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



NAME
       tftpd - Trivial File Transfer Protocol server

SYNOPSIS
       in.tftpd [options...]  directory...

DESCRIPTION
       tftpd  is  a server for the Trivial File Transfer Protocol.  The TFTP protocol is extensively used to support remote
       booting of diskless devices.  The server is normally started by inetd, but can also run standalone.

OPTIONS
       --ipv4, -4
              Connect with IPv4 only, even if IPv6 support was compiled in.

       --ipv6, -6
              Connect with IPv6 only, if compiled in.

       -l, --listen
              Run the server in standalone (listen) mode, rather than run from inetd.  In listen mode, the --timeout option
              is ignored, and the --address option can be used to specify a specific local address or port to listen to.

       --foreground, -L
              Similar to --listen but do not detach from the foreground process.  Implies --listen.

       --address [address][:port], -a [address][:port]
              Specify  a  specific address and port to listen to when called with the --listen or --foreground option.  The
              default is to listen to the tftp port specified in /etc/services on all local addresses.

              Please note: Numeric IPv6 adresses must be enclosed in square brackets to avoid ambiguity with  the  optional
              port information.

       --create, -c
              Allow  new files to be created.  By default, tftpd will only allow upload of files that already exist.  Files
              are created with default permissions allowing anyone to read  or  write  them,  unless  the  --permissive  or
              --umask options are specified.

       --secure, -s
              Change  root  directory  on startup.  This means the remote host does not need to pass along the directory as
              part of the transfer, and may add security.  When --secure is specified,  exactly  one  directory  should  be
              specified  on  the command line.  The use of this option is recommended for security as well as compatibility
              with some boot ROMs which cannot be easily made to include a directory name in its request.

       --user username, -u username
              Specify the username which tftpd will run as; the default is "nobody".  The user ID, group ID, and (if possi‐
              ble  on  the platform) the supplementary group IDs will be set to the ones specified in the system permission
              database for this username.

       --umask umask, -U umask
              Sets the umask for newly created files to the specified value.  The default  is  zero  (anyone  can  read  or
              write) if the --permissive option is not specified, or inherited from the invoking process if --permissive is
              specified.

       --permissive, -p
              Perform no additional permissions checks above the normal system-provided access controls for the user speci‐
              fied via the --user option.

       --pidfile pidfile, -P pidfile
              When  run  in standalone mode, write the process ID of the listening server into pidfile.  On normal termina‐
              tion (SIGTERM or SIGINT) the pid file is automatically removed.

       --timeout timeout, -t timeout
              When run from inetd this specifies how long, in seconds, to wait for a second connection  before  terminating
              the  server.   inetd will then respawn the server when another request comes in.  The default is 900 (15 min‐
              utes.)

       --retransmit timeout, -T timeout
              Determine the default timeout, in microseconds, before the first packet is retransmitted.  This can be  modi‐
              fied by the client if the timeout or utimeout option is negotiated.  The default is 1000000 (1 second.)

       --map-file remap-file, -m remap-file
              Specify  the  use  of  filename remapping.  The remap-file is a file containing the remapping rules.  See the
              section on filename remapping below.  This option may not be compiled in, see the output of  in.tftpd  -V  to
              verify whether or not it is available.

       --verbose, -v
              Increase  the  logging  verbosity  of  tftpd.  This flag can be specified multiple times for even higher ver‐
              bosity.

       --verbosity value
              Set the verbosity value to value.

       --refuse tftp-option, -r tftp-option
              Indicate that a specific RFC 2347 TFTP option should never be accepted.

       --blocksize max-block-size, -B max-block-size
              Specifies the maximum permitted block size.  The permitted range for this parameter is  from  512  to  65464.
              Some embedded clients request large block sizes and yet do not handle fragmented packets correctly; for these
              clients, it is recommended to set this value to the smallest MTU on your network minus 32 bytes (20 bytes for
              IP,  8 for UDP, and 4 for TFTP; less if you use IP options on your network.)  For example, on a standard Eth‐
              ernet (MTU 1500) a value of 1468 is reasonable.

       --port-range port:port, -R port:port
              Force the server port number (the Transaction ID) to be in the specified range of port numbers.

       --version, -V
              Print the version number and configuration to standard output, then exit gracefully.

