FTPD(8) | System Manager's Manual | FTPD(8) |
ftpd
— Internet
File Transfer Protocol server
ftpd |
[-AdDhlMnPSU ] [-T
maxtimeout] [-t
timeout] [-u
mask] |
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:
-4
-6
-A
-d
-D
ftpd
will detach and become
a daemon, accepting connections on the FTP port and forking child
processes to handle them. This has lower overhead than starting
ftpd
from inetd(8) and is thus
useful on busy servers to reduce load.-h
IPPORT_HIFIRSTAUTO
and
IPPORT_HILASTAUTO
defines in <netinet/in.h>.
In OpenBSD they are set to 49152 and 65535
respectively.-l
-M
-n
-P
-S
ftpd
logs all anonymous
transfers to the file /var/log/ftpd when this file
exists.-U
-T
-T
option. The default limit is 2 hours.-t
-u
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. If
the file .message exists in a directory,
ftpd
prints it when that directory is entered.
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 | specify data connection port, either IPv4 or IPv6 |
EPSV | ask for a server port for fetching data |
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 five
rules.
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(1), skey(1), who(1), getusershell(3), ftpusers(5), syslogd(8)
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.
The ftpd
command appeared in
4.2BSD.
September 14, 1999 | Linux NetKit (0.17) |