Movatterモバイル変換

Network Working Group                                         P. DeutschRequest for Comments: 1635                                     A. EmtageFYI: 24                                                           BunyipCategory: Informational                                        A. Marine                                                               NASA NAIC                                                                May 1994How to Use Anonymous FTPStatus of this Memo   This memo provides information for the Internet community.  This memo   does not specify an Internet standard of any kind.  Distribution of   this memo is unlimited.Abstract   This document provides information for the novice Internet user about   using the File Transfer Protocol (FTP).  It explains what FTP is,   what anonymous FTP is, and what an anonymous FTP archive site is.  It   shows a sample anonymous FTP session.  It also discusses common ways   files are packaged for efficient storage and transmission.Acknowledgements   This document is the result of work done in the Internet Anonymous   FTP Archives (IAFA) working group of the IETF.  Special thanks are   due to Mark Baushke (Cisco), John Curran (BBN), Aydin Edguer (CWRU),   Rafal Maszkowski (Onsala Space Observatory), Marsha Perrott   (PREPnet), Bob Peterson (Texas Instruments), Nathan Torkington   (Victoria University of Wellington), and Stephen Tihor (NYU) for   excellent comments and contributions.What is FTP?   FTP refers to the File Transfer Protocol [1], one of the protocols   within the TCP/IP protocol suite used on the Internet.  The File   Transfer Protocol makes it possible to transfer files from one   computer (or host) on the Internet to another.  There are many FTP   implementations built on the specification of the FTP protocol.  A   user of an FTP program must log in to both hosts in order to transfer   a file from one to the other.   It is common for a user with files on more than one host to use the   FTP program to transfer files from one host to another.  In this   case, the user has an account on both hosts involved, so he has   passwords for both hosts.IAFA Working Group                                              [Page 1]

RFC 1635                       How To FTP                       May 1994   However, Internet users may also take advantage of a wealth of   information available from archive sites by using a general purpose   account called "anonymous FTP".What is an Archive Site?   An archive site is a host that acts as a repository of information,   much like a conventional library.  Information stored on these   Internet hosts is made available for users to transfer to their local   sites.  Users run software to identify this information and transfer   it to their own hosts.  Such a transfer is done with a program that   implements the File Transfer Protocol (FTP).What is Anonymous FTP?   Anonymous FTP is a means by which archive sites allow general access   to their archives of information.  These sites create a special   account called "anonymous".  User "anonymous" has limited access   rights to the archive host, as well as some operating restrictions.   In fact, the only operations allowed are logging in using FTP,   listing the contents of a limited set of directories, and retrieving   files.  Some sites limit the contents of a directory listing an   anonymous user can see as well.  Note that "anonymous" users are not   usually allowed to transfer files TO the archive site, but can only   retrieve files from such a site.   Traditionally, this special anonymous user account accepts any string   as a password, although it is common to use either the password   "guest" or one's electronic mail (e-mail) address.  Some archive   sites now explicitly ask for the user's e-mail address and will not   allow login with the "guest" password.  Providing an e-mail address   is a courtesy that allows archive site operators to get some idea of   who is using their services.What Information Do You Need to Know?   To retrieve a specific file, a user needs to know what host it is on,   and the pathname of the file.  A pathname tells the directory (and   possibly subdirectories) that house the file, and the name of the   file.  Often discussions of available files will not specifically   say, "This file is available for anonymous FTP from X host with Y   pathname".  However, if a file is publicly announced as available and   referred to as something like pub/good-stuff on nisc.sri.com, it is a   good assumption that you can try to transfer it.   You may also need to know if your machine uses an ASCII, EBCDIC, or   other character set to know how likely a transfer of binary   information will work, or whether such a transfer will require otherIAFA Working Group                                              [Page 2]