RFC 2347 OPTION NEGOTIATION
       This version of tftpd supports RFC 2347 option negotation.  Currently implemented options are:

       blksize (RFC 2348)
              Set the transfer block size to anything less than or equal to the specified option.  This  version  of  tftpd
              can support any block size up to the theoretical maximum of 65464 bytes.

       blksize2 (nonstandard)
              Set the transfer block size to anything less than or equal to the specified option, but restrict the possible
              responses to powers of 2.  The maximum is 32768 bytes (the largest power of 2 less than or equal to 65464.)

       tsize (RFC 2349)
              Report the size of the file that is about to be transferred.  This version of tftpd only supports  the  tsize
              option for binary (octet) mode transfers.

       timeout (RFC 2349)
              Set the time before the server retransmits a packet, in seconds.

       utimeout (nonstandard)
              Set the time before the server retransmits a packet, in microseconds.

       rollover (nonstandard)
              Set the block number to resume at after a block number rollover.  The default and recommended value is zero.

       The  --refuse  option can be used to disable specific options; this may be necessary to work around bugs in specific
       TFTP client implementations.  For example, some TFTP clients have been found to  request  the  blksize  option,  but
       crash with an error if they actually get the option accepted by the server.

FILENAME REMAPPING
       The  --map-file  option  specifies  a file which contains filename remapping rules.  Each non-comment line (comments
       begin with hash marks, #) contains an operation, specified below; a regex, a regular  expression  in  the  style  of
       egrep; and optionally a replacement pattern.  The operation indicated by operation is performed if the regex matches
       all or part of the filename.  Rules are processed from the top down, and by default, all rules are processed even if
       there is a match.

       The operation can be any combination of the following letters:

       r      Replace  the  substring  matched  by  regex  by the replacement pattern.  The replacement pattern may contain
              escape sequences; see below.

       g      Repeat this rule until it no longer matches.  This is always used with r.

       i      Match the regex case-insensitively.  By default it is case sensitive.

       e      If this rule matches, end rule processing after executing the rule.

       s      If this rule matches, start rule processing over from the very first rule after executing this rule.

       a      If this rule matches, refuse the request and send an access denied error to the client.

       G      This rule applies to GET (RRQ) requests only.

       P      This rule applies to PUT (WRQ) requests only.

       ~      Inverse the sense of this rule, i.e. execute the operation only if the  regex  doesn't  match.   Cannot  used
              together with r.

       The following escape sequences are recognized as part of the replacement pattern:

       \0     The entire string matched by the regex.

       \1 to \9
              The strings matched by each of the first nine parenthesized subexpressions, \( ... \), of the regex pattern.

       \i     The IP address of the requesting host, in dotted-quad notation (e.g. 192.0.2.169).

       \x     The IP address of the requesting host, in hexadecimal notation (e.g. C00002A9).

       \\     Literal backslash.

       \whitespace
              Literal whitespace.

       \#     Literal hash mark.

       \U     Turns all subsequent letters to upper case.

       \L     Turns all subsequent letters to lower case.

       \E     Cancels the effect of \U or \L.

       If the mapping file is changed, you need to send SIGHUP to any outstanding tftpd process.

SECURITY
       The use of TFTP services does not require an account or password on the server system.  Due to the lack of authenti‐
       cation information, tftpd will allow only publicly readable files (o+r) to  be  accessed,  unless  the  --permissive
       option is specified.  Files may be written only if they already exist and are publicly writable, unless the --create
       option is specified.  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.  Typically, some kind of firewall or packet-filter solution should  be  employed.   If
       appropriately  compiled  (see  the  output  of in.tftpd --version) tftpd will query the hosts_access(5) database for
       access control information.  This may be slow; sites requiring maximum performance may want to compile without  this
       option and rely on firewalling or kernel-based packet filters instead.

       The  server  should be set to run as the user with the lowest possible privilege; please see the --user flag.  It is
       probably a good idea to set up a specific user account for tftpd, rather than letting it run as "nobody",  to  guard
       against privilege leaks between applications.

       Access  to  files can, and should, be restricted by invoking tftpd with a list of directories by including pathnames
       as server program arguments on the command line.  In this case access is restricted to files whole  names  are  pre‐
       fixed  by  one  of the given directories.  If possible, it is recommended that the --secure flag is used to set up a
       chroot() environment for the server to run in once a connection has been set up.

       Finally, the filename remapping (--map-file flag) support can be used to provide  a  limited  amount  of  additional
       access control.

CONFORMING TO
       RFC 1123, Requirements for Internet Hosts - Application and Support.
       RFC 1350, The TFTP Protocol (revision 2).
       RFC 2347, TFTP Option Extension.
       RFC 2348, TFTP Blocksize Option.
       RFC 2349, TFTP Timeout Interval and Transfer Size Options.

AUTHOR
       This  version  of tftpd is maintained by H. Peter Anvin <hpa@zytor.com>.  It was derived from, but has substantially
       diverged from, an OpenBSD source base, with added patches by Markus Gutschke and Gero Kulhman.

SEE ALSO
       tftp(1), egrep(1), umask(2), hosts_access(5), regex(7), inetd(8).



tftp-hpa 5.2                                         14 September 2009                                             TFTPD(8)