RMT(8C)RMT(8C)NAMErmt - remote magtape protocol module
SYNOPSIS
/usr/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). 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 ALSOrcmd(3X), rexec(3X), mtio(4), rdump(8C), rrestore(8C)BUGS
People tempted to use this for a remote file access protocol are
discouraged.
4.2 Berkeley Distribution April 27, 1985 RMT(8C)
