  uses  this  value  for a bit-shift operation of the              process's oom_score value: valid values are in the range -16  to              +15,  plus the special value -17, which disables OOM-killing al-              together for this process.  A positive score increases the like-              lihood  of  this process being killed by the OOM-killer; a nega-              tive score decreases the likelihood.              The default value for this file is 0; a new process inherits its              parent's   oom_adj   setting.   A  process  must  be  privileged              (CAP_SYS_RESOURCE) to update this file.              Since Linux 2.6.36, use of this file is deprecated in  favor  of              /proc/[pid]/oom_score_adj.       /proc/[pid]/oom_score (since Linux 2.6.11)              This  file  displays  the current score that the kernel gives to              this process for the purpose of selecting a process for the OOM-              killer.  A higher score means that the process is more likely to              be selected by the OOM-killer.  The basis for this score is  the              amount  of memory used by the process, with increases (+) or de-              creases (-) for factors including:              * whether the process is privileged (-).              Before kernel 2.6.36 the following factors were also used in the              calculation of oom_score:              * whether  the  process  creates a lot of children usingfork(2)                (+);              * whether the process has been running a long time, or has  used                a lot of CPU time (-);              * whether the process has a low nice value (i.e., > 0) (+); and              * whether the process is making direct hardware access (-).              The  oom_score  also  reflects  the  adjustment specified by the              oom_score_adj or oom_adj setting for the process.       /proc/[pid]/oom_score_adj (since Linux 2.6.36)              This file can be used to adjust the badness  heuristic  used  to              select which process gets killed in out-of-memory conditions.              The  badness  heuristic  assigns  a value to each candidate task              ranging from 0 (never kill) to 1000 (always kill)  to  determine              which  process  is targeted.  The units are roughly a proportion              along that range of allowed  memory  the  process  may  allocate              from, based on an estimation of its current memory and swap use.              For example, if a task is using all allowed memory, its  badness              score  will be 1000.  If it is using half of its allowed memory,              its score will be 500.              There is an additional factor included  in  the  badness  score:              root processes are given 3% extra memory over other tasks.              The  amount  of "allowed" memory depends on the context in which              the OOM-killer was called.  If it is due to the memory  assigned              to  the  allocating  task's  cpuset being exhausted, the allowed              memory represents the set of mems assigned to that  cpuset  (seecpuset(7)).   If  it  is  due to a mempolicy's node(s) being ex-              hausted, the allowed memory  represents  the  set  of  mempolicy              nodes.   If  it  is  due to a memory limit (or swap limit) being              reached, the allowed memory is that configured limit.   Finally,              if  it  is due to the entire system being out of memory, the al-              lowed memory represents all allocatable resources.              The value of oom_score_adj is added to the badness score  before              it  is  used to determine which task to kill.  Acceptable values              range    from     -1000     (OOM_SCORE_ADJ_MIN)     to     +1000              (OOM_SCORE_ADJ_MAX).   This  allows  user  space  to control the              preference for OOM-killing, ranging  from  always  preferring  a              certain  task  or completely disabling it from OOM killing.  The              lowest possible value, -1000, is equivalent  to  disabling  OOM-              killing  entirely  for  that task, since it will always report a              badness score of 0.              Consequently, it is very simple for user  space  to  define  the              amount  of  memory  to  consider  for  each  task.   Setting  an              oom_score_adj value of +500, for example, is roughly  equivalent              to  allowing  the  remainder  of  tasks sharing the same system,              cpuset, mempolicy, or memory  controller  resources  to  use  at              least  50%  more  memory.   A  value of -500, on the other hand,              would be roughly equivalent to discounting 50% of the task's al-              lowed memory from being considered as scoring against the task.              For    backward    compatibility    with    previous    kernels,              /proc/[pid]/oom_adj can still be used to tune the badness score.              Its value is scaled linearly with oom_score_adj.              Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will              change the other with its scaled value.              Thechoom(1) program provides a command-line interface  for  ad-              justing  the oom_score_adj value of a running process or a newly              executed command.       /proc/[pid]/pagemap (since Linux 2.6.25)              This file shows the mapping of each  of  the  process's  virtual              pages  into  physical page frames or swap area.  It contains one              64-bit value for each virtual page, with the bits  set  as  fol-              lows:                   63     If set, the page is present in RAM.                   62     If set, the page is in swap space                   61 (since Linux 3.5)                          The page is a file-mapped page or a shared anonymous                          page.                   60-57 (since Linux 3.11)                          Zero                   56 (since Linux 4.2)                          The page is exclusively mapped.                   55 (since Linux 3.11)                          PTE is soft-dirty (see the kernel source file  Docu-                          mentation/admin-guide/mm/soft-dirty.rst).                   54-0   If  the  page is present in RAM (bit 63), then these                          bits provide the page frame  number,  which  can  be                          used to index /proc/kpageflags and /proc/kpagecount.                          If the page is present in swap (bit 62),  then  bits                          4-0  give  the  swap  type, and bits 54-5 encode the                          swap offset.              Before Linux 3.11, bits 60-55 were used to encode the base-2 log              of the page size.              To  employ /proc/[pid]/pagemap efficiently, use /proc/[pid]/maps              to determine which areas of memory are actually mapped and  seek              to skip over unmapped regions.              The  /proc/[pid]/pagemap  file  is  present  only  if  the  CON-              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.              Permission to access this file is governed by  a  ptrace  access              mode PTRACE_MODE_READ_FSCREDS check; seeptrace(2).       /proc/[pid]/personality (since Linux 2.6.28)              This  read-only  file exposes the process's execution domain, as              set bypersonality(2).  The value is  displayed  in  hexadecimal              notation.              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_ATTACH_FSCREDS check; seeptrace(2).       /proc/[pid]/root              UNIX and Linux support the idea of a  per-process  root  of  the              filesystem,  set  by  thechroot(2) system call.  This file is a              symbolic link that points to the process's root  directory,  and              behaves in the same way as exe, and fd/*.              Note  however  that this file is not merely a symbolic link.  It              provides the same view of the filesystem  (including  namespaces              and  the  set  of per-process mounts) as the process itself.  An              example illustrates this point.  In one  terminal,  we  start  a              shell  in  new  user  and mount namespaces, and in that shell we              create some new mount points:                  $ PS1='sh1# ' unshare -Urnm                  sh1# mount -t tmpfs tmpfs /etc  # Mount empty tmpfs at /etc                  sh1# mount --bind /usr /dev     # Mount /usr at /dev                  sh1# echo $$                  27123              In a second terminal window, in the initial mount namespace,  we              look  at the contents of the corresponding mounts in the initial              and new namespaces:                  $ PS1='sh2# ' sudo sh                  sh2# ls /etc | wc -l                  # In initial NS                  309                  sh2# ls /proc/27123/root/etc | wc -l  # /etc in other NS                  0                                     # The empty tmpfs dir                  sh2# ls /dev | wc -l                  # In initial NS                  205                  sh2# ls /proc/27123/root/dev | wc -l  # /dev in other NS                  11                                    # Actually bind                                                        # mounted to /usr                  sh2# ls /usr | wc -l                  # /usr in initial NS                  11              In a multithreaded process, the contents of the /proc/[pid]/root              symbolic  link  are not available if the main thread has already              terminated (typically by callingpthread_exit(3)).              Permission to dereference or read  (readlink(2))  this  symbolic              link  is  governed  by a ptrace access mode PTRACE_MODE_READ_FS-              CREDS check; seeptrace(2).       /proc/[pid]/seccomp (Linux 2.6.12 to 2.6.22)              This file can be used to read and change  the  process's  secure              computing  (seccomp)  mode  setting.  It contains the value 0 if              the process is not in seccomp mode, and 1 if the process  is  in              strict  seccomp  mode  (seeseccomp(2)).  Writing 1 to this file              places the process irreversibly in strict seccomp  mode.   (Fur-              ther attempts to write to the file fail with the EPERM error.)              In  Linux  2.6.23,  this  file  went away, to be replaced by theprctl(2) PR_GET_SECCOMP and PR_SET_SECCOMP operations (and later              byseccomp(2) and the Seccomp field in /proc/[pid]/status).       /proc/[pid]/setgroups (since Linux 3.19)              Seeuser_namespaces(7).       /proc/[pid]/smaps (since Linux 2.6.14)              This  file  shows  memory  consumption for each of the process's              mappings.  (Thepmap(1) command displays similar information, in              a  form that may be easier for parsing.)  For each mapping there              is a series of lines such as the following:                  00400000-0048a000 r-xp 00000000 fd:03 960637       /bin/bash                  Size:                552 kB                  Rss:                 460 kB                  Pss:                 100 kB                  Shared_Clean:        452 kB                  Shared_Dirty:          0 kB                  Private_Clean:         8 kB                  Private_Dirty:         0 kB                  Referenced:          460 kB                  Anonymous:             0 kB                  AnonHugePages:         0 kB                  ShmemHugePages:        0 kB                  ShmemPmdMapped:        0 kB                  Swap:                  0 kB                  KernelPageSize:        4 kB                  MMUPageSize:           4 kB                  KernelPageSize:        4 kB                  MMUPageSize:           4 kB                  Locked:                0 kB                  ProtectionKey:         0                  VmFlags: rd ex mr mw me dw              The first of these lines shows the same information as  is  dis-              played for the mapping in /proc/[pid]/maps.  The following lines              show the size of the mapping, the amount of the mapping that  is              currently  resident  in  RAM ("Rss"), the process's proportional              share of this mapping ("Pss"), the number  of  clean  and  dirty              shared  pages  in the mapping, and the number of clean and dirty              private pages in the mapping.  "Referenced" indicates the amount              of  memory  currently marked as referenced or accessed.  "Anony-              mous" shows the amount of memory that does  not  belong  to  any              file.   "Swap"  shows how much would-be-anonymous memory is also              used, but out on swap.              The "KernelPageSize" line (available since Linux 2.6.29) is  the              page  size  used  by the kernel to back the virtual memory area.              This matches the size used by the MMU in the majority of  cases.              However,  one  counter-example occurs on PPC64 kernels whereby a              kernel using 64kB as a base page size may still  use  4kB  pages              for  the  MMU  on  older processors.  To distinguish the two at-              tributes, the "MMUPageSize" line  (also  available  since  Linux              2.6.29) reports the page size used by the MMU.              The  "Locked"  indicates whether the mapping is locked in memory              or not.              The "ProtectionKey" line (available  since  Linux  4.9,  on  x86              only)  contains the memory protection key (seepkeys(7)) associ-              ated with the virtual memory area.  This entry is  present  only              if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC-              TION_KEYS configuration option.              The "VmFlags" line (available since Linux  3.8)  represents  the              kernel  flags  associated  with the virtual memory area, encoded              using the following two-letter codes:                  rd  - readable                  wr  - writable                  ex  - executable                  sh  - shared                  mr  - may read                  mw  - may write                  me  - may execute                  ms  - may share                  gd  - stack segment grows down                  pf  - pure PFN range                  dw  - disabled write to the mapped file                  lo  - pages are locked in memory                  io  - memory mapped I/O area                  sr  - sequential read advise provided                  rr  - random read advise provided                  dc  - do not copy area on fork                  de  - do not expand area on remapping                  ac  - area is accountable                  nr  - swap space is not reserved for the area                  ht  - area uses huge tlb pages                  nl  - non-linear mapping                  ar  - architecture specific flag                  dd  - do not include area into core dump                  sd  - soft-dirty flag                  mm  - mixed map area                  hg  - huge page advise flag                  nh  - no-huge page advise flag                  mg  - mergeable advise flag              "ProtectionKey" field contains the memory  protection  key  (seepkeys(5)) associated with the virtual memory area.  Present only              if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC-              TION_KEYS configuration option. (since Linux 4.6)              The   /proc/[pid]/smaps   file  is  present  only  if  the  CON-              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.       /proc/[pid]/stack (since Linux 2.6.29)              This file provides a symbolic trace of  the  function  calls  in              this  process's kernel stack.  This file is provided only if the              kernel was built with the  CONFIG_STACKTRACE  configuration  op-              tion.              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_ATTACH_FSCREDS check; seeptrace(2).       /proc/[pid]/stat              Status information about the process.  This is  used  byps(1).              It is defined in the kernel source file fs/proc/array.c.              The  fields,  in order, with their properscanf(3) format speci-              fiers, are listed below.  Whether or not certain of these fields              display  valid  information  is governed by a ptrace access mode              PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT check  (refer  toptrace(2)).  If the check denies access, then the field value is              displayed as 0.  The affected  fields  are  indicated  with  the              marking [PT].              (1) pid  %d                        The process ID.              (2) comm  %s                        The  filename of the executable, in parentheses.  This                        is visible whether or not the  executable  is  swapped                        out.              (3) state  %c                        One  of  the  following characters, indicating process                        state:                        R  Running                        S  Sleeping in an interruptible wait                        D  Waiting in uninterruptible disk sleep                        Z  Zombie                        T  Stopped (on a  signal)  or  (before  Linux  2.6.33)                           trace stopped                        t  Tracing stop (Linux 2.6.33 onward)                        W  Paging (only before Linux 2.6.0)                        X  Dead (from Linux 2.6.0 onward)                        x  Dead (Linux 2.6.33 to 3.13 only)                        K  Wakekill (Linux 2.6.33 to 3.13 only)                        W  Waking (Linux 2.6.33 to 3.13 only)                        P  Parked (Linux 3.9 to 3.13 only)              (4) ppid  %d                        The PID of the parent of this process.              (5) pgrp  %d                        The process group ID of the process.              (6) session  %d                        The session ID of the process.              (7) tty_nr  %d                        The  controlling  terminal of the process.  (The minor                        device number is contained in the combination of  bits                        31  to  20  and  7 to 0; the major device number is in                        bits 15 to 8.)              (8) tpgid  %d                        The ID of the foreground process group of the control-                        ling terminal of the process.              (9) flags  %u                        The  kernel  flags word of the process.  For bit mean-                        ings, see the PF_* defines in the Linux kernel  source                        file  include/linux/sched.h.   Details  depend  on the                        kernel version.                        The format for this field was %lu before Linux 2.6.              (10) minflt  %lu                        The number of minor faults the process has made  which                        have not required loading a memory page from disk.              (11) cminflt  %lu                        The  number of minor faults that the process's waited-                        for children have made.              (12) majflt  %lu                        The number of major faults the process has made  which                        have required loading a memory page from disk.              (13) cmajflt  %lu                        The  number of major faults that the process's waited-                        for children have made.              (14) utime  %lu                        Amount of time that this process has been scheduled in                        user   mode,   measured  in  clock  ticks  (divide  by                        sysconf(_SC_CLK_TCK)).   