tftpd man page on FreeBSD

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TFTPD(8)		  BSD System Manager's Manual		      TFTPD(8)

NAME
     tftpd — Internet Trivial File Transfer Protocol server

SYNOPSIS
     tftpd [-cdClnow] [-F strftime-format] [-s directory] [-u user] [-U umask]
	   [directory ...]

DESCRIPTION
     The tftpd utility is a server which supports the Internet Trivial File
     Transfer Protocol (RFC 1350).  The TFTP server operates at the port indi‐
     cated in the ‘tftp’ service description; see services(5).	The server is
     normally started by inetd(8).

     The use of tftp(1) does not require an account or password on the remote
     system.  Due to the lack of authentication information, tftpd will allow
     only publicly readable files to be accessed.  Files containing the string
     “/../” or starting with “../” are not allowed.  Files may be written only
     if they already exist and are publicly writable.  Note that this extends
     the concept of “public” to include all users on all hosts that can be
     reached through the network; this may not be appropriate on all systems,
     and its implications should be considered before enabling tftp service.
     The server should have the user ID with the lowest possible privilege.

     Access to files may be restricted by invoking tftpd with a list of direc‐
     tories by including up to 20 pathnames as server program arguments in
     inetd.conf(5).  In this case access is restricted to files whose names
     are prefixed by the one of the given directories.	The given directories
     are also treated as a search path for relative filename requests.

     The -s option provides additional security by changing the root directory
     of tftpd, thereby prohibiting accesses to outside of the specified
     directory.	 Because chroot(2) requires super-user privileges, tftpd must
     be run as root.  However, after performing the chroot(2) call, tftpd will
     set its user ID to that of the specified user, or “nobody” if no -u
     option is specified.

     The options are:

     -c	     Changes the default root directory of a connecting host via
	     chroot(2) based on the connecting IP address.  This prevents mul‐
	     tiple clients from writing to the same file at the same time.  If
	     the directory does not exist, the client connection is refused.
	     The -s option is required for -c and the specified directory is
	     used as a base.

     -C	     Operates the same as -c except it falls back to directory speci‐
	     fied via -s if a directory does not exist for the client's IP.

     -F	     Use this strftime(3) compatible format string for the creation of
	     the suffix if -W is specified.  By default the string "%Y%m%d" is
	     used.

     -d	     Enables debug output.  If specified twice, it will log DATA and
	     ACK packets too.

     -l	     Log all requests using syslog(3) with the facility of LOG_FTP.
	     Note: Logging of LOG_FTP messages must also be enabled in the
	     syslog configuration file, syslog.conf(5).

     -n	     Suppress negative acknowledgement of requests for nonexistent
	     relative filenames.

     -o	     Disable support for RFC2347 style TFTP Options.

     -s directory
	     Cause tftpd to change its root directory to directory.  After
	     doing that but before accepting commands, tftpd will switch cre‐
	     dentials to an unprivileged user.

     -u user
	     Switch credentials to user (default “nobody”) when the -s option
	     is used.  The user must be specified by name, not a numeric UID.

     -U umask
	     Set the umask for newly created files.  The default is 022
	     (S_IWGRP | S_IWOTH).

     -w	     Allow write requests to create new files.	By default tftpd
	     requires that the file specified in a write request exist.	 Note
	     that this only works in directories writable by the user speci‐
	     fied with -u option

     -W	     As -w but append a YYYYMMDD.nn sequence number to the end of the
	     filename.	Note that the string YYYYMMDD can be changed with the
	     -F option.

SEE ALSO
     tftp(1), chroot(2), syslog(3), inetd.conf(5), services(5),
     syslog.conf(5), inetd(8)

     K. R. Sollins, The TFTP Protocol (Revision 2), July 1992, RFC 1350, STD
     33.

HISTORY
     The tftpd utility appeared in 4.2BSD; the -s option was introduced in
     FreeBSD 2.2, the -u option was introduced in FreeBSD 4.2, the -c option
     was introduced in FreeBSD 4.3, and the -F and -W options were introduced
     in FreeBSD 7.4.

     Support for Timeout Interval and Transfer Size Options (RFC2349) was
     introduced in FreeBSD 5.0, support for the TFTP Blocksize Option
     (RFC2348) and the blksize2 option was introduced in FreeBSD 7.4.

BUGS
     Files larger than 33488896 octets (65535 blocks) cannot be transferred
     without client and server supporting blocksize negotiation (RFC2348).

     Many tftp clients will not transfer files over 16744448 octets (32767
     blocks).

BSD			      September 14, 2000			   BSD
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