Ubuntu Manpage: ftpd — Internet File Transfer Protocol server

Provided by: inetutils-ftpd_2.5-3ubuntu4_amd64

NAME

     ftpd — Internet File Transfer Protocol server

SYNOPSIS

     ftpd [option ...]

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).

OPTIONS

-4, --ipv4
Restrict daemon to listen to IPv4 addresses only.

-6, --ipv6
Restrict daemon to listen to IPv6 addresses only.

-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.

-A, --anonymous-only
Only anonymous login is allowed.

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

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

-T, --max-timeout 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
The inactivity timeout period is set to timeout seconds (the default is 15 minutes).

-p, --pidfile pidfile
Change default location of pidfile.

-a, --auth auth
Give anonymous another login-name (anonymous and ftpd will still work). It can be one of

default
Use passwd authentication.

pam Use PAM service 'ftp'.

--non-rfc2577
Neglect RFC 2577 by giving information on missing users.

-u, --umask value
Set default umask to value.

-?, --help
Display a help list.

--usage
Display a short usage message.

-V, --version
Display program version.

OPERATION

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
EPRT extended data connection port, RFC 2428
EPSV extended passive transfer request, RFC 2428
FEAT display command extensions
HELP give help information
LIST give list files in a directory (“ls -lgA”)
LPRT long data connection port, RFC 1639
LPSV long passive transfer request, RFC 1639
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
OPTS option settings
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.

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 performed.

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.

FILES

     /etc/ftpusers    List of unwelcome/restricted users.
     /etc/ftpchroot   List of users to change root to their home directory.
     /etc/ftpwelcome  Welcome notice.
     /etc/motd        Welcome notice after login.
     /etc/nologin     Displayed and access refused.

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.