This  includes  guest   time,                        guest_time  (time spent running a virtual CPU, see be-                        low), so that applications that are not aware  of  the                        guest time field do not lose that time from their cal-                        culations.              (15) stime  %lu                        Amount of time that this process has been scheduled in                        kernel  mode,  measured  in  clock  ticks  (divide  by                        sysconf(_SC_CLK_TCK)).              (16) cutime  %ld                        Amount of time that this process's waited-for children                        have  been  scheduled  in user mode, measured in clock                        ticks (divide  by  sysconf(_SC_CLK_TCK)).   (See  alsotimes(2).)   This  includes  guest  time,  cguest_time                        (time spent running a virtual CPU, see below).              (17) cstime  %ld                        Amount of time that this process's waited-for children                        have  been scheduled in kernel mode, measured in clock                        ticks (divide by sysconf(_SC_CLK_TCK)).              (18) priority  %ld                        (Explanation for Linux 2.6) For  processes  running  a                        real-time   scheduling   policy   (policy  below;  seesched_setscheduler(2)), this is the negated scheduling                        priority, minus one; that is, a number in the range -2                        to -100, corresponding to real-time  priorities  1  to                        99.   For  processes  running  under  a  non-real-time                        scheduling policy, this is the raw nice value (setpri-ority(2))  as  represented  in the kernel.  The kernel                        stores nice values as numbers in the range 0 (high) to                        39 (low), corresponding to the user-visible nice range                        of -20 to 19.                        Before Linux 2.6, this was a scaled value based on the                        scheduler weighting given to this process.              (19) nice  %ld                        The  nice  value  (seesetpriority(2)), a value in the                        range 19 (low priority) to -20 (high priority).              (20) num_threads  %ld                        Number of threads in this process (since  Linux  2.6).                        Before kernel 2.6, this field was hard coded to 0 as a                        placeholder for an earlier removed field.              (21) itrealvalue  %ld                        The time in jiffies before the next SIGALRM is sent to                        the  process  due  to an interval timer.  Since kernel                        2.6.17, this field is no  longer  maintained,  and  is                        hard coded as 0.              (22) starttime  %llu                        The  time  the  process started after system boot.  In                        kernels before Linux 2.6, this value was expressed  in                        jiffies.   Since  Linux 2.6, the value is expressed in                        clock ticks (divide by sysconf(_SC_CLK_TCK)).                        The format for this field was %lu before Linux 2.6.              (23) vsize  %lu                        Virtual memory size in bytes.              (24) rss  %ld                        Resident Set Size: number of pages the process has  in                        real  memory.   This is just the pages which count to-                        ward text, data, or stack space.  This  does  not  in-                        clude  pages  which have not been demand-loaded in, or                        which are swapped out.              (25) rsslim  %lu                        Current soft limit in bytes on the rss of the process;                        see the description of RLIMIT_RSS ingetrlimit(2).              (26) startcode  %lu  [PT]                        The address above which program text can run.              (27) endcode  %lu  [PT]                        The address below which program text can run.              (28) startstack  %lu  [PT]                        The address of the start (i.e., bottom) of the stack.              (29) kstkesp  %lu  [PT]                        The  current value of ESP (stack pointer), as found in                        the kernel stack page for the process.              (30) kstkeip  %lu  [PT]                        The current EIP (instruction pointer).              (31) signal  %lu                        The bitmap of pending signals, displayed as a  decimal                        number.   Obsolete, because it does not provide infor-                        mation on real-time  signals;  use  /proc/[pid]/status                        instead.              (32) blocked  %lu                        The  bitmap of blocked signals, displayed as a decimal                        number.  Obsolete, because it does not provide  infor-                        mation  on  real-time  signals; use /proc/[pid]/status                        instead.              (33) sigignore  %lu                        The bitmap of ignored signals, displayed as a  decimal                        number.   Obsolete, because it does not provide infor-                        mation on real-time  signals;  use  /proc/[pid]/status                        instead.              (34) sigcatch  %lu                        The  bitmap  of caught signals, displayed as a decimal                        number.  Obsolete, because it does not provide  infor-                        mation  on  real-time  signals; use /proc/[pid]/status                        instead.              (35) wchan  %lu  [PT]                        This is the "channel" in which the process is waiting.                        It  is  the  address of a location in the kernel where                        the process is sleeping.  The  corresponding  symbolic                        name can be found in /proc/[pid]/wchan.              (36) nswap  %lu                        Number of pages swapped (not maintained).              (37) cnswap  %lu                        Cumulative nswap for child processes (not maintained).              (38) exit_signal  %d  (since Linux 2.1.22)                        Signal to be sent to parent when we die.              (39) processor  %d  (since Linux 2.2.8)                        CPU number last executed on.              (40) rt_priority  %u  (since Linux 2.5.19)                        Real-time scheduling priority, a number in the range 1                        to 99 for processes scheduled under a  real-time  pol-                        icy,   or   0,   for   non-real-time   processes  (seesched_setscheduler(2)).              (41) policy  %u  (since Linux 2.5.19)                        Scheduling policy (seesched_setscheduler(2)).  Decode                        using the SCHED_* constants in linux/sched.h.                        The format for this field was %lu before Linux 2.6.22.              (42) delayacct_blkio_ticks  %llu  (since Linux 2.6.18)                        Aggregated  block  I/O delays, measured in clock ticks                        (centiseconds).              (43) guest_time  %lu  (since Linux 2.6.24)                        Guest time of the process (time spent running  a  vir-                        tual  CPU  for  a guest operating system), measured in                        clock ticks (divide by sysconf(_SC_CLK_TCK)).              (44) cguest_time  %ld  (since Linux 2.6.24)                        Guest time of  the  process's  children,  measured  in                        clock ticks (divide by sysconf(_SC_CLK_TCK)).              (45) start_data  %lu  (since Linux 3.3)  [PT]                        Address above which program initialized and uninitial-                        ized (BSS) data are placed.              (46) end_data  %lu  (since Linux 3.3)  [PT]                        Address below which program initialized and uninitial-                        ized (BSS) data are placed.              (47) start_brk  %lu  (since Linux 3.3)  [PT]                        Address  above which program heap can be expanded withbrk(2).              (48) arg_start  %lu  (since Linux 3.5)  [PT]                        Address above  which  program  command-line  arguments                        (argv) are placed.              (49) arg_end  %lu  (since Linux 3.5)  [PT]                        Address  below  program  command-line arguments (argv)                        are placed.              (50) env_start  %lu  (since Linux 3.5)  [PT]                        Address above which program environment is placed.              (51) env_end  %lu  (since Linux 3.5)  [PT]                        Address below which program environment is placed.              (52) exit_code  %d  (since Linux 3.5)  [PT]                        The thread's exit status in the form reported by wait-pid(2).       /proc/[pid]/statm              Provides information about memory usage, measured in pages.  The              columns are:                  size       (1) total program size                             (same as VmSize in /proc/[pid]/status)                  resident   (2) resident set size                             (same as VmRSS in /proc/[pid]/status)                  shared     (3) number of resident shared pages (i.e., backed by a file)                             (same as RssFile+RssShmem in /proc/[pid]/status)                  text       (4) text (code)                  lib        (5) library (unused since Linux 2.6; always 0)                  data       (6) data + stack                  dt         (7) dirty pages (unused since Linux 2.6; always 0)       /proc/[pid]/status              Provides  much  of  the  information  in  /proc/[pid]/stat   and              /proc/[pid]/statm in a format that's easier for humans to parse.              Here's an example:                  $ cat /proc/$$/status                  Name:   bash                  Umask:  0022                  State:  S (sleeping)                  Tgid:   17248                  Ngid:   0                  Pid:    17248                  PPid:   17200                  TracerPid:      0                  Uid:    1000    1000    1000    1000                  Gid:    100     100     100     100                  FDSize: 256                  Groups: 16 33 100                  NStgid: 17248                  NSpid:  17248                  NSpgid: 17248                  NSsid:  17200                  VmPeak:     131168 kB                  VmSize:     131168 kB                  VmLck:           0 kB                  VmPin:           0 kB                  VmHWM:       13484 kB                  VmRSS:       13484 kB                  RssAnon:     10264 kB                  RssFile:      3220 kB                  RssShmem:        0 kB                  VmData:      10332 kB                  VmStk:         136 kB                  VmExe:         992 kB                  VmLib:        2104 kB                  VmPTE:          76 kB                  VmPMD:          12 kB                  VmSwap:          0 kB                  HugetlbPages:          0 kB        # 4.4                  CoreDumping:   0                       # 4.15                  Threads:        1                  SigQ:   0/3067                  SigPnd: 0000000000000000                  ShdPnd: 0000000000000000                  SigBlk: 0000000000010000                  SigIgn: 0000000000384004                  SigCgt: 000000004b813efb                  CapInh: 0000000000000000                  CapPrm: 0000000000000000                  CapEff: 0000000000000000                  CapBnd: ffffffffffffffff                  CapAmb:   0000000000000000                  NoNewPrivs:     0                  Seccomp:        0                  Speculation_Store_Bypass:       vulnerable                  Cpus_allowed:   00000001                  Cpus_allowed_list:      0                  Mems_allowed:   1                  Mems_allowed_list:      0                  voluntary_ctxt_switches:        150                  nonvoluntary_ctxt_switches:     545              The fields are as follows:              * Name: Command run by this process.              * Umask: Process umask, expressed in octal with a leading  zero;                seeumask(2).  (Since Linux 4.7.)              * State: Current state of the process.  One of "R (running)", "S                (sleeping)", "D (disk  sleep)",  "T  (stopped)",  "T  (tracing                stop)", "Z (zombie)", or "X (dead)".              * Tgid: Thread group ID (i.e., Process ID).              * Ngid: NUMA group ID (0 if none; since Linux 3.13).              * Pid: Thread ID (seegettid(2)).              * PPid: PID of parent process.              * TracerPid: PID of process tracing this process (0 if not being                traced).              * Uid, Gid: Real, effective,  saved  set,  and  filesystem  UIDs                (GIDs).              * FDSize: Number of file descriptor slots currently allocated.              * Groups: Supplementary group list.              * NStgid:  Thread  group ID (i.e., PID) in each of the PID name-                spaces of which [pid] is a member.  The leftmost  entry  shows                the  value  with  respect  to the PID namespace of the process                that mounted this procfs (or the root namespace if mounted  by                the  kernel), followed by the value in successively nested in-                ner namespaces.  (Since Linux 4.1.)              * NSpid: Thread ID in each of the PID namespaces of which  [pid]                is  a  member.   The fields are ordered as for NStgid.  (Since                Linux 4.1.)              * NSpgid: Process group ID in each  of  the  PID  namespaces  of                which  [pid]  is a member.  The fields are ordered as for NSt-                gid.  (Since Linux 4.1.)              * NSsid: descendant namespace session ID hierarchy Session ID in                each  of  the  PID namespaces of which [pid] is a member.  The                fields are ordered as for NStgid.  (Since Linux 4.1.)              * VmPeak: Peak virtual memory size.              * VmSize: Virtual memory size.              * VmLck: Locked memory size (seemlock(2)).              * VmPin: Pinned memory size (since Linux 3.2).  These are  pages                that can't be moved because something needs to directly access                physical memory.              * VmHWM: Peak resident set size ("high water mark").              * VmRSS: Resident set size.  Note that the value here is the sum                of RssAnon, RssFile, and RssShmem.              * RssAnon:  Size  of  resident  anonymous  memory.  (since Linux                4.5).              * RssFile: Size of resident file mappings.  (since Linux 4.5).              * RssShmem: Size of resident shared memory  (includes  System  V                shared  memory,  mappings  fromtmpfs(5), and shared anonymous                mappings).  (since Linux 4.5).              * VmData, VmStk, VmExe: Size of data, stack, and text segments.              * VmLib: Shared library code size.              * VmPTE: Page table entries size (since Linux 2.6.10).              * VmPMD: Size of second-level page tables (added in  Linux  4.0;                removed in Linux 4.15).              * VmSwap:  Swapped-out  virtual memory size by anonymous private                pages; shmem swap usage is not included (since Linux 2.6.34).              * HugetlbPages: Size of hugetlb  memory  portions  (since  Linux                4.4).              * CoreDumping:  Contains the value 1 if the process is currently                dumping core, and 0 if it is not (since Linux 4.15).  This in-                formation can be used by a monitoring process to avoid killing                a process that is currently dumping core, which  could  result                in a corrupted core dump file.              * Threads: Number of threads in process containing this thread.              * SigQ: This field contains two slash-separated numbers that re-                late to queued signals for the real user ID of  this  process.                The  first  of these is the number of currently queued signals                for this real user ID, and the second is the resource limit on                the  number  of  queued  signals for this process (see the de-                scription of RLIMIT_SIGPENDING ingetrlimit(2)).              * SigPnd, ShdPnd: Mask (expressed  in  hexadecimal)  of  signals                pending for thread and for process as a whole (seepthreads(7)                andsignal(7)).              * SigBlk, SigIgn, SigCgt: Masks (expressed in hexadecimal) indi-                cating  signals  being  blocked, ignored, and caught (see sig-nal(7)).              * CapInh, CapPrm, CapEff: Masks (expressed  in  hexadecimal)  of                capabilities  enabled in inheritable, permitted, and effective                sets (seecapabilities(7)).              * CapBnd: Capability  bounding  set,  expressed  in  hexadecimal                (since Linux 2.6.26, seecapabilities(7)).              * CapAmb:  Ambient  capability  set,  expressed  in  hexadecimal                (since Linux 4.3, seecapabilities(7)).              * NoNewPrivs: Value of the no_new_privs bit (since  Linux  4.10,                seeprctl(2)).              * Seccomp:  Seccomp  mode  of  the process (since Linux 3.8, seeseccomp(2)).  0  means  SECCOMP_MODE_DISABLED;  1  means  SEC-                COMP_MODE_STRICT;  2 means SECCOMP_MODE_FILTER.  This field is                provided only if the kernel was built with the  CONFIG_SECCOMP                kernel configuration option enabled.              * Speculation_Store_Bypass:  Speculation  flaw  mitigation state                (since Linux 4.17, seeprctl(2)).              * Cpus_allowed: Hexadecimal mask of CPUs on which  this  process                may run (since Linux 2.6.24, seecpuset(7)).              * Cpus_allowed_list:  Same  as  previous,  but  in "list format"                (since Linux 2.6.26, seecpuset(7)).              * Mems_allowed: Mask of memory nodes  allowed  to  this  process                (since Linux 2.6.24, seecpuset(7)).              * Mems_allowed_list:  Same  as  previous,  but  in "list format"                (since Linux 2.6.26, seecpuset(7)).              * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of                voluntary   and  involuntary  context  switches  (since  Linux                2.6.23).       /proc/[pid]/syscall (since Linux 2.6.27)              This file exposes the system call number and argument  registers              for  the  system  call  currently being executed by the process,              followed by the values of the stack pointer and program  counter              registers.   The  values  of  all six argument registers are ex-              posed, although most system calls use fewer registers.              If the process is blocked, but not in a system  call,  then  the              file displays -1 in place of the system call number, followed by              just the values of the stack pointer and  program  counter.   If              process  is  not blocked, then the file contains just the string              "running".              This file is present only if the kernel was configured with CON-              FIG_HAVE_ARCH_TRACEHOOK.              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_ATTACH_FSCREDS check; seeptrace(2).       /proc/[pid]/task (since Linux 2.6.0)              This is a directory that  contains  one  subdirectory  for  each              thread in the process.  The name of each subdirectory is the nu-              merical thread ID ([tid]) of the thread (seegettid(2)).              Within each of these subdirectories, there is  a  set  of  files              with the same names and contents as under the /proc/[pid] direc-              tories.  