TFTPD(8) BSD System Manager's Manual TFTPD(8)
tftpd -- DARPA Internet Trivial File Transfer Protocol server
tftpd [-cdln] [-g group] [-p pathsep] [-s directory] [-u user] [directory ...]
tftpd is a server which supports the DARPA Trivial File Transfer Protocol. The TFTP server
operates at the port indicated 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. Filenames beginning in ``../'' or containing ``/../'' are not allowed. Unless -c
is used, files may be written to 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 implica-
tions 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 directories by including
up to 20 pathnames as server program arguments in /etc/inetd.conf. 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 options are:
-c Allow unrestricted creation of new files. Without this flag, only existing
publicly writable files can be overwritten.
-d Enable verbose debugging messages to syslogd(8).
-g group Change gid to that of group on startup. If this isn't specified, the gid is
set to that of the user specified with -u.
-l Logs all requests using syslog(3).
-n Suppresses negative acknowledgement of requests for nonexistent relative
-p pathsep All occurances of the single character pathsep (path separator) in the
requested filename are replaced with '/'.
-s directory tftpd will chroot(2) to directory on startup. This is recommended for secu-
rity reasons (so that files other than those in the /tftpboot directory
aren't accessible). If the remote host passes the directory name as part of
the file name to transfer, you may have to create a symbolic link from
'tftpboot' to '.' under /tftpboot.
-u user Change uid to that of user on startup. If -u isn't given, user defaults to
``nobody''. If -g isn't also given, change the gid to that of user as well.
The TFTP Protocol (Revision 2), RFC, 1350, July 1992.
TFTP Option Extension, RFC, 2347, May 1998.
TFTP Blocksize Option, RFC, 2348, May 1998.
TFTP Timeout Interval and Transfer Size Options, RFC, 2349, May 1998.
The tftpd command appeared in 4.2BSD.
The -s flag appeared in NetBSD 1.0.
The -g and -u flags appeared in NetBSD 1.4.
IPv6 support was implemented by WIDE/KAME project in 1999.
TFTP options were implemented by Wasabi Systems, Inc., in 2003, and first appeared in
Files larger than 33,553,919 octets (65535 blocks, last one less than 512 octets) cannot be
correctly transferred without client and server supporting blocksize negotiation (RFCs 2347
and 2348). As a kludge, tftpd accepts a sequence of block numbers which wrap to zero after
Many tftp clients will not transfer files over 16,776,703 octets (32767 blocks), as they
incorrectly count the block number using a signed rather than unsigned 16-bit integer.
You are strongly advised to set up tftpd using the -s flag in conjunction with the name of
the directory that contains the files that tftpd will serve to remote hosts (e.g.,
/tftpboot). This ensures that only the files that should be served to remote hosts can be
accessed by them.
Because there is no user-login or validation within the TFTP protocol, the remote site will
probably have some sort of file-access restrictions in place. The exact methods are spe-
cific to each site and therefore difficult to document here.
If unrestricted file upload is enabled via the -c option, care should be taken that this can
be used to fill up disk space in an uncontrolled manner if this is used in an insecure envi-
BSD April 22, 2010 BSD