RFC 1635                       How To FTP                       May 1994   keywords, such as is true for TENEX.   In the general case, you may assume that an ASCII transfer will   always do the right thing for plain text files.  However, more and   more information is being stored in various compressed formats (which   are discussed later in this document), so knowing the binary   characteristics of your machine may be important.A Sample Session   To start an FTP session on a UNIX or VMS host, you type "ftp" and the   host name or host IP address of the machine to which you want to   connect.  For example, if you wish to access the NASA Network   Applications and Information Center archive site, you would normally   execute one of the following commands at the UNIX prompt:           ftp naic.nasa.gov   or           ftp 128.102.128.6   Observe that the first form uses the fully-qualified domain name and   the second uses the Internet address for the same host.   The following is an example of connecting to the naic.nasa.gov host   to retrieve STD 9,RFC 959, "File Transfer Protocol (FTP)" [1].   Note several things about the session.    1. Every response the FTP program at the archive site gives       is preceded by a number.  These numbers are called       Reply Codes and are defined in the FTP specification,RFC 959.  The text that accompanies these reply codes       can vary in different FTP implementations, and usually does.       Also note that some FTP client implementations (e.g., MVS       systems) may not echo the reply codes or text as       transmitted from the remote host.  They may generate their       own status lines or just hide the non-fatal replies       from you.  For the purposes of this document, the more       popular UNIX interface to the FTP client will be       presented.    2. The password you type is never shown on your screen.    3. It is possible to "browse" in archives, but most often users       already know the pathname of the file they want.  The pathname       forRFC 959 on this host is files/rfc/rfc959.txt.  In theIAFA Working Group                                              [Page 3]

RFC 1635                       How To FTP                       May 1994       example, we first connect to the 'files/rfc' directory (cd       files/rfc), then get the specific file we know we want.  If you       do not know the name of the file you want, a file called README       or something similar (00README.1ST, AAREAD.ME, INDEX, etc.) is       probably the one to retrieve first.   atlas.arc.nasa.gov% ftp naic.nasa.gov   Connected to naic.nasa.gov.   220 naic.nasa.gov FTP server (Wed May 4 12:15:15 PDT 1994) ready.   Name (naic.nasa.gov:amarine): anonymous   331 Guest login ok, send your complete e-mail address as password.   Password:   230-----------------------------------------------------------------   230-Welcome to the NASA Network Applications and Info Center Archive   230-   230-     Access to NAIC's online services is also available through:   230-   230-        Gopher         - naic.nasa.gov (port 70)   230-    World-Wide-Web -http://naic.nasa.gov/naic/naic-home.html   230-   230-        If you experience any problems please send email to   230-   230-                    naic@nasa.gov   230-   230-                 or call +1 (800) 858-9947   230-----------------------------------------------------------------   230-   230-Please read the file README   230-  it was last modified on Fri Dec 10 13:06:33 1993 - 165 days ago   230 Guest login ok, access restrictions apply.   ftp> cd files/rfc   250-Please read the file README.rfc250-  it was last modified on Fri Jul 30 16:47:29 1993 - 298 days ago   250 CWD command successful.   ftp> getrfc959.txt   200 PORT command successful.   150 Opening ASCII mode data connection forrfc959.txt (147316 bytes).   226 Transfer complete.   local:rfc959.txt remote:rfc959.txt   151249 bytes received in 0.9 seconds (1.6e+02 Kbytes/s)   ftp> quit   221 Goodbye.   atlas.arc.nasa.gov%IAFA Working Group                                              [Page 4]

RFC 1635                       How To FTP                       May 1994Variations   The above example is of the FTP program available on UNIX systems.   Other operating systems also make FTP programs available.  The actual   commands you type may vary somewhat with other programs.  However, in   general, you will do the following with every FTP program:     - Log in to your local host, and invoke the FTP program.     - Open a connection to the host (using either the host name       or its IP address)     - Once connected to the remote host, log in with username       "anonymous".     - Provide either the password "guest" or whatever the password the       site requests.     - Issue whatever FTP commands you require, such as those to       change directories or to retrieve a file.     - When finished, exit the FTP program, which will close your       connection to the archive host.Friendly Servers   These days, many sites are using a form of FTP that allows them to   display several lines of explanatory text that help direct users   through their archive.  The listing of alternative services on   naic.nasa.gov is an example.  If these effusive servers confuse the   client you are using, try typing a hyphen ( - ) before your password   when you log in.  That should disable the verbose mode of the server.Other FTP Commands   We have demonstrated some of the commands available with FTP   programs.  Many others are possible.  For example, once you have   logged in to a remote host:     - You may ask the FTP program to display a list of available       commands, typically by invoking the FTP program without       arguments and typing "help".     - You may view the contents of the directory to which you are       connected.  Type "dir" or "ls" to do so.     - You may rename a file by using the "get" command's       optional local file name, which follows the remote fileIAFA Working Group                                              [Page 5]

