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 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.