NAME
	  rmt -	Allows remote access to	magnetic tape devices

     SYNOPSIS
	  rmt [debug-output-file]

     DESCRIPTION
	  The rmt command is started as	a server process when requests
	  from an rdump	or rrestore call enter the system to operate a
	  storage device through an interprocess communications	con-
	  nection.  After the remote programs have finished, rmt exits
	  and will be started again at the next	request.  The rmt com-
	  mand is normally invoked with	an rexec or rcmd system	call.

	  This process performs	the commands described in the follow-
	  ing table and	responds with a	status indication to tell a
	  user the result of the commanded process. When the rmt com-
	  mand is called with a	filename specified as the debug-
	  output-file parameter, all status responses are passed to
	  the debug-output-file	in ASCII and in	one of two possible
	  formats.  Consequently, a system administrator can debug
	  both software	and hardware problems associated with previ-
	  ously	issued backup commands to storage devices.

	  Responses to successful commands are in the format:

	   Anumber\n

	  Where	A identifies a normal response,	number is an integer
	  that defines the number of the response as an	ASCII integer,
	  and \n is a newline in the C-language	idiom.

	  Responses to unsuccessful commands are in the	format:

	   Eerror_number  error_message\n

	  Where	E identifies a response	to an error, error_number is
	  one of the possible error numbers values described in
	  intro(2), error_message is the corresponding error-message
	  string, which	is output in response to a call	to perror(3),
	  and \n is a newline.

	  Debug	information returned by	rmt is stored in the named
	  debug-output-file file. The rmt command is called from the
	  rdump	or rrestore process with no file argument only when
	  the debug-output-file	parameter is specified.	 To activate
	  the debug option of rmt your system administrator should
	  rename the original rmt to rmt.ORG, for example, and create
	  a new	shell executable rmt that calls	rmt.ORG	debug-output-
	  file.

	  All numerical	arguments of the following commands are
	  transferred as ASCII strings:

	 O  device  flag       Opens the device, which must be a full
			       pathname. The flag parameter is a flag
			       value suitable for the open system call.
			       When the	device is successfully opened,
			       the response is A0\n.

	 C  device	       Closes the current open device.	When
			       this command is successful, the response
			       is A0\n.

	 L  offset  whence     Performs	a seek operation. The offset
			       and whence parameters have the same sig-
			       nificance as the	offset and whence
			       parameters of the lseek system call.
			       When this command successfully com-
			       pletes, the response is An\n, where n
			       has the same value returned by a	nor-
			       mally successful	lseek system call.
	 W  count	       Writes data to the device (see the O
			       command above). The rmt command reads
			       count bytes from	the connection.	This
			       process is aborted when an EOF (End-of-
			       File) is	detected before	the number of
			       characters specified by count is
			       transferred. The	response to this com-
			       mand is An\n, where n is	the number of
			       characters written.
	 R  count	       Reads count bytes of data from the open
			       device. When the	value of count exceeds
			       the size	of the data buffer (10 kilo-
			       bytes), the number of characters	read is
			       truncated to the	data buffer size. The
			       rmt command then	does the requested read
			       operation. The response to this command
			       is An\n,	where n	is the number of char-
			       acters read.














	 I  operation  count   Performs	an ioctl system	call on	the
			       open device. The	operation parameter is
			       a value passed to the mt_op member of a
			       type mtop structure for an MTIOCTOP
			       ioctl (magnetic tape operation) command.
			       Valid values for	the magnetic tape
			       operations are defined in the
			       /usr/include/sys/mtio.h include file.
			       The count parameter is the value	to pass
			       to the mt_count member of the type mtop
			       structure and specifies the number of
			       operations performed on the tape	drive.
			       The response to this command is
			       An\n,where n is the count.
	 S		       Returns the status of the open device,
			       which is	obtained with a	MTIOCGET ioctl
			       system call. A successful response to
			       this command is An\n, where n is	the
			       size of the status buffer, together with
			       the contents of the status buffer in
			       binary.

     FILES
	  /usr/sbin/rmt
	       Specifies the command path

	  /usr/include/errno.h
	       Describes the possible error numbers.

	  /usr/include/sys/mtio.h
	       A header	file that defines magnetic tape	operations.

     RELATED INFORMATION
	  Commands:  rdump(8), rrestore(8).

	  System calls:	rcmd(3), rexec(3), open(2), ioctl(2)