FTPD
Section: Maintenance Commands (8)
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BSD mandoc
Linux NetKit (0.17)
NAME
ftpd
- Internet File Transfer Protocol server
SYNOPSIS
ftpd
[-AdDhlMnPSU
]
[-T maxtimeout
]
[-t timeout
]
[-u mask
]
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:
- -4
-
Use IPv4 addressing only. The default is to offer service for both families, IPv6 and IPv4.
- -6
-
Only provide IPv6 addressing capability.
- -A
-
Permit only anonymous ftp connections or accounts listed in
/etc/ftpchroot.
Other connection attempts are refused. This option is no longer effective if
PAM is enabled. Please refer to the README file for instructions to doing
this with PAM.
- -d
-
Debugging information is written to the syslog using LOG_FTP.
- -D
-
With this option set,
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
-
The server will use data ports in the high port range for passive connections.
This range is defined by the
IPPORT_HIFIRSTAUTO
and
IPPORT_HILASTAUTO
defines in <netinet/in.h>. In
Ox they are set to 49152 and 65535 respectively.
- -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.
- -M
-
Enables multihomed mode. Instead of simply using
~ftp
for anonymous transfers, a directory matching the fully qualified name of
the IP number the client connected to, and located inside
~ftp
is used instead.
- -n
-
Use numeric IP addresses in logs instead of doing hostname lookup.
- -P
-
Permit illegal port numbers or addresses for PORT command initiated connects.
By default
ftpd(8)
violates the RFC and thus constrains the PORT command to non-reserved ports
and requires it use the same source address as the connection came from.
This prevents the "FTP bounce attack" against services on both the local
machine and other local machines.
- -S
-
With this option set,
ftpd
logs all anonymous transfers to the file
/var/log/ftpd
when this file exists.
- -U
-
Each concurrent
ftp(1)
session is logged to the file
/var/run/utmp
making them visible to commands such as
who(1).
This option at present is unsupporte and will always silently fail.
- -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).
- -u
-
Change the default umask from 027 to
mask
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 Ta Description
-
- ABOR Ta abort previous command
-
- ACCT Ta specify account (ignored)
-
- ALLO Ta allocate storage (vacuously)
-
- APPE Ta append to a file
-
- CDUP Ta change to parent of current working directory
-
- CWD Ta change working directory
-
- DELE Ta delete a file
-
- EPRT Ta specify data connection port, either IPv4 or IPv6
-
- EPSV Ta ask for a server port for fetching data
-
- HELP Ta give help information
-
- LIST Ta give list files in a directory (``ls -lgA
''
)
-
- MKD Ta make a directory
-
- MDTM Ta show last modification time of file
-
- MODE Ta specify data transfer mode
-
- NLST Ta give name list of files in directory
-
- NOOP Ta do nothing
-
- PASS Ta specify password
-
- PASV Ta prepare for server-to-server transfer
-
- PORT Ta specify data connection port
-
- PWD Ta print the current working directory
-
- QUIT Ta terminate session
-
- REST Ta restart incomplete transfer
-
- RETR Ta retrieve a file
-
- RMD Ta remove a directory
-
- RNFR Ta specify rename-from file name
-
- RNTO Ta specify rename-to file name
-
- SITE Ta non-standard commands (see next section)
-
- SIZE Ta return size of file
-
- STAT Ta return status of server
-
- STOR Ta store a file
-
- STOU Ta store a file with a unique name
-
- STRU Ta specify data transfer structure
-
- SYST Ta show operating system type of server system
-
- TYPE Ta specify data transfer type
-
- USER Ta specify user name
-
- XCUP Ta change to parent of current working directory (deprecated)
-
- XCWD Ta change working directory (deprecated)
-
- XMKD Ta make a directory (deprecated)
-
- XPWD Ta print the current working directory (deprecated)
-
- XRMD Ta remove a directory (deprecated)
-
The following non-standard or
UNIX
specific commands are supported
by the
SITE request.
- Request Ta Description
-
- UMASK Ta change umask, e.g. ``SITE UMASK 002''
-
- IDLE Ta set idle-timer, e.g. ``SITE IDLE 60''
-
- CHMOD Ta change mode of a file, e.g. ``SITE CHMOD 755 filename''
-
- HELP Ta 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.
-
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.
If the user has an S/Key key, the response from a successful USER
command will include an S/Key challenge. The client may choose to respond
with a PASS command giving either a standard password or an S/Key
one-time password. The server will automatically determine which type of
password it has been given and attempt to authenticate accordingly. See
skey(1)
for more information on S/Key authentication. S/Key is a Trademark of
Bellcore.
-
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 appears in the file
/etc/ftpchroot
the session's root will be changed to the user's login directory by
chroot(2)
as for an
``anonymous''
or
``ftp''
account (see next item). However, the user must still supply a password.
This feature is intended as a compromise between a fully anonymous account
and a fully privileged account. The account should also be set up as for an
anonymous account.
-
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 (mode 555).
- ~ftp/bin
-
Make this directory owned by
``root''
and unwritable by anyone (mode 511).
This directory is required, and should contain at least a statically
linked copy of
ls(1).
Any programs in this directory should be mode 111 (executable only).
- ~ftp/etc
-
Make this directory owned by
``root''
and unwritable by anyone (mode 511).
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/lib
-
Make this directory owned by
``root''
and unwritable by anyone (mode 511).
The libraries
ld-linux.so.2
and
libc.so.6
(or whatever your
ls
command is linked to)
must be present.
In order to read
passwd(5)
and
group(5),
the library
libnss_files.so.2
is also needed.
Note that if you're using a 2.2.* or later Linux kernel,
ld-linux.so.2
must be executable as well as readable (555). All other files should be mode
444.
- ~ftp/pub
-
Make this directory mode 555 and owned by
``root''
This is traditionally where publically accessible files are
stored for download.
FILES
- /etc/ftpusers
-
List of unwelcome/restricted users.
- /etc/ftpchroot
-
List of normal users who should be chroot'd.
- /etc/ftpwelcome
-
Welcome notice.
- /etc/motd
-
Welcome notice after login.
- /etc/nologin
-
Displayed and access refused.
- /var/run/utmp
-
List of users on the system.
- /var/log/ftpd
-
Log file for anonymous transfers.
SEE ALSO
ftp(1),
skey(1),
who(1),
getusershell(3),
ftpusers(5),
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
BSD 4.2
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- FILES
-
- SEE ALSO
-
- BUGS
-
- HISTORY
-
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Time: 19:49:30 GMT, April 27, 2011