FTPD(8)FTPD(8)NAMEftpd - DARPA Internet File Transfer Protocol server
SYNOPSISftpd [ -d ] [ -l ] [ -ttimeout ] [ -Tmaxtimeout ]
DESCRIPTION
Ftpd is the DARPA Internet File Transfer Protocol server process. The
server uses the TCP protocol and listens at the port specified in the
``ftp'' service specification; see services(5).
If the -d option is specified, debugging information is written to the
syslog.
If the -l option is specified, each ftp session is logged in the sys‐
log.
The ftp server will timeout an inactive session after 15 minutes. If
the -t option is specified, the inactivity timeout period will be set
to timeout seconds. 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.
The ftp server currently supports the following ftp requests; case is
not distinguished.
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 CHMOD 755 filename
HELP give help information. E.g. SITE HELP
The remaining ftp requests specified in Internet RFC 959 are recog‐
nized, 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
command 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 trans‐
fer, 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 user 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 user 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 pass‐
word (by convention this is given as the client host's name).
In the last case, ftpd takes special measures to restrict the client's
access privileges. The server performs a chroot(2) command 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; the following rules are recommended.
~ftp) Make the home directory owned by ``ftp'' and unwritable by any‐
one.
~ftp/bin)
Make this directory owned by the super-user and unwritable by
anyone. The program ls(1) must be present to support the list
command. This program should have mode 111.
~ftp/etc)
Make this directory owned by the super-user and unwritable by
anyone. 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 encrypted passwords. These files should be
mode 444.
~ftp/pub)
Make this directory mode 777 and owned by ``ftp''. Users should
then place files which are to be accessible via the anonymous
account in this directory.
SEE ALSOftp(1), getusershell(3), syslogd(8)BUGS
The anonymous account is inherently dangerous and should avoided when
possible.
The server must run as the super-user to create sockets with privileged
port numbers. It maintains an effective user id of the logged in user,
reverting to the super-user only when binding addresses to sockets.
The possible security holes have been extensively scrutinized, but are
possibly incomplete.
4.2 Berkeley Distribution February 23, 1989 FTPD(8)