RFC 1635                       How To FTP                       May 1994       name on the command line.  You probably should rename a       file when the remote file name exceeds your local file       system's naming constraints, e.g., if the remote file       name is too long.  An example of using the "get" command       to rename a file when transferring it might be "get       really-long-named-file.txt short.txt".     - You may set BINARY mode to transfer executable programs or files       of data.  Type "binary" to do so.  Usually       FTP programs assume files use only 7 bits per byte, the norm for       standard ASCII-encoded files.  The BINARY command allows you to       transfer files that use the full 8 bits per byte without error,       but this may have implications on how the file is transferred       to your local system.       If you are not sure what format a file is in, you may need to       transfer it a second time in the other mode (BINARY or ASCII)       if your first guess is wrong.  The extension at the end of the       file name may give you a clue.  File name extensions are       described below.       Because some machines store text files differently than others,       you may have to try your luck if you're not sure what format       a file is in.  A good guess is to try ASCII mode first, if       you have grounds to suspect the file is a text file.  Otherwise,       try BINARY mode.  Try TENEX mode as a last resort.     - You may transfer multiple files at the same time.  To set this       mode, type "mget".  You then supply a file name pattern that       the remote system understands and it tries to transfer each       file in turn.  If your local FTP user agent cannot transform       the remote file names into legal local file names, or if there       are some files that must be transferred in ASCII mode and others       that must be transferred in BINARY mode, you may not be able to       take advantage of this facility.   Full details on the commands and options available are in the FTP   documentation that comes with your system.  You can also type "help"   at the FTP command prompt for a list of command options.   A copy of the UNIX version of the FTP documentation is available from   the online manual.  If your UNIX site has the manuals installed, type   the following at the UNIX prompt:           % man ftpIAFA Working Group                                              [Page 6]

RFC 1635                       How To FTP                       May 1994The Packaging and Naming of Files   Several widely used conventions allow for efficient storage and   transmission of information stored at archive sites.   Information stored on archive sites is often "transformed" in three   common ways.  "Compressing" (reducing the size of) the stored   information makes more space available on the archive, and reduces   the amount of data actually transferred across the network.   "Bundling" several files into one larger file maintains the internal   directory structure of the components, and allows users to transfer   only one larger object rather than several (sometimes hundreds) of   smaller files.   In addition, binary data is often converted into an ASCII format for   transmission, a process referred to in this document as   "transformation".  Traditionally, InternetRFC 822-based electronic   mail and USENET protocols did not allow the transmission of "binary"   (8-bit) data; therefore, files in binary format had to be transformed   into printable 7-bit ASCII before being transmission.   On many systems, various file naming conventions are used to help the   remote user to determine the format of the stored information without   first having to retrieve the files.  Below we list the more common   compression, bundling, and transformation conventions used on the   Internet.  This list is not intended to be exhaustive.  In all cases   public domain or freely-available implementations of the programs   associated with these mechanisms are available on the network.     1) compress/uncompress     Filenames terminating in ".Z" normally signify files that have been     compressed by the standard UNIX Lempel-Ziv "compress" utility.     There is an equivalent program called "uncompress" to reverse the     process and return the file to its original state.  No bundling     mechanism is provided, and the resulting files are always in binary     format, regardless of the original format of the input data.     2) atob/btoa     Performs a transformation of ASCII to binary (atob) and the reverse     (btoa) in a standard format.  Files so transformed often have     filenames terminated with ".atob".  No bundling or compression     mechanisms are used.IAFA Working Group                                              [Page 7]