For attributes that are shared by all threads, the con-              tents  for each of the files under the task/[tid] subdirectories              will be the same as in the  corresponding  file  in  the  parent              /proc/[pid]  directory (e.g., in a multithreaded process, all of              the task/[tid]/cwd  files  will  have  the  same  value  as  the              /proc/[pid]/cwd  file  in the parent directory, since all of the              threads in a process share a working directory).  For attributes              that are distinct for each thread, the corresponding files under              task/[tid] may have different values (e.g.,  various  fields  in              each  of  the  task/[tid]/status files may be different for each              thread), or they might not exist in /proc/[pid] at all.              In a multithreaded process, the contents of the /proc/[pid]/task              directory  are not available if the main thread has already ter-              minated (typically by callingpthread_exit(3)).       /proc/[pid]/task/[tid]/children (since Linux 3.5)              A space-separated list of child tasks of this task.  Each  child              task is represented by its TID.              This option is intended for use by the checkpoint-restore (CRIU)              system, and reliably provides a list of children only if all  of              the  child  processes  are  stopped or frozen.  It does not work              properly if children of the target task exit while the  file  is              being  read!  Exiting children may cause non-exiting children to              be omitted from the list.  This makes this interface  even  more              unreliable  than  classic  PID-based approaches if the inspected              task and its children aren't frozen, and most code should proba-              bly not use this interface.              Until  Linux  4.2, the presence of this file was governed by the              CONFIG_CHECKPOINT_RESTORE kernel  configuration  option.   Since              Linux 4.2, it is governed by the CONFIG_PROC_CHILDREN option.       /proc/[pid]/timers (since Linux 3.10)              A  list  of  the  POSIX  timers for this process.  Each timer is              listed with a line that starts with the string "ID:".  For exam-              ple:                  ID: 1                  signal: 60/00007fff86e452a8                  notify: signal/pid.2634                  ClockID: 0                  ID: 0                  signal: 60/00007fff86e452a8                  notify: signal/pid.2634                  ClockID: 1              The lines shown for each timer have the following meanings:              ID     The ID for this timer.  This is not the same as the timer                     ID returned bytimer_create(2); rather, it  is  the  same                     kernel-internal  ID  that is available via the si_timerid                     field of the siginfo_t structure (seesigaction(2)).              signal This is the signal number that this timer uses to deliver                     notifications   followed   by   a  slash,  and  then  the                     sigev_value value supplied to the signal handler.   Valid                     only for timers that notify via a signal.              notify The  part  before  the slash specifies the mechanism that                     this timer uses to deliver notifications, and is  one  of                     "thread", "signal", or "none".  Immediately following the                     slash  is  either  the  string  "tid"  for  timers   with                     SIGEV_THREAD_ID  notification,  or  "pid" for timers that                     notify by other mechanisms.  Following the "." is the PID                     of  the  process  (or the kernel thread ID of the thread)                     that will be delivered a signal if the timer delivers no-                     tifications via a signal.              ClockID                     This  field  identifies the clock that the timer uses for                     measuring time.  For most clocks, this is a  number  that                     matches  one  of the user-space CLOCK_* constants exposed                     via <time.h>.   CLOCK_PROCESS_CPUTIME_ID  timers  display                     with     a     value     of    -6    in    this    field.                     CLOCK_THREAD_CPUTIME_ID timers display with a value of -2                     in this field.              This  file is available only when the kernel was configured with              CONFIG_CHECKPOINT_RESTORE.       /proc/[pid]/timerslack_ns (since Linux 4.6)              This file exposes the process's "current" timer slack value, ex-              pressed  in  nanoseconds.   The  file  is writable, allowing the              process's timer slack value to be changed.  Writing  0  to  this              file  resets  the  "current"  timer slack to the "default" timer              slack  value.   For  further  details,  see  the  discussion  of              PR_SET_TIMERSLACK inprctl(2).              Initially,  permission  to  access  this  file was governed by a              ptrace  access  mode   PTRACE_MODE_ATTACH_FSCREDS   check   (seeptrace(2)).   However, this was subsequently deemed too strict a              requirement (and had the side effect that requiring a process to              have  the  CAP_SYS_PTRACE capability would also allow it to view              and change any process's memory).  Therefore, since  Linux  4.9,              only  the (weaker) CAP_SYS_NICE capability is required to access              this file.       /proc/[pid]/uid_map, /proc/[pid]/gid_map (since Linux 3.5)              Seeuser_namespaces(7).       /proc/[pid]/wchan (since Linux 2.6.0)              The symbolic name corresponding to the location  in  the  kernel              where the process is sleeping.              Permission  to  access  this file is governed by a ptrace access              mode PTRACE_MODE_READ_FSCREDS check; seeptrace(2).       /proc/[tid]              There  is a numerical subdirectory for each running thread  that              is  not a thread group leader (i.e., a thread whose thread ID is              not the same as its process ID); the subdirectory  is  named  by              the  thread ID.  Each one of these subdirectories contains files              and subdirectories exposing information about  the  thread  with              the  thread  ID  tid.  The contents of these directories are the              same as the corresponding /proc/[pid]/task/[tid] directories.              The /proc/[tid] subdirectories are not  visible  when  iterating              through  /proc  withgetdents(2) (and thus are not visible when              one usesls(1) to view the contents  of  /proc).   However,  the              pathnames  of  these directories are visible to (i.e., usable as              arguments in) system calls that operate on pathnames.       /proc/apm              Advanced power management version and battery  information  when              CONFIG_APM is defined at kernel compilation time.       /proc/buddyinfo              This file contains information which is used for diagnosing mem-              ory fragmentation issues.  Each line starts with the identifica-              tion  of  the node and the name of the zone which together iden-              tify a memory region This is  then  followed  by  the  count  of              available  chunks  of  a  certain order in which these zones are              split.  The size in bytes of a certain order  is  given  by  the              formula:                  (2^order) * PAGE_SIZE              The  binary  buddy  allocator  algorithm  inside the kernel will              split one chunk into two chunks of a smaller  order  (thus  with              half  the size) or combine two contiguous chunks into one larger              chunk of a higher order (thus with double the size)  to  satisfy              allocation  requests  and  to counter memory fragmentation.  The              order matches the column number, when starting to count at zero.              For example on an x86-64 system:  Node 0, zone     DMA     1    1    1    0    2    1    1    0    1    1    3  Node 0, zone   DMA32    65   47    4   81   52   28   13   10    5    1  404  Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587              In this example, there is one node containing  three  zones  and              there are 11 different chunk sizes.  If the page size is 4 kilo-              bytes, then the first zone called  DMA  (on  x86  the  first  16              megabyte  of memory) has 1 chunk of 4 kilobytes (order 0) avail-              able and has 3 chunks of 4 megabytes (order 10) available.              If the memory is heavily fragmented, the counters for higher or-              der chunks will be zero and allocation of large contiguous areas              will fail.              Further information about the zones can be found in  /proc/zone-              info.       /proc/bus              Contains subdirectories for installed busses.       /proc/bus/pccard              Subdirectory  for  PCMCIA  devices  when CONFIG_PCMCIA is set at              kernel compilation time.       /proc/bus/pccard/drivers       /proc/bus/pci              Contains various bus subdirectories and pseudo-files  containing              information  about  PCI  busses,  installed  devices, and device              drivers.  Some of these files are not ASCII.       /proc/bus/pci/devices              Information about PCI devices.  They  may  be  accessed  throughlspci(8) andsetpci(8).       /proc/cgroups (since Linux 2.6.24)              Seecgroups(7).       /proc/cmdline              Arguments  passed  to the Linux kernel at boot time.  Often done              via a boot manager such aslilo(8) orgrub(8).       /proc/config.gz (since Linux 2.6)              This file exposes the configuration options that  were  used  to              build  the  currently running kernel, in the same format as they              would be shown in the .config file that resulted when  configur-              ing  the  kernel  (using make xconfig, make config, or similar).              The file contents are compressed;  view  or  search  them  usingzcat(1)  andzgrep(1).  As long as no changes have been made to              the following file, the contents of /proc/config.gz are the same              as those provided by:                  cat /lib/modules/$(uname -r)/build/.config              /proc/config.gz  is  provided  only  if the kernel is configured              with CONFIG_IKCONFIG_PROC.       /proc/crypto              A list of the ciphers provided by the kernel  crypto  API.   For              details,  see  the  kernel Linux Kernel Crypto API documentation              available  under  the   kernel   source   directory   Documenta-              tion/crypto/ (or Documentation/DocBook before 4.10; the documen-              tation can be built using a command such as make htmldocs in the              root directory of the kernel source tree).       /proc/cpuinfo              This  is  a  collection of CPU and system architecture dependent              items, for each supported architecture a  different  list.   Two              common  entries  are  processor  which  gives CPU number and bo-              gomips; a system constant that is calculated during kernel  ini-              tialization.   SMP  machines have information for each CPU.  Thelscpu(1) command gathers its information from this file.       /proc/devices              Text listing of major numbers and device groups.   This  can  be              used by MAKEDEV scripts for consistency with the kernel.       /proc/diskstats (since Linux 2.5.69)              This  file  contains  disk  I/O statistics for each disk device.              See the Linux kernel source file  Documentation/iostats.txt  for              further information.       /proc/dma              This  is a list of the registered ISA DMA (direct memory access)              channels in use.       /proc/driver              Empty subdirectory.       /proc/execdomains              List of the execution domains (ABI personalities).       /proc/fb              Frame buffer information when CONFIG_FB is defined during kernel              compilation.       /proc/filesystems              A  text  listing  of  the filesystems which are supported by the              kernel, namely filesystems which were compiled into  the  kernel              or  whose  kernel  modules  are  currently  loaded.   (See  alsofilesystems(5).)  If a filesystem is marked with  "nodev",  this              means  that  it  does  not  require a block device to be mounted              (e.g., virtual filesystem, network filesystem).              Incidentally, this file may be used bymount(8) when no filesys-              tem  is specified and it didn't manage to determine the filesys-              tem type.  Then filesystems contained in  this  file  are  tried              (excepted those that are marked with "nodev").       /proc/fs              Contains subdirectories that in turn contain files with informa-              tion about (certain) mounted filesystems.       /proc/ide              This directory exists on systems with the IDE  bus.   There  are              directories for each IDE channel and attached device.  Files in-              clude:                  cache              buffer size in KB                  capacity           number of sectors                  driver             driver version                  geometry           physical and logical geometry                  identify           in hexadecimal                  media              media type                  model              manufacturer's model number                  settings           drive settings                  smart_thresholds   in hexadecimal                  smart_values       in hexadecimal              Thehdparm(8) utility provides access to this information  in  a              friendly format.       /proc/interrupts              This  is  used to record the number of interrupts per CPU per IO              device.  Since Linux 2.6.24, for the i386 and  x86-64  architec-              tures,  at  least, this also includes interrupts internal to the              system (that is, not associated with a device as such), such  as              NMI  (nonmaskable  interrupt),  LOC (local timer interrupt), and              for SMP systems, TLB (TLB flush  interrupt),  RES  (rescheduling              interrupt),  CAL  (remote function call interrupt), and possibly              others.  Very easy to read formatting, done in ASCII.       /proc/iomem              I/O memory map in Linux 2.4.       /proc/ioports              This is a list of currently registered Input-Output port regions              that are in use.       /proc/kallsyms (since Linux 2.5.71)              This  holds  the  kernel exported symbol definitions used by the              modules(X) tools to dynamically link and bind loadable  modules.              In  Linux  2.5.47 and earlier, a similar file with slightly dif-              ferent syntax was named ksyms.       /proc/kcore              This file represents the physical memory of the  system  and  is              stored  in the ELF core file format.  With this pseudo-file, and              an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be              used to examine the current state of any kernel data structures.              The  total  length  of  the  file is the size of physical memory              (RAM) plus 4 KiB.       /proc/keys (since Linux 2.6.10)              Seekeyrings(7).       /proc/key-users (since Linux 2.6.10)              Seekeyrings(7).       /proc/kmsg              This file can be used instead of thesyslog(2)  system  call  to              read  kernel messages.  A process must have superuser privileges              to read this file, and only one process should read  this  file.              This  file  should  not  be  read if a syslog process is running              which uses thesyslog(2) system call facility to log kernel mes-              sages.              Information in this file is retrieved with thedmesg(1) program.       /proc/kpagecgroup (since Linux 4.3)              This  file  contains  a 64-bit inode number of the memory cgroup              each page is charged to, indexed by page frame number  (see  the              discussion of /proc/[pid]/pagemap).              The  /proc/kpagecgroup  file is present only if the CONFIG_MEMCG              kernel configuration option is enabled.       /proc/kpagecount (since Linux 2.6.25)              This file contains a 64-bit count of the number  of  times  each              physical page frame is mapped, indexed by page frame number (see              the discussion of /proc/[pid]/pagemap).              The  /proc/kpagecount  file  is  present  only   if   the   CON-              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.       /proc/kpageflags (since Linux 2.6.25)              This  file  contains 64-bit masks corresponding to each physical              page frame; it is indexed by page frame number (see the  discus-              sion of /proc/[pid]/pagemap).  The bits are as follows:                   0 - KPF_LOCKED                   1 - KPF_ERROR                   2 - KPF_REFERENCED                   3 - KPF_UPTODATE                   4 - KPF_DIRTY                   5 - KPF_LRU                   6 - KPF_ACTIVE                   7 - KPF_SLAB                   8 - KPF_WRITEBACK                   9 - KPF_RECLAIM                  10 - KPF_BUDDY                  11 - KPF_MMAP           (since Linux 2.6.31)                  12 - KPF_ANON           (since Linux 2.6.31)                  13 - KPF_SWAPCACHE      (since Linux 2.6.31)                  14 - KPF_SWAPBACKED     (since Linux 2.6.31)                  15 - KPF_COMPOUND_HEAD  (since Linux 2.6.31)                  16 - KPF_COMPOUND_TAIL  (since Linux 2.6.31)                  17 - KPF_HUGE           (since Linux 2.6.31)                  18 - KPF_UNEVICTABLE    (since Linux 2.6.31)                  19 - KPF_HWPOISON       (since Linux 2.6.31)                  20 - KPF_NOPAGE         (since Linux 2.6.31)                  21 - KPF_KSM            (since Linux 2.6.32)                  22 - KPF_THP            (since Linux 3.4)                  23 - KPF_BALLOON        (since Linux 3.18)                  24 - KPF_ZERO_PAGE      (since Linux 4.0)                  25 - KPF_IDLE           (since Linux 4.3)              For  further details on the meanings of these bits, see the ker-              nel source file  Documentation/admin-guide/mm/pagemap.rst.   Be-              fore  kernel  2.6.29, KPF_WRITEBACK, KPF_RECLAIM, KPF_BUDDY, and              KPF_LOCKED did not report correctly.              The  /proc/kpageflags  file  is  present  only   if   the   CON-              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.       /proc/ksyms (Linux 1.1.23-2.5.47)              See /proc/kallsyms.       /proc/loadavg              The  first  three  fields  in this file are load average figures              giving the number of jobs in the run queue (state R) or  waiting              for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They              are the same as the load average numbers given byuptime(1)  and              other  programs.  The fourth field consists of two numbers sepa-              rated by a slash (/).  The first of these is the number of  cur-              rently runnable kernel scheduling entities (processes, threads).              The value after the slash is the number of kernel scheduling en-              tities  that  currently exist on the system.  The fifth field is              the PID of the process that was most  recently  created  on  the              system.       /proc/locks              This  file  shows current file locks (flock(2) andfcntl(2)) and              leases (fcntl(2)).              