NAME¶
ftpd —
Internet File Transfer Protocol
server
SYNOPSIS¶
ftpd |
[-dlADq]
[-T
maxtimeout]
[-t
timeout]
[-a
login-name] |
DESCRIPTION¶
Ftpd is the 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).
Available options:
- -d
- Debugging information is written to the syslog using
LOG_FTP.
- -l
- 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.
- -A
- Only anonymous login is allowed.
- -D
- ftpd enters daemon-mode. That allows ftpd to be run without
inetd.
- -q
- Quiet mode. No information about the version of the ftpd is
given to the client.
- -T
- 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
- The inactivity timeout period is set to
timeout seconds (the default is 15 minutes).
- -a
- Give anonymous an other login-name
(anonymous and ftpd will still work).
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 CHMOD 755
filename'' |
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 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 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.
- 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 performed.
- The login name must not appear in the file
/etc/ftpusers.
- The user must have a standard shell returned by
getusershell(3).
- 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.
FILES¶
- /etc/ftpusers
- List of unwelcome/restricted users.
- /etc/ftpwelcome
- Welcome notice.
- /etc/motd
- Welcome notice after login.
- /etc/nologin
- Displayed and access refused.
SEE ALSO¶
ftp(1),
getusershell(3),
syslogd(8)
BUGS¶
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.
HISTORY¶
The
ftpd command appeared in
4.2BSD.