TFTPD(8) BSD System Manager's Manual TFTPD(8)NAMEtftpd — DARPA Internet Trivial File Transfer Protocol server
SYNOPSIStftpd [-d] [-g group] [-i] [-l] [-n] [-s directory] [-u user]
[directory ...]
DESCRIPTIONtftpd is a server which supports the DARPA Trivial File Transfer Proto‐
col. The TFTP server operates at the port indicated in the ‘tftp’ ser‐
vice description; see services(5). This server should not be started
manually; instead, it should be run using launchd(8) using the plist
/System/Library/LaunchDaemons/tftp.plist. It may be started using the
launchctl(1) load command; refer to the documentation for that utility
for more information.
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. 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 appro‐
priate on all systems, and its implications should be considered before
enabling tftp service. The server should have the user ID with the low‐
est 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
/System/Library/LaunchDaemons/tftp.plist. 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:
-d Enable verbose debugging messages to syslogd(8).
-g group Change gid to that of group on startup. If this isn't speci‐
fied, the gid is set to that of the user specified with -u.
-i Enable insecure mode, no realpath(3).
-l Logs all requests using syslog(3).
-n Suppresses negative acknowledgement of requests for nonexis‐
tent relative filenames.
-s directory
tftpd will chroot(2) to directory on startup. This is recom‐
mended for security 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.
SEE ALSOtftp(1), launchd(8), launchctl(1), launchd.plist(5)
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.
HISTORY
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 NetBSD 2.0 .
BUGS
Files larger than 33488896 octets (65535 blocks) cannot be transferred
without client and server supporting blocksize negotiation (RFCs 2347 and
2348).
Many tftp clients will not transfer files over 16744448 octets (32767
blocks).
SECURITY CONSIDERATIONS
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 specific to each site and therefore dif‐
ficult to document here.
BSD June 11, 2003 BSD
