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rfc:fyi:fyi24

Network Working Group P. Deutsch Request for Comments: 1635 A. Emtage FYI: 24 Bunyip Category: Informational A. Marine

                                                             NASA NAIC
                                                              May 1994
                      How to Use Anonymous FTP

Status 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 other

IAFA 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
     for RFC 959 on this host is files/rfc/rfc959.txt.  In the

IAFA 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.rfc
 250-  it was last modified on Fri Jul 30 16:47:29 1993 - 298 days ago
 250 CWD command successful.
 ftp> get rfc959.txt
 200 PORT command successful.
 150 Opening ASCII mode data connection for rfc959.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 1994

Variations

 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:
  1. Log in to your local host, and invoke the FTP program.
  1. Open a connection to the host (using either the host name

or its IP address)

  1. Once connected to the remote host, log in with username

"anonymous".

  1. Provide either the password "guest" or whatever the password the

site requests.

  1. Issue whatever FTP commands you require, such as those to

change directories or to retrieve a file.

  1. 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:
  1. You may ask the FTP program to display a list of available

commands, typically by invoking the FTP program without

     arguments and typing "help".
  1. You may view the contents of the directory to which you are

connected. Type "dir" or "ls" to do so.

  1. You may rename a file by using the "get" command's

optional local file name, which follows the remote file

IAFA 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".
  1. 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.
  1. 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 ftp

IAFA Working Group [Page 6] RFC 1635 How To FTP May 1994

The 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, Internet RFC 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 file

IAFA 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 1994

Authors' 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.gov

IAFA Working Group [Page 13]

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