RFC 1635                       How To FTP                       May 1994     3) atox/xtoa     A data transformation standard used to convert binary     files to transferable ASCII format.  Sometimes used in     preference to other similar mechanisms because it is more     space efficient; however, it is not a compression     mechanism per se.  It is just more efficient in the     transformation from one format to the other.  Filenames of     files in this format often have the ".atox" extension.     4) uuencode/uudecode     Transforms binary to ASCII ("uuencode") and the reverse     ("uudecode") transformation in a standard manner.     Originally used in the UUCP ("Unix to Unix CoPy")     mail/USENET system.  No bundling or compression mechanisms     are used.  Naming conventions often add a .uu at the end     of the file name.     5) tar/untar     Originally a UNIX based utility for bundling (and     unbundling) several files and directories into (and from)     a single file (the acronym stands for "Tape ARchive").     Standard format provides no compression mechanism.  The     resulting bundled file is always in binary format     regardless of whether the constituent files are binary or     not.  Naming conventions usually hold that the filename of     a "tarfile" contain the sequence ".tar" or "-tar".     6) zip/unzip     Often used in IBM PC environments, these complementary programs     provide both bundling and compression mechanisms.  The resulting     files are always in binary format.  Files resulting from the "zip"     program are by convention terminated with the ".zip" filename     extension.     7) arc/unarc     Often used in IBM PC environments, these complementary programs     provide both bundling and compression mechanisms.  The resulting     files are always in binary format.  Files stored in this format     often have a ".arc" filename extension.IAFA Working Group                                              [Page 8]

RFC 1635                       How To FTP                       May 1994     8) binhex     Used in the Apple MacIntosh environment, the binhex     process provides bundling as well as binary to ASCII data     transformations.  Files in this format by convention have     a filename extension of ".hqx".     9) shar     Bourse shell archives package text or binary files into a     single longer file which, when executed, will create the     component files.  Because this format is vulnerable to     misuse, most users use a special tool called unshar to     decode these archives.  By convention, files in this     format have a filename extension of ".shar".     10) VMS_SHARE     DCL archives package text or binary files into a single     longer file which, when executed, will created the     component files.  Because this format is vulnerable to     misuse, care must be take to examine such an archive     before executing it.  By convention, files in this format     have a filename extension of ".shar".     11) Multipart shar/vms_share files     Sometimes these shell archive files are broken into     multiple small parts to simplify their transfer over other     forms of fileservers that share the same archive tree.  In     such cases, the parts of the files are usually suffixed     with a part number (e.g., xyz.01 xyz.02 xyz.03 ... or even     .01-of-05).  Collect all the parts, concatenate them on     your local system, and then apply the procedure listed     above for a simple shar or vms_share file to the     concatenated file you just made.     12) zoo     The zoo program implements compression/decompression and     bundling/unbundling in a single program.  Utilities     supporting the zoo format exist on a wide variety of     systems, including Unix, MS-DOS, Macintosh, OS/2, Atari     ST, and VAX VMS.  Files created by the "zoo" programs by     convention end with the ".zoo" filename extension.  Zoo is     a popular distribution format due to the availability of     free implementations (both source and executable code) on     a wide variety of operating systems.IAFA Working Group                                              [Page 9]

RFC 1635                       How To FTP                       May 1994     13) gzip/gunzip     The Free Software Foundation GNU project adopted a variant     of the zip compression mechanism as a substitute for the     compress/uncompress commands.  The resulting files are     always in binary format.  Files resulting from the "gzip"     program are by convention terminated with the ".z" or     ".gz" filename extensions.  The gunzip program also     recognizes ".tgz" and ".taz" as shorthands for ".tar.z" or     ".tar.Z".  Also, gunzip can recognize and decompress files     created by the gzip, zip, compress, or pack commands.     The GNU project recently began distributing and using the     gzip/gunzip utilities.  Even more recently they changed     the default suffix from .z to .gz, in an attempt to (1)     reduce confusion with .Z, and (2) eliminate a problem with     case-insensitive file systems such as MS-DOS.  The gzip     software is freely redistributable and has been ported to     most UNIX systems, as well as Amiga, Atari, MSDOS, OS2,     and VMS systems.   In some cases, a series of the above processes are performed to   produce the final file as stored on the archive.  In cases where   multiple transformation processes have been used, tradition holds   that the original (base) filename be changed to reflect these   processes, and that the associated filename extensions be added in   the order in which the processes were performed.  For example, a   common procedure is first to bundle the original files and   directories using the "tar" process, then to "compress" the bundled   file.  Starting with a base file name of "foobar", the file name in   the archive would become "foobar.tar.Z".  As this is a binary file,   it would require a further transformation into printable ASCII by a   program such as "uuencode" in order to be transmitted over   traditional email or USENET facilities, so it might finally be called   "foobar.tar.Z.uu."   Some operating systems can not handle multiple periods; in such cases   they are often replaced by hyphen ( - ), underscore ( _ ), or by   detailed instructions in the "read me" files in the directories.Compress and Tar   Here is an example of the use of the "compress/uncompress" and   "tar/untar" programs.   Suppose "patch" is a useful public domain program for applying   program patches and updates.  You find this file at an archive site   as "patch.tar.Z".  Now you know that the ".Z" indicates that the fileIAFA Working Group                                             [Page 10]

