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NetBSD 6.1.5 - man page for tftpd (netbsd section 8)

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

NAME
     tftpd -- DARPA Internet Trivial File Transfer Protocol server

SYNOPSIS
     tftpd [-cdln] [-g group] [-p pathsep] [-s directory] [-u user] [directory ...]

DESCRIPTION
     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
		    filenames.

     -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.

SEE ALSO
     tftp(1), inetd(8)

     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 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
     65535.

     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.

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 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-
     ronment.

BSD					  April 22, 2010				      BSD
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