rmt(8)
NAME
rmt - remote magtape protocol module
SYNOPSIS
/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(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
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 MTIOCTOP 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 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.
Minix-vmd doesn't have the dump(8) and restore(8) programs yet, but
thanks to rmt you can use a tape drive attached to a Minix-vmd system
remotely.