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GNU networking utilities

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3.1 Invoking

The options are as follows:

`-A'
`--anonymous-only'
Only anonymous login is allowed.

`-a AUTH'
`--auth=AUTH'
Give anonymous an other login-name (anonymous and ftpd will still work).

`-D'
`--daemon'
ftpd enters daemon-mode. That allows ftpd to be run without inetd.

`-d'
`--debug'
Debugging information is written to the syslog using LOG_FTP.

`-l'
`--logging'
Each successful and failed ftp(1) session is logged using syslog with a facility of LOG_FTP. If this option is specified twice, the retrieve (get), store (put), append, delete, make directory, remove directory and rename operations and their filename arguments are also logged.

`-p PIDFILE'
`--pidfile=PIDFILE'
Change default location of PIDFILE

`-q'
`--no-version'
Quiet mode. No information about the version of the ftpd is given to the client.

`-T'
`--max-timeout'
A client may also request a different timeout period; the maximum period allowed may be set to timeout seconds with the -T option. The default limit is 2 hours.

`-t TIMEOUT'
`--timeout=TIMEOUT'
The inactivity timeout period is set to timeout seconds (the default is 15 minutes).

`-u UMASK'
`--umask=UMASK'
Set default umask(base 8).

The file `/etc/nologin' can be used to disable ftp access. If the file exists, ftpd displays it and exits. If the file `/etc/ftpwelcome' exists, ftpd prints it before issuing the "ready" message. If the file /etc/motd exists, ftpd prints it after a successful login.

The ftp server currently supports the following ftp requests. The case of the requests is ignored.

 
           Request    Description
           ABOR       abort previous command
           ACCT       specify account (ignored)
           ALLO       allocate storage (vacuously)
           APPE       append to a file
           CDUP       change to parent of current working directory
           CWD        change working directory
           DELE       delete a file
           HELP       give help information
           LIST       give list files in a directory (``ls -lgA'')
           MKD        make a directory
           MDTM       show last modification time of file
           MODE       specify data transfer mode
           NLST       give name list of files in directory
           NOOP       do nothing
           PASS       specify password
           PASV       prepare for server-to-server transfer
           PORT       specify data connection port
           PWD        print the current working directory
           QUIT       terminate session
           REST       restart incomplete transfer
           RETR       retrieve a file
           RMD        remove a directory
           RNFR       specify rename-from file name
           RNTO       specify rename-to file name
           SITE       non-standard commands (see next section)
           SIZE       return size of file
           STAT       return status of server
           STOR       store a file
           STOU       store a file with a unique name
           STRU       specify data transfer structure
           SYST       show operating system type of server system
           TYPE       specify data transfer type
           USER       specify user name
           XCUP       change to parent of current working directory
                      (deprecated)
           XCWD       change working directory (deprecated)
           XMKD       make a directory (deprecated)
           XPWD       print the current working directory (deprecated)
           XRMD       remove a directory (deprecated)

     The following non-standard or UNIX specific commands are supported by the
     SITE request.

           Request    Description
           UMASK      change umask, e.g. ``SITE UMASK 002''
           IDLE       set idle-timer, e.g. ``SITE IDLE 60''
           CHMOD      change mode of a file, e.g. ``SITE CHMOD0 0CHMOD1
                      1CHMOD2
           HELP       give help information.


The remaining ftp requests specified in Internet RFC 959 are recognized, but not implemented. MDTM and SIZE are not specified in RFC 959, but will appear in the next updated FTP RFC.

The ftp server will abort an active file transfer only when the ABOR com- mand is preceded by a Telnet "Interrupt Process" (IP) signal and a Telnet Synch" signal in the command Telnet stream, as described in Internet RFC 959. If a STAT command is received during a data transfer, preceded by a Telnet IP and Synch, transfer status will be returned.

Ftpd interprets file names according to the "globbing" conventions used by csh(1). This allows users to utilize the metacharacters "*?[]{}~".

Ftpd authenticates users according to three rules.

  1. The login name must be in the password data base, `/etc/passwd', and not have a null password. In this case a password must be provided by the client before any file operations may be per- formed.

  2. The login name must not appear in the file `/etc/ftpusers'.

  3. The user must have a standard shell returned by getusershell(3).

  4. If the user name is "anonymous" or "ftp", an anonymous ftp account must be present in the password file (user "ftp"). In this case the user is allowed to log in by specifying any password (by convention an email address for the user should be used as the password).

In the last case, ftpd takes special measures to restrict the client's access privileges. The server performs a chroot(2) to the home directory of the "ftp" user. In order that system security is not breached, it is recommended that the "ftp" subtree be constructed with care, following these rules:

`~ftp'
Make the home directory owned by "root" and unwritable by anyone.

`~ftp/bin'
Make this directory owned by "root" and unwritable by anyone (mode 555). The program ls(1) must be present to support the list command. This program should be mode 111.

`~ftp/etc'
Make this directory owned by "root" and unwritable by anyone (mode 555). The files passwd(5) and group(5) must be present for the ls command to be able to produce owner names rather than numbers. The password field in passwd is not used, and should not contain real passwords. The file motd, if present, will be printed after a successful login. These files should be mode 444.

`~ftp/pub'
Make this directory mode 777 and owned by "ftp". Guests can then place files which are to be accessible via the anonymous account in this directory.


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