An example of the content shown in this file is the following:                  1: POSIX  ADVISORY  READ  5433 08:01:7864448 128 128                  2: FLOCK  ADVISORY  WRITE 2001 08:01:7864554 0 EOF                  3: FLOCK  ADVISORY  WRITE 1568 00:2f:32388 0 EOF                  4: POSIX  ADVISORY  WRITE 699 00:16:28457 0 EOF                  5: POSIX  ADVISORY  WRITE 764 00:16:21448 0 0                  6: POSIX  ADVISORY  READ  3548 08:01:7867240 1 1                  7: POSIX  ADVISORY  READ  3548 08:01:7865567 1826 2335                  8: OFDLCK ADVISORY  WRITE -1 08:01:8713209 128 191              The fields shown in each line are as follows:              (1) The ordinal position of the lock in the list.              (2) The lock type.  Values that may appear here include:                  FLOCK  This is a BSD file lock created usingflock(2).                  OFDLCK This is an open file description (OFD)  lock  created                         usingfcntl(2).                  POSIX  This  is  a  POSIX  byte-range lock created using fc-ntl(2).              (3) Among the strings that can appear here are the following:                  ADVISORY                         This is an advisory lock.                  MANDATORY                         This is a mandatory lock.              (4) The type of lock.  Values that can appear here are:                  READ   This is a POSIX or OFD read lock,  or  a  BSD  shared                         lock.                  WRITE  This is a POSIX or OFD write lock, or a BSD exclusive                         lock.              (5) The PID of the process that owns the lock.                  Because OFD locks are not owned by a single  process  (since                  multiple  processes  may have file descriptors that refer to                  the same open file description), the value -1  is  displayed                  in  this  field  for  OFD locks.  (Before kernel 4.14, a bug                  meant that the PID of the process  that  initially  acquired                  the lock was displayed instead of the value -1.)              (6) Three  colon-separated subfields that identify the major and                  minor device ID of  the  device  containing  the  filesystem                  where  the locked file resides, followed by the inode number                  of the locked file.              (7) The byte offset of the first byte  of  the  lock.   For  BSD                  locks, this value is always 0.              (8) The  byte  offset of the last byte of the lock.  EOF in this                  field means that the lock extends to the end  of  the  file.                  For BSD locks, the value shown is always EOF.              Since  Linux 4.9, the list of locks shown in /proc/locks is fil-              tered to show just the locks for the processes in the PID  name-              space (seepid_namespaces(7)) for which the /proc filesystem was              mounted.  (In the initial PID namespace, there is  no  filtering              of the records shown in this file.)              Thelslocks(8)  command  provides  a bit more information about              each lock.       /proc/malloc (only up to and including Linux 2.2)              This file is present only  if  CONFIG_DEBUG_MALLOC  was  defined              during compilation.       /proc/meminfo              This  file  reports statistics about memory usage on the system.              It is used byfree(1) to report the amount of free and used mem-              ory (both physical and swap) on the system as well as the shared              memory and buffers used by the kernel.  Each line  of  the  file              consists  of a parameter name, followed by a colon, the value of              the parameter, and an option unit of measurement  (e.g.,  "kB").              The  list  below  describes  the  parameter names and the format              specifier required to read the field value.  Except as noted be-              low,  all  of  the fields have been present since at least Linux              2.6.0.  Some fields are displayed only if the kernel was config-              ured  with  various options; those dependencies are noted in the              list.              MemTotal %lu                     Total usable RAM (i.e., physical RAM minus a few reserved                     bits and the kernel binary code).              MemFree %lu                     The sum of LowFree+HighFree.              MemAvailable %lu (since Linux 3.14)                     An  estimate of how much memory is available for starting                     new applications, without swapping.              Buffers %lu                     Relatively temporary storage for  raw  disk  blocks  that                     shouldn't get tremendously large (20MB or so).              Cached %lu                     In-memory  cache  for  files read from the disk (the page                     cache).  Doesn't include SwapCached.              SwapCached %lu                     Memory that once was swapped out, is swapped back in  but                     still  also  is in the swap file.  (If memory pressure is                     high, these pages don't need to be swapped out again  be-                     cause  they  are  already  in  the swap file.  This saves                     I/O.)              Active %lu                     Memory that has been used more recently and  usually  not                     reclaimed unless absolutely necessary.              Inactive %lu                     Memory which has been less recently used.  It is more el-                     igible to be reclaimed for other purposes.              Active(anon) %lu (since Linux 2.6.28)                     [To be documented.]              Inactive(anon) %lu (since Linux 2.6.28)                     [To be documented.]              Active(file) %lu (since Linux 2.6.28)                     [To be documented.]              Inactive(file) %lu (since Linux 2.6.28)                     [To be documented.]              Unevictable %lu (since Linux 2.6.28)                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU  was                     required.)  [To be documented.]              Mlocked %lu (since Linux 2.6.28)                     (From  Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was                     required.)  [To be documented.]              HighTotal %lu                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)                     Total  amount  of  highmem.   Highmem is all memory above                     ~860MB of physical memory.  Highmem areas are for use  by                     user-space  programs,  or for the page cache.  The kernel                     must use tricks to access this memory, making  it  slower                     to access than lowmem.              HighFree %lu                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)                     Amount of free highmem.              LowTotal %lu                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)                     Total  amount  of  lowmem.  Lowmem is memory which can be                     used for everything that highmem can be used for, but  it                     is  also  available for the kernel's use for its own data                     structures.  Among many other things, it is where  every-                     thing  from  Slab  is  allocated.  Bad things happen when                     you're out of lowmem.              LowFree %lu                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)                     Amount of free lowmem.              MmapCopy %lu (since Linux 2.6.29)                     (CONFIG_MMU is required.)  [To be documented.]              SwapTotal %lu                     Total amount of swap space available.              SwapFree %lu                     Amount of swap space that is currently unused.              Dirty %lu                     Memory which is waiting to get written back to the disk.              Writeback %lu                     Memory which is actively being written back to the disk.              AnonPages %lu (since Linux 2.6.18)                     Non-file backed pages mapped into user-space page tables.              Mapped %lu                     Files  which have been mapped into memory (withmmap(2)),                     such as libraries.              Shmem %lu (since Linux 2.6.32)                     Amount of memory consumed intmpfs(5) filesystems.              KReclaimable %lu (since Linux 4.20)                     Kernel allocations that the kernel will  attempt  to  re-                     claim  under memory pressure.  Includes SReclaimable (be-                     low), and other direct allocations with a shrinker.              Slab %lu                     In-kernel data structures cache.  (Seeslabinfo(5).)              SReclaimable %lu (since Linux 2.6.19)                     Part of Slab, that might be reclaimed, such as caches.              SUnreclaim %lu (since Linux 2.6.19)                     Part of Slab, that cannot be reclaimed  on  memory  pres-                     sure.              KernelStack %lu (since Linux 2.6.32)                     Amount of memory allocated to kernel stacks.              PageTables %lu (since Linux 2.6.18)                     Amount  of  memory  dedicated to the lowest level of page                     tables.              Quicklists %lu (since Linux 2.6.27)                     (CONFIG_QUICKLIST is required.)  [To be documented.]              NFS_Unstable %lu (since Linux 2.6.18)                     NFS pages sent to the server, but not  yet  committed  to                     stable storage.              Bounce %lu (since Linux 2.6.18)                     Memory used for block device "bounce buffers".              WritebackTmp %lu (since Linux 2.6.26)                     Memory used by FUSE for temporary writeback buffers.              CommitLimit %lu (since Linux 2.6.10)                     This is the total amount of memory currently available to                     be allocated on the system, expressed in kilobytes.  This                     limit  is adhered to only if strict overcommit accounting                     is enabled (mode  2  in  /proc/sys/vm/overcommit_memory).                     The  limit  is  calculated  according  to the formula de-                     scribed under /proc/sys/vm/overcommit_memory.   For  fur-                     ther  details,  see  the  kernel  source  file Documenta-                     tion/vm/overcommit-accounting.rst.              Committed_AS %lu                     The amount of memory presently allocated on  the  system.                     The  committed memory is a sum of all of the memory which                     has been allocated by processes, even if it has not  been                     "used"  by them as of yet.  A process which allocates 1GB                     of memory (usingmalloc(3) or similar), but touches  only                     300MB  of that memory will show up as using only 300MB of                     memory even if it has the address space allocated for the                     entire 1GB.                     This  1GB  is memory which has been "committed" to by the                     VM and can be used at any time by the allocating applica-                     tion.  With strict overcommit enabled on the system (mode                     2 in /proc/sys/vm/overcommit_memory),  allocations  which                     would exceed the CommitLimit will not be permitted.  This                     is useful if one needs to guarantee that  processes  will                     not  fail due to lack of memory once that memory has been                     successfully allocated.              VmallocTotal %lu                     Total size of vmalloc memory area.              VmallocUsed %lu                     Amount of vmalloc area which is used.  Since  Linux  4.4,                     this  field is no longer calculated, and is hard coded as                     0.  See /proc/vmallocinfo.              VmallocChunk %lu                     Largest contiguous block of vmalloc area which  is  free.                     Since  Linux  4.4, this field is no longer calculated and                     is hard coded as 0.  See /proc/vmallocinfo.              HardwareCorrupted %lu (since Linux 2.6.32)                     (CONFIG_MEMORY_FAILURE is required.)  [To be documented.]              LazyFree %lu (since Linux 4.12)                     Shows  the  amount  of  memory   marked   bymadvise(2)                     MADV_FREE.              AnonHugePages %lu (since Linux 2.6.38)                     (CONFIG_TRANSPARENT_HUGEPAGE   is   required.)   Non-file                     backed huge pages mapped into user-space page tables.              ShmemHugePages %lu (since Linux 4.8)                     (CONFIG_TRANSPARENT_HUGEPAGE is required.)   Memory  used                     by shared memory (shmem) andtmpfs(5) allocated with huge                     pages              ShmemPmdMapped %lu (since Linux 4.8)                     (CONFIG_TRANSPARENT_HUGEPAGE is required.)  Shared memory                     mapped into user space with huge pages.              CmaTotal %lu (since Linux 3.1)                     Total  CMA  (Contiguous  Memory  Allocator) pages.  (CON-                     FIG_CMA is required.)              CmaFree %lu (since Linux 3.1)                     Free CMA  (Contiguous  Memory  Allocator)  pages.   (CON-                     FIG_CMA is required.)              HugePages_Total %lu                     (CONFIG_HUGETLB_PAGE  is required.)  The size of the pool                     of huge pages.              HugePages_Free %lu                     (CONFIG_HUGETLB_PAGE is required.)  The  number  of  huge                     pages in the pool that are not yet allocated.              HugePages_Rsvd %lu (since Linux 2.6.17)                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of                     huge pages for which a commitment to  allocate  from  the                     pool  has been made, but no allocation has yet been made.                     These reserved huge pages guarantee that  an  application                     will  be  able  to  allocate a huge page from the pool of                     huge pages at fault time.              HugePages_Surp %lu (since Linux 2.6.24)                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of                     huge   pages   in   the   pool   above   the   value   in                     /proc/sys/vm/nr_hugepages.  The maximum number of surplus                     huge  pages  is  controlled  by  /proc/sys/vm/nr_overcom-                     mit_hugepages.              Hugepagesize %lu                     (CONFIG_HUGETLB_PAGE is  required.)   The  size  of  huge                     pages.              DirectMap4k %lu (since Linux 2.6.27)                     Number  of  bytes of RAM linearly mapped by kernel in 4kB                     pages.  (x86.)              DirectMap4M %lu (since Linux 2.6.27)                     Number of bytes of RAM linearly mapped by kernel  in  4MB                     pages.   (x86  with  CONFIG_X86_64  or CONFIG_X86_PAE en-                     abled.)              DirectMap2M %lu (since Linux 2.6.27)                     Number of bytes of RAM linearly mapped by kernel  in  2MB                     pages.    (x86   with   neither  CONFIG_X86_64  nor  CON-                     FIG_X86_PAE enabled.)              DirectMap1G %lu (since Linux 2.6.27)                     (x86 with CONFIG_X86_64 and CONFIG_X86_DIRECT_GBPAGES en-                     abled.)       /proc/modules              A  text list of the modules that have been loaded by the system.              See alsolsmod(8).       /proc/mounts              Before kernel 2.4.19, this file was a list of all  the  filesys-              tems  currently mounted on the system.  With the introduction of              per-process mount namespaces in Linux  2.4.19  (see  mount_name-spaces(7)),  this file became a link to /proc/self/mounts, which              lists the mount points of the  process's  own  mount  namespace.              The format of this file is documented infstab(5).       /proc/mtrr              Memory  Type  Range Registers.  See the Linux kernel source file              Documentation/x86/mtrr.txt  (or  Documentation/mtrr.txt   before              Linux 2.6.28) for details.       /proc/net              This  directory  contains  various files and subdirectories con-              taining information about the networking layer.  The files  con-              tain  ASCII structures and are, therefore, readable withcat(1).              However, the standardnetstat(8) suite provides much cleaner ac-              cess to these files.              With  the  advent of network namespaces, various information re-              lating to the network stack is  virtualized  (see  network_name-spaces(7)).   Thus,  since Linux 2.6.25, /proc/net is a symbolic              link to the directory /proc/self/net, which  contains  the  same              files and directories as listed below.  However, these files and              directories now expose information for the network namespace  of              which the process is a member.       /proc/net/arp              This  holds  an ASCII readable dump of the kernel ARP table used              for address resolutions.  It will show both dynamically  learned              and preprogrammed ARP entries.  The format is:       IP address     HW type   Flags     HW address          Mask   Device       192.168.0.50   0x1       0x2       00:50:BF:25:68:F3   *      eth0       192.168.0.250  0x1       0xc       00:00:00:00:00:00   *      eth0              Here "IP address" is the IPv4 address of the machine and the "HW              type" is the hardware type of the  address  from  RFC 826.   The              flags are the internal flags of the ARP structure (as defined in              /usr/include/linux/if_arp.h) and the "HW address"  is  the  data              link layer mapping for that IP address if it is known.       /proc/net/dev              The  dev pseudo-file contains network device status information.              This gives the number of received and sent packets,  the  number              of  errors and collisions and other basic statistics.  These are              used by theifconfig(8) program to report  device  status.   The              format is: Inter-|   Receive                                                |  Transmit  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0       /proc/net/dev_mcast              Defined in /usr/src/linux/net/core/dev_mcast.c:                  indx interface_name  dmi_u dmi_g dmi_address                  2    eth0            1     0     01005e000001                  3    eth1            1     0     01005e000001                  4    eth2            1     0     01005e000001       /proc/net/igmp              Internet     Group     Management    Protocol.     Defined    in              /usr/src/linux/net/core/igmp.c.       /proc/net/rarp              This file uses the same format as the arp file and contains  the              current reverse mapping database used to providerarp(8) reverse              address lookup services.  If RARP is  not  configured  into  the              kernel, this file will not be present.       /proc/net/raw              Holds  a  dump of the RAW socket table.  Much of the information              is not of use apart from debugging.  The "sl" value is the  ker-              nel  hash  slot for the socket, the "local_address" is the local              address and protocol number pair.  "St" is the  internal  status              of  the  socket.  The "tx_queue" and "rx_queue" are the outgoing              and incoming data queue in terms of kernel  memory  usage.   The              "tr", "tm->when", and "rexmits" fields are not used by RAW.  The              "uid" field holds the  effective  UID  of  the  creator  of  the              socket.       /proc/net/snmp              This file holds the ASCII data needed for the IP, ICMP, TCP, and              UDP management information bases for an SNMP agent.       /proc/net/tcp              Holds a dump of the TCP socket table.  Much of  the  information              is  not of use apart from debugging.  The "sl" value is the ker-              nel hash slot for the socket, the "local_address" is  the  local              address  and  port number pair.  The "rem_address" is the remote              address and port number pair (if connected).  "St" is the inter-              nal status of the socket.  The "tx_queue" and "rx_queue" are the              outgoing and incoming data queue in terms of kernel  memory  us-              age.   The  "tr", "tm->when", and "rexmits" fields hold internal              information of the kernel socket state and are useful  only  for              debugging.   The "uid" field holds the effective UID of the cre-              ator of the socket.       /proc/net/udp              Holds a dump of the UDP socket table.  Much of  the  information              is  not of use apart from debugging.  The "sl" value is the ker-              nel hash slot for the socket, the "local_address" is  the  local              address  and  port number pair.  The "rem_address" is the remote              address and port number pair (if connected).  "St" is the inter-              nal status of the socket.  The "tx_queue" and "rx_queue" are the              outgoing and incoming data queue in terms of kernel  memory  us-              age.  The "tr", "tm->when", and "rexmits" fields are not used by              UDP.  The "uid" field holds the effective UID of the creator  of              the socket.  The format is: sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0       /proc/net/unix              Lists  the  UNIX  domain  sockets  present within the system and              their status.  The format is: Num RefCount Protocol Flags    Type St Inode Path  0: 00000002 00000000 00000000 0001 03    42  1: 00000001 00000000 00010000 0001 01  1948 /dev/printer              The fields are as follows:              Num:      the kernel table slot number.              RefCount: the number of users of the socket.              Protocol: currently always 0.              Flags:    the internal kernel flags holding the  status  of  the                        socket.              Type:     the  socket  type.   For  SOCK_STREAM sockets, this is                        0001; for SOCK_DGRAM sockets,  it  is  0002;  and  for                        SOCK_SEQPACKET sockets, it is 0005.              St:       the internal state of the socket.              Inode:    the inode number of the socket.              Path:     the bound pathname (if any) of the socket.  Sockets in                        the abstract namespace are included in the  list,  and                        are  shown with a Path that commences with the charac-                        ter '@'.       /proc/net/netfilter/nfnetlink_queue              This file contains information about netfilter user-space queue-              ing,  if  used.  Each line represents a queue.  Queues that have              not been subscribed to by user space are not shown.                     1   4207     0  2 65535     0     0        0  1                    (1)   (2)    (3)(4)  (5)    (6)   (7)      (8)              The fields in each line are:              (1)  The ID of the queue.  This matches what is specified in the                   --queue-num  or  --queue-balance options to theiptables(8)                   NFQUEUE target.  Seeiptables-extensions(8) for more infor-                   mation.              (2)  The netlink port ID subscribed to the queue.              (3)  The  number  of  packets currently queued and waiting to be                   processed by the application.              (4)  The copy mode of the queue.  It is either 1 (metadata only)                   or 2 (also copy payload data to user space).              (5)  Copy  range;  that  is,  how  many  bytes of packet payload                   should be copied to user space at most.              (6)  queue dropped.  Number of packets that had to be dropped by                   the kernel because too many packets are already waiting for                   user space to send back the mandatory accept/drop verdicts.              (7)  queue user dropped.  Number of packets  that  were  dropped                   within  the  netlink  subsystem.  Such drops usually happen                   when the corresponding socket buffer is full; that is, user                   space is not able to read messages fast enough.              (8)  sequence  number.  Every queued packet is associated with a                   (32-bit) monotonically-increasing  sequence  number.   This                   shows the ID of the most recent packet queued.              The last number exists only for compatibility reasons and is al-              ways 1.       /proc/partitions              Contains the major and minor numbers of each partition  as  well              as the number of 1024-byte blocks and the partition name.       /proc/pci              This  is  a  listing of all PCI devices found during kernel ini-              tialization and their configuration.              This file has been deprecated in favor of a new /proc  interface              for  PCI  (/proc/bus/pci).   It  became  optional  in  Linux 2.2              (available with CONFIG_PCI_OLD_PROC set at kernel  compilation).              It  became  once more nonoptionally enabled in Linux 2.4.  Next,              it was deprecated  in  Linux  2.6  (still  available  with  CON-              FIG_PCI_LEGACY_PROC  set),  and finally removed altogether since              Linux 2.6.17.       /proc/profile (since Linux 2.4)              This file is present only if the kernel was booted with the pro-              file=1  command-line option.  It exposes kernel profiling infor-              mation in a binary format for use  byreadprofile(1).   Writing              (e.g.,  an empty string) to this file resets the profiling coun-              ters; on some architectures, writing a binary integer "profiling              multiplier"  of  size  sizeof(int)  sets the profiling interrupt              frequency.       /proc/scsi              A directory with the scsi mid-level pseudo-file and various SCSI              low-level driver directories, which contain a file for each SCSI              host in this system, all of which give the status of  some  part              of  the SCSI IO subsystem.  These files contain ASCII structures              and are, therefore, readable withcat(1).              You can also write to some of the files to reconfigure the  sub-              system or switch certain features on or off.       /proc/scsi/scsi              This  is a listing of all SCSI devices known to the kernel.  The              listing is similar to the one seen  during  bootup.   scsi  cur-              rently  supports only the add-single-device command which allows              root to add a hotplugged device to the list of known devices.              The command                  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi              will cause host scsi1 to scan on SCSI channel 0 for a device  on              ID  5 LUN 0.  If there is already a device known on this address              or the address is invalid, an error will be returned.       /proc/scsi/[drivername]              [drivername]  can  currently  be  NCR53c7xx,  aha152x,  aha1542,              aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,              pas16, qlogic, scsi_debug, seagate, t128,  u15-24f,  ultrastore,              or  wd7000.  These directories show up for all drivers that reg-              istered at least one SCSI HBA.   Every  directory  contains  one              file  per  registered  host.  Every host-file is named after the              number the host was assigned during initialization.              Reading these files will usually show driver and host configura-              tion, statistics, and so on.              Writing  to  these  files  allows  different things on different              hosts.  For example, with the latency  and  nolatency  commands,              root  can  switch on and off command latency measurement code in              the eata_dma driver.  With the lockup and unlock commands,  root              can control bus lockups simulated by the scsi_debug driver.       /proc/self              This  directory  refers  to  the  process  accessing  the  /proc              filesystem, and is identical to the /proc directory named by the              process ID of the same process.       /proc/slabinfo              Information about kernel caches.  Seeslabinfo(5) for details.       /proc/stat              kernel/system statistics.  Varies with architecture.  Common en-              tries include:              cpu 10132153 290696 3084719 46828483 16683 0 25195 0 175628 0              cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0                     The  amount  of  time,  measured  in  units  of   USER_HZ                     (1/100ths   of   a  second  on  most  architectures,  use                     sysconf(_SC_CLK_TCK) to obtain the right value), that the                     system  ("cpu"  line)  or  the specific CPU ("cpuN" line)                     spent in various states:                     user   (1) Time spent in user mode.                     nice   (2) Time spent in  user  mode  with  low  priority                            (nice).                     system (3) Time spent in system mode.                     idle   (4)  Time  spent  in  the  idle  task.  This value                            should be USER_HZ times the second  entry  in  the                            /proc/uptime pseudo-file.                     iowait (since Linux 2.5.41)                            (5)  Time waiting for I/O to complete.  This value                            is not reliable, for the following reasons:                            1. The CPU will not  wait  for  I/O  to  complete;                               iowait  is  the time that a task is waiting for                               I/O to complete.  When a  CPU  goes  into  idle                               state  for  outstanding  task I/O, another task                               will be scheduled on this CPU.                            2. On a multi-core CPU, the task waiting  for  I/O                               to  complete  is not running on any CPU, so the                               iowait of each CPU is difficult to calculate.                            3. The value in this field may decrease in certain                               conditions.                     irq (since Linux 2.6.0)                            (6) Time servicing interrupts.                     softirq (since Linux 2.6.0                            (7) Time servicing softirqs.                     steal (since Linux 2.6.11)                            (8)  Stolen time, which is the time spent in other                            operating systems when running  in  a  virtualized                            environment                     guest (since Linux 2.6.24)                            (9) Time spent running a virtual CPU for guest op-                            erating systems under the  control  of  the  Linux                            kernel.                     guest_nice (since Linux 2.6.33)                            (10) Time spent running a niced guest (virtual CPU                            for guest operating systems under the  control  of                            the Linux kernel).              page 5741 1808                     The  number  of  pages the system paged in and the number                     that were paged out (from disk).              swap 1 0                     The number of swap pages that have been  brought  in  and                     out.              intr 1462898                     This  line shows counts of interrupts serviced since boot                     time, for each of the possible  system  interrupts.   The                     first  column is the total of all interrupts serviced in-                     cluding unnumbered architecture specific interrupts; each                     subsequent  column  is the total for that particular num-                     bered interrupt.  Unnumbered interrupts  are  not  shown,                     only summed into the total.              disk_io: (2,0):(31,30,5764,1,2) (3,0):...                     (major,disk_idx):(noinfo,     read_io_ops,     blks_read,                     write_io_ops, blks_written)                     (Linux 2.4 only)              ctxt 115315                     The number of context switches that the system underwent.              btime 769041601                     boot  time,  in  seconds  since  the  Epoch,   1970-01-01                     00:00:00 +0000 (UTC).              processes 86031                     Number of forks since boot.              procs_running 6                     Number of processes in runnable state.  (Linux 2.5.45 on-                     ward.)              procs_blocked 2                     Number of processes blocked waiting for I/O to  complete.                     (Linux 2.5.45 onward.)              softirq  229245889 94 60001584 13619 5175704 2471304 28 51212741              59130143 0 51240672                     This line shows the number of softirq for all CPUs.   The                     first column is the total of all softirqs and each subse-                     quent column is the total for particular softirq.  (Linux                     2.6.31 onward.)       /proc/swaps              Swap areas in use.  See alsoswapon(8).       /proc/sys              This directory (present since 1.3.57) contains a number of files              and subdirectories corresponding  to  kernel  variables.   These              variables  can  be  read  and sometimes modified using the /proc              filesystem, and the (deprecated)sysctl(2) system call.              String values may be terminated by either '\0' or '\n'.              Integer and long values may be written either in decimal  or  in              hexadecimal notation (e.g. 0x3FFF).  When writing multiple inte-              ger or long values, these may be separated by any of the follow-              ing whitespace characters: ' ', '\t', or '\n'.  Using other sep-              arators leads to the error EINVAL.       /proc/sys/abi (since Linux 2.4.10)              This directory may contain files with application binary  infor-              mation.    See   the   Linux   kernel   source  file  Documenta-              tion/sysctl/abi.txt for more information.       /proc/sys/debug              This directory may be empty.       /proc/sys/dev              This  directory  contains  device-specific  information   (e.g.,              dev/cdrom/info).  On some systems, it may be empty.       /proc/sys/fs              This  directory contains the files and subdirectories for kernel              variables related to filesystems.       /proc/sys/fs/binfmt_misc              Documentation for files in this directory can be  found  in  the              Linux   kernel   source   in   the   file   Documentation/admin-              guide/binfmt-misc.rst (or  in  Documentation/binfmt_misc.txt  on              older kernels).       /proc/sys/fs/dentry-state (since Linux 2.2)              This file contains information about the status of the directory              cache (dcache).   The  file  contains  six  numbers,  nr_dentry,              nr_unused,  age_limit  (age  in  seconds), want_pages (pages re-              quested by system) and two dummy values.              * nr_dentry is the number  of  allocated  dentries  (dcache  en-                tries).  This field is unused in Linux 2.2.              * nr_unused is the number of unused dentries.              * age_limit is the age in seconds after which dcache entries can                be reclaimed when memory is short.              * want_pages   is   nonzero   when   the   kernel   has   called                shrink_dcache_pages() and the dcache isn't pruned yet.       /proc/sys/fs/dir-notify-enable              This file can be used to disable or enable the dnotify interface              described infcntl(2) on a system-wide basis.  A value of  0  in              this file disables the interface, and a value of 1 enables it.       /proc/sys/fs/dquot-max              This file shows the maximum number of cached disk quota entries.              On some (2.4) systems, it is not present.  If the number of free              cached  disk quota entries is very low and you have some awesome              number of simultaneous system users, you might want to raise the              limit.       /proc/sys/fs/dquot-nr              This  file  shows the number of allocated disk quota entries and              the number of free disk quota entries.       /proc/sys/fs/epoll (since Linux 2.6.28)              This directory contains the file max_user_watches, which can  be              used  to limit the amount of kernel memory consumed by the epoll              interface.  For further details, seeepoll(7).       /proc/sys/fs/file-max              This file defines a system-wide limit  on  the  number  of  open              files for all processes.  System calls that fail when encounter-              ing this limit fail with the  error  ENFILE.   (See  also  setr-limit(2),  which can be used by a process to set the per-process              limit, RLIMIT_NOFILE, on the number of files it may  open.)   If              you  get  lots of error messages in the kernel log about running              out of file handles (look  for  "VFS:  file-max  limit  <number>              reached"), try increasing this value:                  echo 100000 > /proc/sys/fs/file-max              Privileged  processes  (CAP_SYS_ADMIN) can override the file-max              limit.       /proc/sys/fs/file-nr              This (read-only) file contains three numbers: the number of  al-              located  file  handles  (i.e.,  the  number  of  files presently              opened); the number of free file handles; and the maximum number              of file handles (i.e., the same value as /proc/sys/fs/file-max).              If the number of allocated file handles is close to the maximum,              you  should  consider increasing the maximum.  Before Linux 2.6,              the kernel allocated file handles  dynamically,  but  it  didn't              free  them  again.  Instead the free file handles were kept in a              list for reallocation; the "free file handles"  value  indicates              the  size of that list.  A large number of free file handles in-              dicates that there was a past peak in the  usage  of  open  file              handles.  Since Linux 2.6, the kernel does deallocate freed file              handles, and the "free file handles" value is always zero.       /proc/sys/fs/inode-max (only present until Linux 2.2)              This file contains the maximum number of in-memory inodes.  This              value  should  be  3-4  times larger than the value in file-max,              since stdin, stdout and network sockets also need  an  inode  to              handle  them.  When you regularly run out of inodes, you need to              increase this value.              Starting with Linux 2.4, there is no longer a  static  limit  on              the number of inodes, and this file is removed.       /proc/sys/fs/inode-nr              This file contains the first two values from inode-state.       /proc/sys/fs/inode-state              This  file  contains  seven  numbers: nr_inodes, nr_free_inodes,              preshrink, and four dummy values (always zero).              nr_inodes is the number of  inodes  the  system  has  allocated.              nr_free_inodes represents the number of free inodes.              