RMT(8)				GNU TAR Manual				RMT(8)

NAME
       rmt - remote magnetic tape server

SYNOPSIS
       rmt

DESCRIPTION
       Rmt provides remote access to files and devices for tar(1), cpio(1),
       and similar backup utilities.  It is normally called by running rsh(1)
       or ssh(1) to the remote machine, optionally using a different login
       name if one is supplied.

       The calling program communicates with rmt by sending requests on its
       standard input and reading replies from the standard output.  A request
       consists of a request letter followed by an argument (if required) and
       a newline character.  Additional data, if any, are sent after the
       newline.	 On success, rmt returns

	   Anumber\n

       where number is an ASCII representation of a decimal return code.
       Additional data are returned after this line.  On error, the following
       response is returned:

	   Eerrno\nerror-message\n

       where errno is one of the system error codes, as described in errno(3),
       and error-message is a one-line human-readable description of the
       error, as printed by perror(3).

       Available commands and possible responses are discussed in detail in
       the subsequent section.

COMMANDS
       Odevice\nflags\n
	      Opens the device with given flags. If a device had already been
	      opened, it is closed before opening the new one.

	      Arguments

	      device The name of the device to open.

	      flags  Flags for open(2): a decimal number, or any valid O_*
		     constant from fcntl.h (the initial O_ may be omitted), or
		     a bitwise or (using |) of any number of these, e.g.:
			 576
			 64|512
			 CREAT|TRUNC
		     In addition, a combined form is also allowed, i.e. a
		     decimal mode followed by its symbolic representation.  In
		     this case the symbolic representation is given
		     preference.

	      Reply
		     A0\n on success.

	      Extensions
		     BSD version allows only decimal number as flags.

       C[device]\n
	      Close the currently open device.

	      Arguments
		     Any arguments are silently ignored.

	      Reply
		     A0\n on success.

       Lwhence\noffset\n
	      Performs an lseek(2) on the currently open device with the
	      specified parameters.

	      Arguments

		     whence Where to measure offset from. Valid values are:

			     0, SET, SEEK_SET	seek from the file beginning
			     1, CUR, SEEK_CUR	seek from the current location
			     2, END, SEEK_END	seek from the file end

	      Reply
		     Aoffset\n on success. The offset is the new offset in
		     file.

	      Extensions
		     BSD version allows only 0,1,2 as whence.

       Rcount\n
	      Read count bytes of data from the current device.

	      Arguments

		     count  number of bytes to read.

	      Reply
		     On success:

			 Ardcount\n

	      followed by rdcount bytes of data read from the device.

       Wcount\n
	      Writes data onto the current device.  The command is followed by
	      count bytes of input data.

	      Arguments

		     count  Number of bytes to write.

	      Reply
		     On success: Awrcount\n, where wrcount is the number of
		     bytes actually written.

       Iopcode\ncount\n
	      Perform a MTIOCOP ioctl(2) command with the specified
	      paramedters.

	      Arguments

		     opcode MTIOCOP operation code.

		     count  mt_count.

	      Reply
		     On success: A0\n.

       S\n    Returns the status of the currently open device, as obtained
	      from a MTIOCGET ioctl(2) call.

	      Arguments
		     None

	      Reply
		     On success: Acount\n followed by count bytes of data.

SEE ALSO
       tar(1).

BUGS
       Using this utility as a general-purpose remote file access tool is
       discouraged.

BUG REPORTS
       Report bugs to <bug-tar@gnu.org>.

HISTORY
       The rmt command appeared in 4.2BSD.  The GNU rmt is written from
       scratch, using the BSD specification.

COPYRIGHT
       Copyright © 2013, 2018 Free Software Foundation, Inc.
       License GPLv3+: GNU GPL version 3 or later
       <http://gnu.org/licenses/gpl.html>
       This is free software: you are free to change and redistribute it.
       There is NO WARRANTY, to the extent permitted by law.

RMT				March 24, 2018				RMT(8)