v9fs: Plan 9 Resource Sharing for Linux¶
About¶
v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
This software was originally developed by Ron Minnich <rminnich@sandia.gov>and Maya Gokhale. Additional development by Greg Watson<gwatson@lanl.gov> and most recently Eric Van Hensbergen<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox<rsc@swtch.com>.
The best detailed explanation of the Linux implementation and applications ofthe 9p client is available in the form of a USENIX paper:
Other applications are described in the following papers:
- XCPU & Clusteringhttp://xcpu.org/papers/xcpu-talk.pdf
- KVMFS: control file system for KVMhttp://xcpu.org/papers/kvmfs.pdf
- CellFS: A New Programming Model for the Cell BEhttp://xcpu.org/papers/cellfs-talk.pdf
- PROSE I/O: Using 9p to enable Application Partitionshttp://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf
- VirtFS: A Virtualization Aware File System pass-throughhttp://goo.gl/3WPDg
Usage¶
For remote file server:
mount -t 9p 10.10.1.2 /mnt/9
For Plan 9 From User Space applications (http://swtch.com/plan9):
mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER
For server running on QEMU host with virtio transport:
mount -t 9p -o trans=virtio <mount_tag> /mnt/9
where mount_tag is the tag associated by the server to each of the exportedmount points. Each 9P export is seen by the client as a virtio device with anassociated “mount_tag” property. Available mount tags can beseen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
Options¶
trans=name select an alternative transport. Valid options arecurrently:
unix specifying a named pipe mount point tcp specifying a normal TCP/IP connection fd used passed file descriptors for connection(see rfdno and wfdno) virtio connect to the next virtio channel available(from QEMU with trans_virtio module) rdma connect to a specified RDMA channel uname=name user name to attempt mount as on the remote server. Theserver may override or ignore this value. Certain usernames may require authentication. aname=name aname specifies the file tree to access when the server isoffering several exported file systems. cache=mode specifies a caching policy. By default, no caches are used.
- none
- default no cache policy, metadata and dataalike are synchronous.
- loose
- no attempts are made at consistency,intended for exclusive, read-only mounts
- fscache
- use FS-Cache for a persistent, read-onlycache backend.
- mmap
- minimal cache that is only used for read-writemmap. Northing else is cached, like cache=none
debug=n specifies debug level. The debug level is a bitmask.
0x01 display verbose error messages 0x02 developer debug (DEBUG_CURRENT) 0x04 display 9p trace 0x08 display VFS trace 0x10 display Marshalling debug 0x20 display RPC debug 0x40 display transport debug 0x80 display allocation debug 0x100 display protocol message debug 0x200 display Fid debug 0x400 display packet debug 0x800 display fscache tracing debug rfdno=n the file descriptor for reading with trans=fd wfdno=n the file descriptor for writing with trans=fd msize=n the number of bytes to use for 9p packet payload port=n port to connect to on the remote server noextend force legacy mode (no 9p2000.u or 9p2000.L semantics) version=name Select 9P protocol version. Valid options are:
9p2000 Legacy mode (same as noextend) 9p2000.u Use 9P2000.u protocol 9p2000.L Use 9P2000.L protocol dfltuid attempt to mount as a particular uid dfltgid attempt to mount with a particular gid afid security channel - used by Plan 9 authentication protocols nodevmap do not map special files - represent them as normal files.This can be used to share devices/named pipes/sockets betweenhosts. This functionality will be expanded in later versions. access
- there are four access modes.
- user
- if a user tries to access a file on v9fsfilesystem for the first time, v9fs sends anattach command (Tattach) for that user.This is the default mode.
- <uid>
- allows only user with uid=<uid> to accessthe files on the mounted filesystem
- any
- v9fs does single attach and performs alloperations as one user
- clien
- ACL based access check on the 9p clientside for access validation
cachetag cache tag to use the specified persistent cache.cache tags for existing cache sessions can be listed at/sys/fs/9p/caches. (applies only to cache=fscache)
Behavior¶
This section aims at describing 9p ‘quirks’ that can be differentfrom a local filesystem behaviors.
- Setting O_NONBLOCK on a file will make client reads return as earlyas the server returns some data instead of trying to fill the readbuffer with the requested amount of bytes or end of file is reached.
Resources¶
Protocol specifications are maintained on github:http://ericvh.github.com/9p-rfc/
9p client and server implementations are listed onhttp://9p.cat-v.org/implementations
A 9p2000.L server is being developed by LLNL and can be foundathttp://code.google.com/p/diod/
There are user and developer mailing lists available through the v9fs projecton sourceforge (http://sourceforge.net/projects/v9fs).
News and other information is maintained on a Wiki.(http://sf.net/apps/mediawiki/v9fs/index.php).
Bug reports are best issued via the mailing list.
For more information on the Plan 9 Operating System check outhttp://plan9.bell-labs.com/plan9
For information on Plan 9 from User Space (Plan 9 applications and librariesported to Linux/BSD/OSX/etc) check outhttps://9fans.github.io/plan9port/