BSD 2.11 - man page for rmt (bsd section 8)
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rmt - remote magtape protocol module
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(3) or rcmd(3) 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
where number is an ASCII representation of a decimal number. Unsuccessful commands are
responded to with
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). The proto-
col 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 path-
name 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 connec-
tion, 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 val-
ues 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
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.
All responses are of the form described above.
rcmd(3), rexec(3), mtio(4), rdump(8), rrestore(8)
People tempted to use this for a remote file access protocol are discouraged.
4.2 Berkeley Distribution November 17, 1996 RMT(8)
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