RMT(8) Maintenance Procedures RMT(8)


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(3SOCKET) or
rcmd(3SOCKET) call.

The rmt program accepts requests that are 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

Unsuccessful commands are responded to with:


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

The protocol consists of the following commands:

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).

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

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. When the operation is successful
the return value is the count parameter.

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

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(9E). If a device is
already open, it is closed before a new open is

Read count bytes of data from the open device.
rmt performs the requested read(9E) and responds
with Acount-read\n if the read was successful;
otherwise an error in standard format is
returned. If the read was successful, the data
read is sent.

Write data onto the open device. rmt reads count
bytes from the connection, aborting if a
premature EOF is encountered. The response value
is returned from the write(9E) call.

Any other command causes rmt to exit.


ioctl(2), lseek(2), Intro(3), perror(3C), rcmd(3SOCKET), rexec(3SOCKET),
mtio(4I), attributes(7), ufsdump(8), ufsrestore(8), open(9E), read(9E),


All responses are of the form described above.


Do not use this for a remote file access protocol.

November 6, 2000 RMT(8)