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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 new-
       line.  On success, rmt returns

	   Anumber\n

       where number is an ASCII	representation of a decimal return code.   Ad-
       ditional	 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 er-
       ror, 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 dec-
		     imal  mode	 followed  by its symbolic representation.  In
		     this case the symbolic representation  is	given  prefer-
		     ence.

	      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 spec-
	      ified 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 dis-
       couraged.

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 (C) 2013, 2018	Free Software Foundation, Inc.
       License GPLv3+: GNU GPL version 3 or later <http://gnu.org/li-
       censes/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)

NAME | SYNOPSIS | DESCRIPTION | COMMANDS | SEE ALSO | BUGS | BUG REPORTS | HISTORY | COPYRIGHT

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