ftpd
FTPD(8) FTPD(8)
NAME
ftpd - Internet File Transfer Protocol server
SYNOPSIS
ftpd [ -d ] [ -v ] [ -l ] [ -t timeout ] [ -T maxtimeout ]
[ -a ] [ -A ] [ -L ] [ -i ] [ -I ] [ -o ] [ -p ctrlport ]
[ -P dataport ] [ -q ] [ -Q ] [ -r rootdir ] [ -s ] [ -S ]
[ -u umask ] [ -V ] [ -w ] [ -W ] [ -X ]
DESCRIPTION
Ftpd is the Internet File Transfer Protocol server pro
cess. The server uses the TCP protocol and listens at the
port specified in the ``ftp'' service specification; see
services(5).
version information, then terminate.
If the -d or -v option is specified, debugging information
is written to the syslog.
If the -l option is specified, each ftp session is logged
in the syslog.
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.
If the -a option is specified, the use of the ftpaccess(5)
configuration file is enabled.
If the -A option is specified, use of the ftpaccess(5)
configuration file is disabled. This is the default.
If the -L option is specified, commands sent to the
ftpd(8) server will be logged to the syslog. The -L
option is overridden by the use of the ftpaccess(5) file.
If the -L flag is used, command logging will be on by
default as soon as the ftp server is invoked. This will
cause the server to log all USER commands, which if a user
accidentally enters a password for that command instead of
the username, will cause passwords to be logged via sys
log.
If the -i option is specified, files received by the
ftpd(8) server will be logged to the xferlog(5). The -i
option is overridden by the use of the ftpaccess(5) file.
The -I option disables the use of RFC931 (AUTH/ident) to
attempt to determine the username on the client.
If the -o option is specified, files transmitted by the
ftpd(8) server will be logged to the xferlog(5). The -o
option is overridden by the use of the ftpaccess(5) file.
If the -X option is specified, the output created by the
-i and -o options is not saved to the xferlog file but
saved via syslog so you can collect output from several
hosts on one central loghost.
If the -u option is specified, the default umask is set to
umask.
If the -W option is specified user logins are not recorded
in the wtmp file. The default ( -w ) is to record every
login and logout.
The -s and -S options place the daemon in standalone oper
ation mode. The -S option runs the daemon in the back
ground and is useful in startup scripts during system ini
tialization (ie., in rc.local). The -s option leaves the
daemon in foreground and is useful when running from init
(ie., /etc/inittab).
The -p and -P options override the port numbers used by
the daemon. Normally, the daemon determines the port num
bers by looking in /etc/services for "ftp" and "ftp-data".
If there is no /etc/services entry for "ftp-data" and the
-P option is not specified, the daemon uses the port just
prior to the control connection port. The -p option is
only available if running as a standalone daemon.
The -q and -Q options deterine whether the daemon uses the
PID files. These files are required by the limit direc
tive to determine the number of current users in each
access class. Disabling the use of the PID files disables
user limits. The default ( -q ) is to use the PID files.
Specify -Q when testing the server as a normal user when
access permissions prevent the use of the PID files.
Large, busy sites which do not wish to impose limits on
the number of concurrent users may also consider disabling
the PID files.
The -r option instructs the daemon to chroot(2) to the
specified rootdir immedeately upon loading. This can
improve system security by limiting the files which may be
damaged should a breakin occur through the daemon. Set is
much like anonymous FTP, with additional files needed
which vary from system to system.
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
NEWER list files newer than a particular date
MINFO like SITE NEWER, but gives extra information
GROUP request special group access. E.g. SITE GROUP foo
GPASS give special group access password. E.g. SITE GPASS bar
EXEC execute a program. E.g. SITE EXEC program params
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, pre
ceded 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 four rules.
1) The user name must be in the password data base,
/etc/passwd, or whatever is appropriate for the
operating system, and the password must not be
null. 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 pass
word file (user ``ftp''). In this case the user is
allowed to log in by specifying any password (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 super-user and
unwritable by anyone.
~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.
Depending on the operating system, there may be
other required files. Check your manual page for
the getpwent(3) library routine. The password
field in passwd is not used, and should not contain
real encrypted passwords. These files should be
mode 444 and owned by the super-user. Don't use
the system's /etc/passwd file as the password file
or the system's /etc/group file as the group file
in the ~ftp/etc directory.
~ftp/pub)
Create a subdirectory in ~ftp/pub with the appro
priate mode (777 or 733) if you want to allow nor
mal users to upload files.
AUTHENTICATION MECHANISM ON BSD/OS SYSTEMS ONLY
The authentication mechanism used by ftpd is determined by
the ``auth-ftp'' entry in the /etc/login.conf file (see
login.conf(5)) that matches the users class. If there is
no ``auth-ftp'' entry for the class, the normal ``auth''
entry will be used instead. An alternate authentication
mechanism may be specified by appending a colon (``:'')
followed by the authentication style, i.e. ``joe:skey''.
GENERAL FTP EXTENSIONS
There are some extensions to the FTP server such that if
the user specifies a filename (when using a RETRIEVE com
mand) such that:
True Filename Specified Filename Action
------------- ------------------ -----------------------------------
<filename>.Z <filename> Decompress file before transmitting
<filename> <filename>.Z Compress <filename> before
transmitting
<filename> <filename>.tar Tar <filename> before transmitting
<filename> <filename>.tar.Z Tar and compress <filename> before
transmitting
Also, the FTP server will attempt to check for valid e-
mail addresses and chide the user if he doesn't pass the
test. For users whose FTP client will hang on "long
replies" (i.e. multiline responses), using a dash as the
first character of the password will disable the server's
lreply() function.
The FTP server can also log all file transmission and
reception, keeping the following information for each file
transmission that takes place.
Mon Dec 3 18:52:41 1990 1 wuarchive.wustl.edu 568881 /files.lst.Z a _ o a chris@wugate.wustl.edu ftp 0 *
%.24s %d %s %d %s %c %s %c %c %s %s %d %s
1 2 3 4 5 6 7 8 9 10 11 12 13
1 current time in the form DDD MMM dd hh:mm:ss YYYY
2 transfer time in seconds
3 remote host name
4 file size in bytes
5 name of file
6 transfer type (a>scii, b>inary)
7 special action flags (concatenated as needed):
C file was compressed
U file was uncompressed
T file was tar'ed
_ no action taken
8 file was sent to user (o>utgoing) or received from
user (i>ncoming)
9 accessed anonymously (r>eal, a>nonymous, g>uest) -- mostly for FTP
10 local username or, if guest, ID string given
(anonymous FTP password)
11 service name ('ftp', other)
12 authentication method (bitmask)
0 none
1 RFC931 Authentication
13 authenticated user id (if available, '*' otherwise)
SEE ALSO
ftp(1), getusershell(3), syslogd(8), ftpaccess(5), xfer
log(5), umask(2)
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.
Jan 10, 1997 FTPD(8)