preshrink is nonzero when the nr_inodes > inode-max and the sys-              tem needs to prune the inode list instead  of  allocating  more;              since Linux 2.4, this field is a dummy value (always zero).       /proc/sys/fs/inotify (since Linux 2.6.13)              This  directory  contains  files max_queued_events, max_user_in-              stances, and max_user_watches, that can be  used  to  limit  the              amount  of kernel memory consumed by the inotify interface.  For              further details, seeinotify(7).       /proc/sys/fs/lease-break-time              This file specifies the grace period that the kernel grants to a              process holding a file lease (fcntl(2)) after it has sent a sig-              nal to that process notifying it that another process is waiting              to  open the file.  If the lease holder does not remove or down-              grade the lease within this grace period,  the  kernel  forcibly              breaks the lease.       /proc/sys/fs/leases-enable              This  file  can  be  used  to enable or disable file leases (fc-ntl(2)) on a system-wide basis.  If this file contains the value              0, leases are disabled.  A nonzero value enables leases.       /proc/sys/fs/mount-max (since Linux 4.9)              The  value  in  this file specifies the maximum number of mounts              that may exist in a mount namespace.  The default value in  this              file is 100,000.       /proc/sys/fs/mqueue (since Linux 2.6.6)              This   directory   contains   files  msg_max,  msgsize_max,  and              queues_max, controlling the  resources  used  by  POSIX  message              queues.  Seemq_overview(7) for details.       /proc/sys/fs/nr_open (since Linux 2.6.25)              This   file   imposes   ceiling   on  the  value  to  which  the              RLIMIT_NOFILE resource limit can be raised  (seegetrlimit(2)).              This  ceiling  is  enforced for both unprivileged and privileged              process.  The default value in this file  is  1048576.   (Before              Linux  2.6.25,  the  ceiling for RLIMIT_NOFILE was hard-coded to              the same value.)       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid              These files allow you to change the value of the fixed  UID  and              GID.   The  default  is  65534.   Some  filesystems support only              16-bit UIDs and GIDs, although in Linux UIDs  and  GIDs  are  32              bits.   When one of these filesystems is mounted with writes en-              abled, any UID or GID that would exceed 65535 is  translated  to              the overflow value before being written to disk.       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)              Seepipe(7).       /proc/sys/fs/pipe-user-pages-hard (since Linux 4.5)              Seepipe(7).       /proc/sys/fs/pipe-user-pages-soft (since Linux 4.5)              Seepipe(7).       /proc/sys/fs/protected_hardlinks (since Linux 3.6)              When  the value in this file is 0, no restrictions are placed on              the creation of hard links (i.e., this is the historical  behav-              ior before Linux 3.6).  When the value in this file is 1, a hard              link can be created to a target file only if one of the  follow-              ing conditions is true:              *  The calling process has the CAP_FOWNER capability in its user                 namespace and the file UID has a mapping in the namespace.              *  The filesystem UID of the process creating the  link  matches                 the  owner  (UID) of the target file (as described in creden-tials(7), a process's filesystem UID is normally the same  as                 its effective UID).              *  All of the following conditions are true:                  o  the target is a regular file;                  o  the  target  file  does not have its set-user-ID mode bit                     enabled;                  o  the target file does not have both its  set-group-ID  and                     group-executable mode bits enabled; and                  o  the  caller  has  permission to read and write the target                     file (either via the file's permissions mask  or  because                     it has suitable capabilities).              The  default  value  in  this file is 0.  Setting the value to 1              prevents a longstanding class of security issues caused by hard-              link-based  time-of-check, time-of-use races, most commonly seen              in world-writable directories such as /tmp.  The  common  method              of  exploiting  this  flaw is to cross privilege boundaries when              following a given hard link (i.e., a root process follows a hard              link created by another user).  Additionally, on systems without              separated partitions, this stops unauthorized users  from  "pin-              ning"  vulnerable set-user-ID and set-group-ID files against be-              ing upgraded by the administrator, or linking to special files.       /proc/sys/fs/protected_symlinks (since Linux 3.6)              When the value in this file is 0, no restrictions are placed  on              following  symbolic links (i.e., this is the historical behavior              before Linux 3.6).  When the value in this file is  1,  symbolic              links are followed only in the following circumstances:              *  the  filesystem UID of the process following the link matches                 the owner (UID) of the symbolic link (as described in creden-tials(7),  a process's filesystem UID is normally the same as                 its effective UID);              *  the link is not in a sticky world-writable directory; or              *  the symbolic link and its  parent  directory  have  the  same                 owner (UID)              A  system  call  that fails to follow a symbolic link because of              the above restrictions returns the error EACCES in errno.              The default value in this file is 0.  Setting  the  value  to  1              avoids a longstanding class of security issues based on time-of-              check, time-of-use races when accessing symbolic links.       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)              The value in this file is assigned  to  a  process's  "dumpable"              flag in the circumstances described inprctl(2).  In effect, the              value in this file determines whether core dump files  are  pro-              duced  for  set-user-ID or otherwise protected/tainted binaries.              The "dumpable" setting also affects the ownership of files in  a              process's /proc/[pid] directory, as described above.              Three different integer values can be specified:              0 (default)                     This  provides  the traditional (pre-Linux 2.6.13) behav-                     ior.  A core dump will not  be  produced  for  a  process                     which  has  changed  credentials  (by callingseteuid(2),setgid(2), or similar, or by executing a  set-user-ID  or                     set-group-ID  program) or whose binary does not have read                     permission enabled.              1 ("debug")                     All processes dump core when possible.   (Reasons  why  a                     process might nevertheless not dump core are described incore(5).)  The core dump is owned by the filesystem  user                     ID  of  the  dumping  process and no security is applied.                     This is intended for system  debugging  situations  only:                     this  mode  is  insecure  because  it allows unprivileged                     users to examine the memory contents of  privileged  pro-                     cesses.              2 ("suidsafe")                     Any  binary  which  normally would not be dumped (see "0"                     above) is dumped readable by root only.  This allows  the                     user  to  remove  the  core dump file but not to read it.                     For security reasons core dumps in  this  mode  will  not                     overwrite  one  another or other files.  This mode is ap-                     propriate when administrators  are  attempting  to  debug                     problems in a normal environment.                     Additionally, since Linux 3.6, /proc/sys/kernel/core_pat-                     tern must either be an absolute pathname or a  pipe  com-                     mand,  as  detailed incore(5).  Warnings will be written                     to the kernel log if core_pattern does not  follow  these                     rules, and no core dump will be produced.              For  details  of the effect of a process's "dumpable" setting on              ptrace access mode checking, seeptrace(2).       /proc/sys/fs/super-max              This file controls the maximum number of superblocks,  and  thus              the  maximum  number of mounted filesystems the kernel can have.              You need increase only super-max  if  you  need  to  mount  more              filesystems than the current value in super-max allows you to.       /proc/sys/fs/super-nr              This file contains the number of filesystems currently mounted.       /proc/sys/kernel              This  directory contains files controlling a range of kernel pa-              rameters, as described below.       /proc/sys/kernel/acct              This file contains three numbers: highwater, lowwater, and  fre-              quency.   If BSD-style process accounting is enabled, these val-              ues control its behavior.  If free space on filesystem where the              log  lives goes below lowwater percent, accounting suspends.  If              free space gets above  highwater  percent,  accounting  resumes.              frequency  determines  how often the kernel checks the amount of              free space (value is in seconds).  Default values are 4,  2  and              30.   That  is,  suspend accounting if 2% or less space is free;              resume it if 4% or more  space  is  free;  consider  information              about amount of free space valid for 30 seconds.       /proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)              From  Linux 2.6.27 to 3.18, this file was used to control recom-              puting of the value in /proc/sys/kernel/msgmni upon the addition              or  removal  of  memory  or upon IPC namespace creation/removal.              Echoing "1" into this file enabled msgmni automatic  recomputing              (and  triggered  a  recomputation of msgmni based on the current              amount of available memory and number of IPC namespaces).  Echo-              ing  "0" disabled automatic recomputing.  (Automatic recomputing              was  also  disabled  if  a  value  was  explicitly  assigned  to              /proc/sys/kernel/msgmni.)   The default value in auto_msgmni was              1.              Since Linux 3.19, the content of this file has  no  effect  (be-              cause  msgmni  defaults to near the maximum value possible), and              reads from this file always return the value "0".       /proc/sys/kernel/cap_last_cap (since Linux 3.2)              Seecapabilities(7).       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)              This file holds the value of the kernel capability bounding  set              (expressed  as  a  signed  decimal  number).   This set is ANDed              against the capabilities  permitted  to  a  process  during  ex-ecve(2).  Starting with Linux 2.6.25, the system-wide capability              bounding set disappeared,  and  was  replaced  by  a  per-thread              bounding set; seecapabilities(7).       /proc/sys/kernel/core_pattern              Seecore(5).       /proc/sys/kernel/core_pipe_limit              Seecore(5).       /proc/sys/kernel/core_uses_pid              Seecore(5).       /proc/sys/kernel/ctrl-alt-del              This  file  controls  the handling of Ctrl-Alt-Del from the key-              board.  When the value  in  this  file  is  0,  Ctrl-Alt-Del  is              trapped  and  sent  to  theinit(1) program to handle a graceful              restart.  When the value is greater than zero, Linux's  reaction              to  a Vulcan Nerve Pinch (tm) will be an immediate reboot, with-              out even syncing its dirty buffers.  Note: when a program  (like              dosemu)  has the keyboard in "raw" mode, the ctrl-alt-del is in-              tercepted by the program before it ever reaches the  kernel  tty              layer, and it's up to the program to decide what to do with it.       /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)              The value in this file determines who can see kernel syslog con-              tents.  A value of 0 in this file imposes no  restrictions.   If              the  value  is 1, only privileged users can read the kernel sys-              log.  (Seesyslog(2) for more details.)  Since Linux  3.4,  only              users  with the CAP_SYS_ADMIN capability may change the value in              this file.       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname              can be used to set the NIS/YP domainname  and  the  hostname  of              your  box  in exactly the same way as the commandsdomainname(1)              andhostname(1), that is:                  # echo 'darkstar' > /proc/sys/kernel/hostname                  # echo 'mydomain' > /proc/sys/kernel/domainname              has the same effect as                  # hostname 'darkstar'                  # domainname 'mydomain'              Note, however, that the classic darkstar.frop.org has the  host-              name "darkstar" and DNS (Internet Domain Name Server) domainname              "frop.org", not to be confused with the NIS (Network Information              Service)  or  YP  (Yellow  Pages)  domainname.  These two domain              names are in general different.  For a detailed  discussion  see              thehostname(1) man page.       /proc/sys/kernel/hotplug              This  file  contains  the pathname for the hotplug policy agent.              The default value in this file is /sbin/hotplug.       /proc/sys/kernel/htab-reclaim (before Linux 2.4.9.2)              (PowerPC only) If this file is set to a nonzero value, the  Pow-              erPC  htab  (see kernel file Documentation/powerpc/ppc_htab.txt)              is pruned each time the system hits the idle loop.       /proc/sys/kernel/keys/*              This directory contains various files that define parameters and              limits  for  the  key-management  facility.  These files are de-              scribed inkeyrings(7).       /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)              The value in this file determines whether kernel  addresses  are              exposed  via  /proc files and other interfaces.  A value of 0 in              this file imposes no restrictions.  If the value  is  1,  kernel              pointers printed using the %pK format specifier will be replaced              with zeros unless the user has the  CAP_SYSLOG  capability.   If              the  value  is  2,  kernel pointers printed using the %pK format              specifier will be replaced with zeros regardless of  the  user's              capabilities.   The  initial  default value for this file was 1,              but the default was changed to 0 in Linux 2.6.39.   Since  Linux              3.4, only users with the CAP_SYS_ADMIN capability can change the              value in this file.       /proc/sys/kernel/l2cr              (PowerPC only) This file contains a flag that  controls  the  L2              cache of G3 processor boards.  If 0, the cache is disabled.  En-              abled if nonzero.       /proc/sys/kernel/modprobe              This file contains the pathname for the  kernel  module  loader.              The  default  value is /sbin/modprobe.  The file is present only              if the kernel is built with the CONFIG_MODULES  (CONFIG_KMOD  in              Linux  2.6.26  and  earlier) option enabled.  It is described by              the Linux kernel  source  file  Documentation/kmod.txt  (present              only in kernel 2.4 and earlier).       /proc/sys/kernel/modules_disabled (since Linux 2.6.31)              A toggle value indicating if modules are allowed to be loaded in              an otherwise modular kernel.  This toggle defaults to  off  (0),              but  can  be  set  true  (1).  Once true, modules can be neither              loaded nor unloaded, and the toggle cannot be set back to false.              The  file  is  present only if the kernel is built with the CON-              FIG_MODULES option enabled.       /proc/sys/kernel/msgmax (since Linux 2.2)              This file defines a system-wide  limit  specifying  the  maximum              number  of  bytes in a single message written on a System V mes-              sage queue.       /proc/sys/kernel/msgmni (since Linux 2.4)              This file defines the system-wide limit on the number of message              queue identifiers.  See also /proc/sys/kernel/auto_msgmni.       /proc/sys/kernel/msgmnb (since Linux 2.2)              This file defines a system-wide parameter used to initialize the              msg_qbytes setting for subsequently created message queues.  The              msg_qbytes  setting  specifies  the maximum number of bytes that              may be written to the message queue.       /proc/sys/kernel/ngroups_max (since Linux 2.6.4)              This is a read-only file that displays the upper  limit  on  the              number of a process's group memberships.       /proc/sys/kernel/ns_last_pid (since Linux 3.3)              Seepid_namespaces(7).       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease              These files give substrings of /proc/version.       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid              These  files  duplicate  the  files /proc/sys/fs/overflowgid and              /proc/sys/fs/overflowuid.       /proc/sys/kernel/panic              This  file  gives  read/write  access  to  the  kernel  variable              panic_timeout.   If  this  is  zero,  the  kernel will loop on a              panic; if nonzero, it indicates that the kernel  should  autore-              boot  after  this  number of seconds.  When you use the software              watchdog device driver, the recommended setting is 60.       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)              This file controls the kernel's behavior when an oops or BUG  is              encountered.   If this file contains 0, then the system tries to              continue operation.  If it contains 1, then the system delays  a              few  seconds  (to give klogd time to record the oops output) and              then panics.  If the /proc/sys/kernel/panic file  is  also  non-              zero, then the machine will be rebooted.       /proc/sys/kernel/pid_max (since Linux 2.5.34)              This  file  specifies the value at which PIDs wrap around (i.e.,              the value in this file is one greater  than  the  maximum  PID).              PIDs  greater than this value are not allocated; thus, the value              in this file also acts as a system-wide limit on the total  num-              ber  of processes and threads.  The default value for this file,              32768, results in the same range of PIDs as on earlier  kernels.              On 32-bit platforms, 32768 is the maximum value for pid_max.  On              64-bit systems, pid_max can be set  to  any  value  up  to  2^22              (PID_MAX_LIMIT, approximately 4 million).       /proc/sys/kernel/powersave-nap (PowerPC only)              This file contains a flag.  If set, Linux-PPC will use the "nap"              mode of powersaving, otherwise the "doze" mode will be used.       /proc/sys/kernel/printk              Seesyslog(2).       /proc/sys/kernel/pty (since Linux 2.6.4)              This directory contains two files relating to the number of UNIX              98 pseudoterminals (seepts(4)) on the system.       /proc/sys/kernel/pty/max              This file defines the maximum number of pseudoterminals.       /proc/sys/kernel/pty/nr              This  read-only file indicates how many pseudoterminals are cur-              rently in use.       /proc/sys/kernel/random              This directory contains various parameters controlling the oper-              ation of the file /dev/random.  Seerandom(4) for further infor-              mation.       /proc/sys/kernel/random/uuid (since Linux 2.4)              Each read from this read-only file returns a randomly  generated              128-bit UUID, as a string in the standard UUID format.       /proc/sys/kernel/randomize_va_space (since Linux 2.6.12)              Select  the address space layout randomization (ASLR) policy for              the system (on architectures that support ASLR).   Three  values              are supported for this file:              0  Turn  ASLR  off.   This is the default for architectures that                 don't support ASLR, and when the kernel is  booted  with  the                 norandmaps parameter.              1  Make the addresses ofmmap(2) allocations, the stack, and the                 VDSO page randomized.  Among other things,  this  means  that                 shared libraries will be loaded at randomized addresses.  The                 text segment of PIE-linked binaries will also be loaded at  a                 randomized  address.  This value is the default if the kernel                 was configured with CONFIG_COMPAT_BRK.              2  (Since Linux 2.6.25) Also support heap  randomization.   This                 value  is  the  default if the kernel was not configured with                 CONFIG_COMPAT_BRK.       /proc/sys/kernel/real-root-dev              This file is documented in the Linux kernel source file Documen-              tation/admin-guide/initrd.rst  (or  Documentation/initrd.txt be-              fore Linux 4.10).       /proc/sys/kernel/reboot-cmd (Sparc only)              This file seems to be a way to give an  argument  to  the  SPARC              ROM/Flash  boot  loader.   Maybe to tell it what to do after re-              booting?       /proc/sys/kernel/rtsig-max              (Only in kernels up to and including  2.6.7;  seesetrlimit(2))              This  file can be used to tune the maximum number of POSIX real-              time (queued) signals that can be outstanding in the system.       /proc/sys/kernel/rtsig-nr              (Only in kernels up to and including 2.6.7.)   This  file  shows              the number of POSIX real-time signals currently queued.       /proc/[pid]/sched_autogroup_enabled (since Linux 2.6.38)              Seesched(7).       /proc/sys/kernel/sched_child_runs_first (since Linux 2.6.23)              If this file contains the value zero, then, after afork(2), the              parent is first scheduled on the CPU.  If the  file  contains  a              nonzero  value,  then  the  child is scheduled first on the CPU.              (Of course, on a multiprocessor system, the parent and the child              might both immediately be scheduled on a CPU.)       /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)              Seesched_rr_get_interval(2).       /proc/sys/kernel/sched_rt_period_us (since Linux 2.6.25)              Seesched(7).       /proc/sys/kernel/sched_rt_runtime_us (since Linux 2.6.25)              Seesched(7).       /proc/sys/kernel/seccomp (since Linux 4.14)              This  directory provides additional seccomp information and con-              figuration.  Seeseccomp(2) for further details.       /proc/sys/kernel/sem (since Linux 2.4)              This file contains 4 numbers defining limits for  System  V  IPC              semaphores.  These fields are, in order:              SEMMSL  The maximum semaphores per semaphore set.              SEMMNS  A  system-wide  limit on the number of semaphores in all                      semaphore sets.              SEMOPM  The maximum number of operations that may  be  specified                      in asemop(2) call.              SEMMNI  A  system-wide  limit on the maximum number of semaphore                      identifiers.       /proc/sys/kernel/sg-big-buff              This file shows the size of the generic SCSI device (sg) buffer.              You  can't  tune it just yet, but you could change it at compile              time by editing include/scsi/sg.h  and  changing  the  value  of              SG_BIG_BUFF.   However,  there shouldn't be any reason to change              this value.       /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)              If this file is set to 1, all System V  shared  memory  segments              will be marked for destruction as soon as the number of attached              processes falls to zero; in other words, it is no longer  possi-              ble to create shared memory segments that exist independently of              any attached process.              The effect is as though ashmctl(2) IPC_RMID is performed on all              existing  segments as well as all segments created in the future              (until this file is reset to 0).  Note  that  existing  segments              that  are  attached  to no process will be immediately destroyed              when this file is set to 1.  Setting this option will  also  de-              stroy  segments that were created, but never attached, upon ter-              mination of the process that created the segment withshmget(2).              Setting this file to 1 provides a way of ensuring that all  Sys-              tem  V  shared  memory segments are counted against the resource              usage and resource limits (see the description of  RLIMIT_AS  ingetrlimit(2)) of at least one process.              Because  setting  this  file to 1 produces behavior that is non-              standard and could also break existing applications, the default              value  in this file is 0.  Set this file to 1 only if you have a              good understanding of the semantics of  the  applications  using              System V shared memory on your system.       /proc/sys/kernel/shmall (since Linux 2.2)              This  file contains the system-wide limit on the total number of              pages of System V shared memory.       /proc/sys/kernel/shmmax (since Linux 2.2)              This file can be used to query and set the run-time limit on the              maximum  (System  V  IPC) shared memory segment size that can be              created.  Shared memory segments up to 1GB are now supported  in              the kernel.  This value defaults to SHMMAX.       /proc/sys/kernel/shmmni (since Linux 2.4)              This  file  specifies the system-wide maximum number of System V              shared memory segments that can be created.       /proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)              The value in this file determines how the  file  offset  affects              the  behavior of updating entries in files under /proc/sys.  The              file has three possible values:              -1  This provides legacy  handling,  with  no  printk  warnings.                  Eachwrite(2)  must  fully contain the value to be written,                  and multiple writes on the same file descriptor  will  over-                  write the entire value, regardless of the file position.              0   (default)  This  provides  the  same behavior as for -1, but                  printk warnings  are  written  for  processes  that  perform                  writes when the file offset is not 0.              1   Respect  the file offset when writing strings into /proc/sys                  files.  Multiple writes will append  to  the  value  buffer.                  Anything written beyond the maximum length of the value buf-                  fer will be ignored.  Writes to  numeric  /proc/sys  entries                  must  always be at file offset 0 and the value must be fully                  contained in the buffer provided towrite(2).       /proc/sys/kernel/sysrq              This file controls the functions allowed to be  invoked  by  the              SysRq  key.   By default, the file contains 1 meaning that every              possible SysRq request is allowed  (in  older  kernel  versions,              SysRq was disabled by default, and you were required to specifi-              cally enable it at run-time, but this is not the case any more).              Possible values in this file are:              0    Disable sysrq completely              1    Enable all functions of sysrq              > 1  Bit mask of allowed sysrq functions, as follows:                     2  Enable control of console logging level                     4  Enable control of keyboard (SAK, unraw)                     8  Enable debugging dumps of processes etc.                    16  Enable sync command                    32  Enable remount read-only                    64  Enable signaling of processes (term, kill, oom-kill)                   128  Allow reboot/poweroff                   256  Allow nicing of all real-time tasks              This  file is present only if the CONFIG_MAGIC_SYSRQ kernel con-              figuration option is enabled.  For further details see the Linux              kernel source file Documentation/admin-guide/sysrq.rst (or Docu-              mentation/sysrq.txt before Linux 4.10).       /proc/sys/kernel/version              This file contains a string such as:                  #5 Wed Feb 25 21:49:24 MET 1998              The "#5" means that this is the fifth  kernel  built  from  this              source  base  and  the  date following it indicates the time the              kernel was built.       /proc/sys/kernel/threads-max (since Linux 2.3.11)              This file specifies the  system-wide  limit  on  the  number  of              threads (tasks) that can be created on the system.              Since Linux 4.1, the value that can be written to threads-max is              bounded.  The minimum value that can be written is 20.  The max-              imum  value  that  can  be  written is given by the constant FU-              TEX_TID_MASK (0x3fffffff).  If a value outside of this range  is              written to threads-max, the error EINVAL occurs.              The  value  written  is checked against the available RAM pages.              If the thread structures would occupy too much (more than 1/8th)              of the available RAM pages, threads-max is reduced accordingly.       /proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)              Seeptrace(2).       /proc/sys/kernel/zero-paged (PowerPC only)              This  file  contains  a flag.  When enabled (nonzero), Linux-PPC              will pre-zero pages in  the  idle  loop,  possibly  speeding  up              get_free_pages.       /proc/sys/net              This directory contains networking stuff.  Explanations for some              of the files under this directory can be  found  intcp(7)  andip(7).       /proc/sys/net/core/bpf_jit_enable              Seebpf(2).       /proc/sys/net/core/somaxconn              This  file  defines  a ceiling value for the backlog argument oflisten(2); see thelisten(2) manual page for details.       /proc/sys/proc              This directory may be empty.       /proc/sys/sunrpc              This directory supports Sun remote procedure  call  for  network              filesystem (NFS).  On some systems, it is not present.       /proc/sys/user (since Linux 4.9)              Seenamespaces(7).       /proc/sys/vm              This directory contains files for memory management tuning, buf-              fer and cache management.       /proc/sys/vm/admin_reserve_kbytes (since Linux 3.10)              This file defines the amount of free memory (in KiB) on the sys-              tem  that  should  be  reserved  for  users  with the capability              CAP_SYS_ADMIN.              The default value in this file is the minimum  of  [3%  of  free              pages,  8MiB] expressed as KiB.  The default is intended to pro-              vide enough for the superuser to log in and kill a  process,  if              necessary, under the default overcommit 'guess' mode (i.e., 0 in              /proc/sys/vm/overcommit_memory).              Systems  running  in  "overcommit  never"  mode  (i.e.,   2   in              /proc/sys/vm/overcommit_memory)  should  increase  the  value in              this file to account for the full virtual  memory  size  of  the              programs  used  to  recover  (e.g.,login(1)ssh(1), andtop(1))              Otherwise, the superuser may not be able to log  in  to  recover              the  system.   For example, on x86-64 a suitable value is 131072              (128MiB reserved).              Changing the value in this file takes effect whenever an  appli-              cation requests memory.       /proc/sys/vm/compact_memory (since Linux 2.6.35)              When  1  is  written  to this file, all zones are compacted such              that free memory is available in contiguous blocks where  possi-              ble.   The  effect  of  this  action  can  be  seen by examining              /proc/buddyinfo.              Present only if  the  kernel  was  configured  with  CONFIG_COM-              PACTION.       /proc/sys/vm/drop_caches (since Linux 2.6.16)              Writing  to  this  file  causes the kernel to drop clean caches,              dentries, and inodes from memory, causing that memory to  become              free.  This can be useful for memory management testing and per-              forming reproducible filesystem benchmarks.  Because writing  to              this  file causes the benefits of caching to be lost, it can de-              grade overall system performance.              To free pagecache, use:                  echo 1 > /proc/sys/vm/drop_caches              To free dentries and inodes, use:                  echo 2 > /proc/sys/vm/drop_caches              To free pagecache, dentries and inodes, use:                  echo 3 > /proc/sys/vm/drop_caches              Because writing to this file is a nondestructive  operation  and              dirty  objects  are  not  freeable,  the user should runsync(1)              first.       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)              If nonzero, this disables the new 32-bit memory-mapping  layout;              the kernel will use the legacy (2.4) layout for all processes.       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)              Control  how  to kill processes when an uncorrected memory error              (typically a 2-bit error in a memory module) that cannot be han-              dled  by  the  kernel is detected in the background by hardware.              In some cases (like the page still having a valid copy on disk),              the kernel will handle the failure transparently without affect-              ing any applications.  But if there is no other up-to-date  copy              of  the data, it will kill processes to prevent any data corrup-              tions from propagating.              The file has one of the following values:              1:  Kill all processes that have  the  corrupted-and-not-reload-                  able  page  mapped  as  soon  as the corruption is detected.                  Note that this is not supported for a few  types  of  pages,                  such  as kernel internally allocated data or the swap cache,                  but works for the majority of user pages.              0:  Unmap the corrupted page  from  all  processes  and  kill  a                  process only if it tries to access the page.              The  kill is performed using a SIGBUS signal with si_code set to              BUS_MCEERR_AO.  Processes can handle this if they want  to;  seesigaction(2) for more details.              This  feature is active only on architectures/platforms with ad-              vanced machine check handling and depends on the hardware  capa-              bilities.              Applications  can override the memory_failure_early_kill setting              individually with theprctl(2) PR_MCE_KILL operation.              Present only if  the  kernel  was  configured  with  CONFIG_MEM-              ORY_FAILURE.       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)              Enable memory failure recovery (when supported by the platform)              1:  Attempt recovery.              0:  Always panic on a memory failure.              Present  only  if  the  kernel  was  configured with CONFIG_MEM-              ORY_FAILURE.       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)              Enables a system-wide task dump (excluding kernel threads) to be              produced  when the kernel performs an OOM-killing.  The dump in-              cludes  the  following  information  for  each   task   (thread,              process): thread ID, real user ID, thread group ID (process ID),              virtual memory size, resident set size, the CPU that the task is              scheduled   on,   oom_adj   score   (see   the   description  of              /proc/[pid]/oom_adj), and command name.  This is helpful to  de-              termine why the OOM-killer was invoked and to identify the rogue              task that caused it.              If this contains the value zero, this information is suppressed.              On  very  large  systems  with thousands of tasks, it may not be              feasible to dump the memory  state  information  for  each  one.              Such systems should not be forced to incur a performance penalty              in OOM situations when the information may not be desired.              If this is set to nonzero, this information  is  shown  whenever              the OOM-killer actually kills a memory-hogging task.              The default value is 0.       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)              This enables or disables killing the OOM-triggering task in out-              of-memory situations.              If this is set to zero, the OOM-killer will scan through the en-              tire  tasklist  and  select  a task based on heuristics to kill.              This normally selects a rogue memory-hogging task that frees  up              a large amount of memory when killed.              If  this is set to nonzero, the OOM-killer simply kills the task              that triggered the out-of-memory condition.  This avoids a  pos-              sibly expensive tasklist scan.              If  /proc/sys/vm/panic_on_oom  is  nonzero,  it takes precedence              over whatever value is  used  in  /proc/sys/vm/oom_kill_allocat-              ing_task.              The default value is 0.       /proc/sys/vm/overcommit_kbytes (since Linux 3.14)              This writable file provides an alternative to /proc/sys/vm/over-              commit_ratio    for    controlling    the    CommitLimit    when              /proc/sys/vm/overcommit_memory  has  the value 2.  It allows the              amount of memory overcommitting to be specified as  an  absolute              value  (in  kB),  rather  than  as a percentage, as is done with              overcommit_ratio.  This allows for finer-grained control of Com-              mitLimit on systems with extremely large memory sizes.              Only  one  of  overcommit_kbytes or overcommit_ratio can have an              effect: if overcommit_kbytes has a nonzero  value,  then  it  is              used  to  calculate  CommitLimit,  otherwise overcommit_ratio is              used.  Writing a value to either of these files causes the value              in the other file to be set to zero.       /proc/sys/vm/overcommit_memory              This  file  contains  the kernel virtual memory accounting mode.              