RMT(8) System Manager's Manual RMT(8)
NAME
rmt - remote magtape protocol module
SYNOPSIS
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(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 indica-
tion. All responses are in ASCII and in one of two forms. Successful commands have responses of
Anumber
where number is an ASCII representation of a decimal number. Unsuccessful commands are responded to with
Eerror-number
error-message
,
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 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 dec-
imal number suitable for passing to open(2). If a device had already been opened, it is closed before a new open is per-
formed.
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 encoun-
tered. 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
if the read was success-
ful; 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 representa-
tions 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(3), rexec(3), mtio(4), rdump(8), rrestore(8)
BUGS
People tempted to use this for a remote file access protocol are discouraged.
4.2 Berkeley Distribution November 17, 1996 RMT(8)
