RMT(8C)                              BSD                               RMT(8C)



NAME
     rmt - remote magtape protocol module

SYNOPSIS
     /etc/rmt

DESCRIPTION
     rmt is a program used by the remote dump and restore programs in
     manipulating a magnetic tape drive through an interprocess communication
     connection.  rmt is normally started up with an rexec(3X) or rcmd(3X)
     call.

     The rmt program accepts requests specific to the manipulation of magnetic
     tapes, performs the commands, then responds with a status indication.
     All responses are in ASCII and in one of two forms. Successful commands
     have responses of

          Anumber\n

     where number is an ASCII representation of a decimal number.
     Unsuccessful commands are responded to with

          Eerror-number\nerror-message\n,

     where error-number is one of the possible error numbers described in
     intro(2) and error-message is the corresponding error string as printed
     from a call to perror(3).

COMMANDS
     The protocol is comprised of the following commands (a space is present
     between each token).

     O device mode  Open the specified device using the indicated mode.
                    Device is a full pathname and mode is an ASCII
                    representation of a decimal number suitable for passing to
                    open(2).  If a device had already been opened, it is
                    closed before a new open is performed.

     C device       Close the currently open device.  The device specified is
                    ignored.

     L whence offset
                    Perform an lseek(2) operation using the specified
                    parameters.  The response value is that returned from the
                    lseek call.

     W count        Write data onto the open device.  rmt reads count bytes
                    from the connection, aborting if a premature end-of-file
                    is encountered.  The response value is that returned from
                    the write(2) call.

     R count        Read count bytes of data from the open device.  If count
                    exceeds the size of the data buffer (10 kilobytes), it is
                    truncated to the data buffer size.  rmt then performs the
                    requested read(2) and responds with Acount-read\n if the
                    read was successful; otherwise an error in the standard
                    format is returned.  If the read was successful, the data
                    read is then sent.

     I operation count
                    Perform a MTIOCOP ioctl(2) command using the specified

                    parameters.  The parameters are interpreted as the ASCII
                    representations of the decimal values to place in the
                    mt_op and mt_count fields of the structure used in the
                    ioctl call.  The return value is the count parameter when
                    the operation is successful.

     S              Return the status of the open device, as obtained with a
                    MTIOCGET ioctl call.  If the operation was successful, an
                    "ack" is sent with the size of the status buffer, then the
                    status buffer is sent (in binary).

     Any other command causes rmt to exit.

DIAGNOSTICS
     All responses are of the form described above.

SEE ALSO
     rcmd(3X), rexec(3X), mtio(4), rdump(8C), rrestore(8C)

BUGS
     People tempted to use this for a remote file access protocol are
     discouraged.