RFC 1635                       How To FTP                       May 1994   was compressed with the UNIX "compress" command, and the ".tar"   indicates that it was tar'ed using the UNIX "tar" tape archive   command.   First retrieve the file onto your machine using anonymous FTP.  To   unpack this program, you would first  uncompress it by typing:      uncompress patch.tar.Z   This will uncompress the file, and in the process, rename it to   "patch.tar".  You can then execute the "tar" command to extract the   individual files.   In the example of patch.tar, you could invoke the command as:      %tar xvf patch.tar   The files would be extracted (that's the 'x' argument to tar) from   the file patch.tar (that's the 'f' argument).  Because we use the 'v'   (for verbose) argument, the name of each file is printed as it is   extracted.  When tar is complete you should have all the files that   make up the "patch" program in your working directory.Etiquette   Not every site that supports FTP permits anonymous tranfers.  It is   wrong to try to get files from systems that have not advertised the   availability of such a service.   Remember that Internet site administrators for archive sites have   made their systems available out of a sense of community.  Rarely are   they fully compensated for the time and effort it takes to administer   such a site.  There are some things users can do to make their jobs   somewhat easier, such as checking with local support personnel first   if problems occur before asking the archive administrator for help.   Most archive machines perform other functions as well.  Please   respect the needs of their primary users and restrict your FTP access   to non-prime hours (generally between 1900 and 0600 hours local time   for that site) whenever possible.  It is especially important to   remember this for sites located on another continent or across a   significant body of water because most such links are relatively slow   and heavily loaded.IAFA Working Group                                             [Page 11]

RFC 1635                       How To FTP                       May 1994   In addition, some sites offering anonymous FTP limit the number of   concurrent anonymous FTP logins.  If your attempt to log onto such a   site results in an error message to the effect that too many   anonymous FTP users are online, you should wait a while before   attempting another connection rather than retrying immediately.   To reduce redundant storage, you should find out how to make useful   the files you fetch using FTP available to your entire organization.   If you retrieve and test a program that turns out to be useful, you   should probably ask your administrator to consider making the program   generally available, which will reduce the redundant effort and disk   space resulting from multiple individuals installing the same package   in their personal directories.   If you find an interesting file or program on an archive site, tell   others about it.  You should not copy the file or program to your own   archive unless you are willing to keep your copy current.References   [1] Postel, J., and J. Reynolds, "File Transfer Protocol (FTP)", STD       9,RFC 959, USC/Information Sciences Institute, October 1985.Security Considerations   Security issues are not discussed in this memo.IAFA Working Group                                             [Page 12]

RFC 1635                       How To FTP                       May 1994Authors' Addresses   Peter Deutsch   Bunyip Information Systems   266 Blvd. Neptune   Dorval, Quebec, H9S 2L4   Canada   Phone: (514) 398-3709   EMail: peterd@bunyip.com   Alan Emtage   Bunyip Information Systems   266 Blvd. Neptune   Dorval, Quebec, H9S 2L4   Canada   Phone: (514) 398-3709   EMail: bajan@bunyip.com   April N. Marine   NASA NAIC   M/S 204-14   Ames Research Center   Moffett Field, CA 94035-1000   Phone: (415) 604-0762   EMail: amarine@atlas.arc.nasa.govIAFA Working Group                                             [Page 13]