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RMT(8)                    BSD System Manager's Manual                   RMT(8)


     rmt -- remote magtape protocol module




     The rmt utility is used by the remote dump and restore programs in manip-
     ulating a magnetic tape drive through an interprocess communication con-
     nection.  It is normally started up with an rexec(3) or rcmd(3) call.

     The rmt utility 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:


     Number is an ASCII representation of a decimal number.  Unsuccessful com-
     mands are responded to with:


     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).  The protocol is comprised of the following commands,
     which are sent as indicated - no spaces are supplied between the command
     and its arguments, or between its arguments, and `\n' indicates that a
     newline should be supplied:

             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.

             Close the currently open device.  The device specified is

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

             Write data onto the open device.  The rmt utility 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.

             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.  The rmt utility 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

             Perform a MTIOCOP ioctl(2) command using the specified parame-
             ters.  The parameters are interpreted as the ASCII representa-
             tions of the decimal values to place in the mt_op and mt_count
             fields of the structure used in the ioctl(2) 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(2) 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.


     All responses are of the form described above.


     rcmd(3), rexec(3), mtio(4), rdump(8), rrestore(8)


     People should be discouraged from using this for a remote file access


     The rmt utility appeared in 4.2BSD.

BSD                              June 1, 1994                              BSD

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