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 another 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.