Values are:                     0: heuristic overcommit (this is the default)                     1: always overcommit, never check                     2: always check, never overcommit              In mode 0, calls ofmmap(2) with MAP_NORESERVE are not  checked,              and  the default check is very weak, leading to the risk of get-              ting a process "OOM-killed".              In mode 1, the kernel pretends there is  always  enough  memory,              until  memory  actually runs out.  One use case for this mode is              scientific computing applications that employ large  sparse  ar-              rays.   In Linux kernel versions before 2.6.0, any nonzero value              implies mode 1.              In mode 2 (available since Linux 2.6), the total virtual address              space  that  can  be allocated (CommitLimit in /proc/meminfo) is              calculated as                  CommitLimit = (total_RAM - total_huge_TLB) *                                overcommit_ratio / 100 + total_swap              where:                   *  total_RAM is the total amount of RAM on the system;                   *  total_huge_TLB is the amount of  memory  set  aside  for                      huge pages;                   *  overcommit_ratio  is  the value in /proc/sys/vm/overcom-                      mit_ratio; and                   *  total_swap is the amount of swap space.              For example, on a system with 16GB  of  physical  RAM,  16GB  of              swap,  no space dedicated to huge pages, and an overcommit_ratio              of 50, this formula yields a CommitLimit of 24GB.              Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes              is nonzero, then CommitLimit is instead calculated as:                  CommitLimit = overcommit_kbytes + total_swap              See  also  the  description of /proc/sys/vm/admin_reserve_kbytes              and /proc/sys/vm/user_reserve_kbytes.       /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)              This writable file defines a percentage by which memory  can  be              overcommitted.   The  default  value in the file is 50.  See the              description of /proc/sys/vm/overcommit_memory.       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)              This enables or disables a kernel panic in an out-of-memory sit-              uation.              If this file is set to the value 0, the kernel's OOM-killer will              kill some rogue process.  Usually, the  OOM-killer  is  able  to              kill a rogue process and the system will survive.              If  this  file  is  set to the value 1, then the kernel normally              panics when out-of-memory happens.  However, if a process limits              allocations  to  certain  nodes  using memory policies (mbind(2)              MPOL_BIND) or cpusets (cpuset(7)) and those nodes  reach  memory              exhaustion  status, one process may be killed by the OOM-killer.              No panic occurs in this case: because other nodes' memory may be              free,  this  means the system as a whole may not have reached an              out-of-memory situation yet.              If this file is set to the value 2,  the  kernel  always  panics              when an out-of-memory condition occurs.              The default value is 0.  1 and 2 are for failover of clustering.              Select either according to your policy of failover.       /proc/sys/vm/swappiness              The value in this file controls how aggressively the kernel will              swap memory pages.  Higher values increase aggressiveness, lower              values decrease aggressiveness.  The default value is 60.       /proc/sys/vm/user_reserve_kbytes (since Linux 3.10)              Specifies an amount of memory (in KiB) to reserve for user  pro-              cesses,  This is intended to prevent a user from starting a sin-              gle memory hogging process, such that they cannot recover  (kill              the  hog).   The  value  in  this  file  has an effect only when              /proc/sys/vm/overcommit_memory is set to 2  ("overcommit  never"              mode).   In  this  case, the system reserves an amount of memory              that is the minimum of [3% of  current  process  size,  user_re-              serve_kbytes].              The  default  value  in  this file is the minimum of [3% of free              pages, 128MiB] expressed as KiB.              If the value in this file is set to zero, then a  user  will  be              allowed to allocate all free memory with a single process (minus              the amount reserved by /proc/sys/vm/admin_reserve_kbytes).   Any              subsequent  attempts  to execute a command will result in "fork:              Cannot allocate memory".              Changing the value in this file takes effect whenever an  appli-              cation requests memory.       /proc/sys/vm/unprivileged_userfaultfd (since Linux 5.2)              This  (writable)  file  exposes a flag that controls whether un-              privileged processes are allowed to employuserfaultfd(2).   If              this  file  has the value 1, then unprivileged processes may useuserfaultfd(2).  If this file has the value 0,  then  only  pro-              cesses  that have the CAP_SYS_PTRACE capability may employ user-faultfd(2).  The default value in this file is 1.       /proc/sysrq-trigger (since Linux 2.4.21)              Writing a character to this file triggers the same  SysRq  func-              tion  as  typing  ALT-SysRq-<character>  (see the description of              /proc/sys/kernel/sysrq).  This file is normally writable only by              root.  For further details see the Linux kernel source file Doc-              umentation/admin-guide/sysrq.rst (or Documentation/sysrq.txt be-              fore Linux 4.10).       /proc/sysvipc              Subdirectory  containing  the  pseudo-files  msg,  sem  and shm.              These files list the System V Interprocess  Communication  (IPC)              objects  (respectively:  message  queues, semaphores, and shared              memory) that currently exist on the  system,  providing  similar              information  to  that  available  viaipcs(1).  These files have              headers and are formatted (one IPC object per line) for easy un-              derstanding.sysvipc(7) provides further background on the in-              formation shown by these files.       /proc/thread-self (since Linux 3.17)              This directory refers to the thread accessing the /proc filesys-              tem,  and  is  identical  to the /proc/self/task/[tid] directory              named by the process thread ID ([tid]) of the same thread.       /proc/timer_list (since Linux 2.6.21)              This read-only file exposes a  list  of  all  currently  pending              (high-resolution) timers, all clock-event sources, and their pa-              rameters in a human-readable form.       /proc/timer_stats (from  Linux 2.6.21 until Linux 4.10)              This is a debugging facility to make timer (ab)use  in  a  Linux              system  visible  to kernel and user-space developers.  It can be              used by kernel and user-space developers to  verify  that  their              code  does  not  make undue use of timers.  The goal is to avoid              unnecessary wakeups, thereby optimizing power consumption.              If enabled in the kernel (CONFIG_TIMER_STATS), but not used,  it              has  almost  zero run-time overhead and a relatively small data-              structure overhead.  Even if collection is enabled at run  time,              overhead  is  low:  all  the  locking  is  per-CPU and lookup is              hashed.              The /proc/timer_stats file is used both to control sampling  fa-              cility and to read out the sampled information.              The timer_stats functionality is inactive on bootup.  A sampling              period can be started using the following command:                  # echo 1 > /proc/timer_stats              The following command stops a sampling period:                  # echo 0 > /proc/timer_stats              The statistics can be retrieved by:                  $ cat /proc/timer_stats              While sampling is enabled, each readout  from  /proc/timer_stats              will  see  newly updated statistics.  Once sampling is disabled,              the sampled information is kept until a  new  sample  period  is              started.  This allows multiple readouts.              Sample output from /proc/timer_stats:    $ cat /proc/timer_stats    Timer Stats Version: v0.3    Sample period: 1.764 s    Collection: active      255,     0 swapper/3        hrtimer_start_range_ns (tick_sched_timer)       71,     0 swapper/1        hrtimer_start_range_ns (tick_sched_timer)       58,     0 swapper/0        hrtimer_start_range_ns (tick_sched_timer)        4,  1694 gnome-shell      mod_delayed_work_on (delayed_work_timer_fn)       17,     7 rcu_sched        rcu_gp_kthread (process_timeout)    ...        1,  4911 kworker/u16:0    mod_delayed_work_on (delayed_work_timer_fn)       1D,  2522 kworker/0:0      queue_delayed_work_on (delayed_work_timer_fn)    1029 total events, 583.333 events/sec              The output columns are:              *  a  count  of  the  number  of events, optionally (since Linux                 2.6.23) followed by the letter 'D' if this  is  a  deferrable                 timer;              *  the PID of the process that initialized the timer;              *  the name of the process that initialized the timer;              *  the function where the timer was initialized; and              *  (in  parentheses)  the  callback  function that is associated                 with the timer.              During the Linux 4.11 development cycle, this file  was  removed              because  of  security concerns, as it exposes information across              namespaces.  Furthermore, it is possible to obtain the same  in-              formation via in-kernel tracing facilities such as ftrace.       /proc/tty              Subdirectory  containing the pseudo-files and subdirectories for              tty drivers and line disciplines.       /proc/uptime              This file contains two numbers (values in seconds):  the  uptime              of  the  system (including time spent in suspend) and the amount              of time spent in the idle process.       /proc/version              This string identifies the kernel version that is currently run-              ning.   It  includes  the  contents  of /proc/sys/kernel/ostype,              /proc/sys/kernel/osrelease  and  /proc/sys/kernel/version.   For              example:        Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994       /proc/vmstat (since Linux 2.6.0)              This file displays various virtual memory statistics.  Each line              of this file contains a single  name-value  pair,  delimited  by              white space.  Some lines are present only if the kernel was con-              figured with suitable options.  (In some cases, the options  re-              quired for particular files have changed across kernel versions,              so they are not listed here.  Details can be found by consulting              the kernel source code.)  The following fields may be present:              nr_free_pages (since Linux 2.6.31)              nr_alloc_batch (since Linux 3.12)              nr_inactive_anon (since Linux 2.6.28)              nr_active_anon (since Linux 2.6.28)              nr_inactive_file (since Linux 2.6.28)              nr_active_file (since Linux 2.6.28)              nr_unevictable (since Linux 2.6.28)              nr_mlock (since Linux 2.6.28)              nr_anon_pages (since Linux 2.6.18)              nr_mapped (since Linux 2.6.0)              nr_file_pages (since Linux 2.6.18)              nr_dirty (since Linux 2.6.0)              nr_writeback (since Linux 2.6.0)              nr_slab_reclaimable (since Linux 2.6.19)              nr_slab_unreclaimable (since Linux 2.6.19)              nr_page_table_pages (since Linux 2.6.0)              nr_kernel_stack (since Linux 2.6.32)                     Amount of memory allocated to kernel stacks.              nr_unstable (since Linux 2.6.0)              nr_bounce (since Linux 2.6.12)              nr_vmscan_write (since Linux 2.6.19)              nr_vmscan_immediate_reclaim (since Linux 3.2)              nr_writeback_temp (since Linux 2.6.26)              nr_isolated_anon (since Linux 2.6.32)              nr_isolated_file (since Linux 2.6.32)              nr_shmem (since Linux 2.6.32)                     Pages used by shmem andtmpfs(5).              nr_dirtied (since Linux 2.6.37)              nr_written (since Linux 2.6.37)              nr_pages_scanned (since Linux 3.17)              numa_hit (since Linux 2.6.18)              numa_miss (since Linux 2.6.18)              numa_foreign (since Linux 2.6.18)              numa_interleave (since Linux 2.6.18)              numa_local (since Linux 2.6.18)              numa_other (since Linux 2.6.18)              workingset_refault (since Linux 3.15)              workingset_activate (since Linux 3.15)              workingset_nodereclaim (since Linux 3.15)              nr_anon_transparent_hugepages (since Linux 2.6.38)              nr_free_cma (since Linux 3.7)                     Number of free CMA (Contiguous Memory Allocator) pages.              nr_dirty_threshold (since Linux 2.6.37)              nr_dirty_background_threshold (since Linux 2.6.37)              pgpgin (since Linux 2.6.0)              pgpgout (since Linux 2.6.0)              pswpin (since Linux 2.6.0)              pswpout (since Linux 2.6.0)              pgalloc_dma (since Linux 2.6.5)              pgalloc_dma32 (since Linux 2.6.16)              pgalloc_normal (since Linux 2.6.5)              pgalloc_high (since Linux 2.6.5)              pgalloc_movable (since Linux 2.6.23)              pgfree (since Linux 2.6.0)              pgactivate (since Linux 2.6.0)              pgdeactivate (since Linux 2.6.0)              pgfault (since Linux 2.6.0)              pgmajfault (since Linux 2.6.0)              pgrefill_dma (since Linux 2.6.5)              pgrefill_dma32 (since Linux 2.6.16)              pgrefill_normal (since Linux 2.6.5)              pgrefill_high (since Linux 2.6.5)              pgrefill_movable (since Linux 2.6.23)              pgsteal_kswapd_dma (since Linux 3.4)              pgsteal_kswapd_dma32 (since Linux 3.4)              pgsteal_kswapd_normal (since Linux 3.4)              pgsteal_kswapd_high (since Linux 3.4)              pgsteal_kswapd_movable (since Linux 3.4)              pgsteal_direct_dma              pgsteal_direct_dma32 (since Linux 3.4)              pgsteal_direct_normal (since Linux 3.4)              pgsteal_direct_high (since Linux 3.4)              pgsteal_direct_movable (since Linux 2.6.23)              pgscan_kswapd_dma              pgscan_kswapd_dma32 (since Linux 2.6.16)              pgscan_kswapd_normal (since Linux 2.6.5)              pgscan_kswapd_high              pgscan_kswapd_movable (since Linux 2.6.23)              pgscan_direct_dma              pgscan_direct_dma32 (since Linux 2.6.16)              pgscan_direct_normal              pgscan_direct_high              pgscan_direct_movable (since Linux 2.6.23)              pgscan_direct_throttle (since Linux 3.6)              zone_reclaim_failed (since linux 2.6.31)              pginodesteal (since linux 2.6.0)              slabs_scanned (since linux 2.6.5)              kswapd_inodesteal (since linux 2.6.0)              kswapd_low_wmark_hit_quickly (since 2.6.33)              kswapd_high_wmark_hit_quickly (since 2.6.33)              pageoutrun (since Linux 2.6.0)              allocstall (since Linux 2.6.0)              pgrotated (since Linux 2.6.0)              drop_pagecache (since Linux 3.15)              drop_slab (since Linux 3.15)              numa_pte_updates (since Linux 3.8)              numa_huge_pte_updates (since Linux 3.13)              numa_hint_faults (since Linux 3.8)              numa_hint_faults_local (since Linux 3.8)              numa_pages_migrated (since Linux 3.8)              pgmigrate_success (since Linux 3.8)              pgmigrate_fail (since Linux 3.8)              compact_migrate_scanned (since Linux 3.8)              compact_free_scanned (since Linux 3.8)              compact_isolated (since Linux 3.8)              compact_stall (since Linux 2.6.35)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              compact_fail (since Linux 2.6.35)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              compact_success (since Linux 2.6.35)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              htlb_buddy_alloc_success (since Linux 2.6.26)              htlb_buddy_alloc_fail (since Linux 2.6.26)              unevictable_pgs_culled (since Linux 2.6.28)              unevictable_pgs_scanned (since Linux 2.6.28)              unevictable_pgs_rescued (since Linux 2.6.28)              unevictable_pgs_mlocked (since Linux 2.6.28)              unevictable_pgs_munlocked (since Linux 2.6.28)              unevictable_pgs_cleared (since Linux 2.6.28)              unevictable_pgs_stranded (since Linux 2.6.28)              thp_fault_alloc (since Linux 2.6.39)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              thp_fault_fallback (since Linux 2.6.39)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              thp_collapse_alloc (since Linux 2.6.39)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              thp_collapse_alloc_failed (since Linux 2.6.39)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              thp_split (since Linux 2.6.39)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              thp_zero_page_alloc (since Linux 3.8)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              thp_zero_page_alloc_failed (since Linux 3.8)                     See   the   kernel   source   file   Documentation/admin-                     guide/mm/transhuge.rst.              balloon_inflate (since Linux 3.18)              balloon_deflate (since Linux 3.18)              balloon_migrate (since Linux 3.18)              nr_tlb_remote_flush (since Linux 3.12)              nr_tlb_remote_flush_received (since Linux 3.12)              nr_tlb_local_flush_all (since Linux 3.12)              nr_tlb_local_flush_one (since Linux 3.12)              vmacache_find_calls (since Linux 3.16)              vmacache_find_hits (since Linux 3.16)              vmacache_full_flushes (since Linux 3.19)       /proc/zoneinfo (since Linux 2.6.13)              This  file display information about memory zones.  This is use-              ful for analyzing virtual memory behavior.NOTES       Many files contain strings (e.g., the  environment  and  command  line)       that  are  in  the  internal  format, with subfields terminated by null       bytes ('\0').  When inspecting such files, you may find  that  the  re-       sults  are  more readable if you use a command of the following form to       display them:           $ cat file | tr '\000' '\n'       This manual page is incomplete, possibly inaccurate, and is the kind of       thing that needs to be updated very often.SEE ALSOcat(1),dmesg(1),find(1),free(1),htop(1),init(1),ps(1),pstree(1),tr(1),uptime(1),chroot(2),mmap(2),readlink(2),syslog(2),slabinfo(5),sysfs(5),hier(7),namespaces(7),time(7),arp(8), hd-parm(8),ifconfig(8),lsmod(8),lspci(8),mount(8),netstat(8),procinfo(8),route(8),sysctl(8)       The Linux kernel source files: Documentation/filesystems/proc.txt, Doc-       umentation/sysctl/fs.txt,  Documentation/sysctl/kernel.txt,  Documenta-       tion/sysctl/net.txt, and Documentation/sysctl/vm.txt.COLOPHON       This  page  is  part of release 5.05 of the Linux man-pages project.  A       description of the project, information about reporting bugs,  and  the       latest     version     of     this    page,    can    be    found    at       https://www.kernel.org/doc/man-pages/.Linux                             2019-11-19PROC(5)