tftpd(8) - NetBSD Manual Pages

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


NAME

     tftpd - DARPA Internet Trivial File Transfer Protocol server


SYNOPSIS

     tftpd [-d] [-g group] [-l] [-n] [-s directory] [-u user] [directory ...]


DESCRIPTION

     tftpd 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).  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.  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
     /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:

     -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.

     -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 ALSO

     tftp(1), inetd(8)

     The TFTP Protocol (Revision 2), RFC, 1350, July 1992.


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.


BUGS

     Files larger than 33488896 octets (65535 blocks) cannot be transferred
     without client and server supporting blocksize negotiation (RFC1783).

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


SECURITY CONSIDERATIONS

     You are strongly advised to setup 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.

NetBSD 1.6.2                     July 29, 1998                               2