rmt(1M) rmt(1M)
NAME [Toc] [Back]
rmt - remote magnetic-tape protocol module
SYNOPSIS [Toc] [Back]
/usr/sbin/rmt
DESCRIPTION [Toc] [Back]
rmt is a program used by the remote dump and restore programs for
manipulating a magnetic tape drive through an interprocess
communication (IPC) connection. The fbackup and frecover commands
also use rmt to achieve remote backup capability (see fbackup(1M) and
frecover(1M)). rmt is normally started up with an rexec() or rcmd()
call (see rexec(3N) and rcmd(3N)).
rmt accepts requests specific to the manipulation of magnetic tapes,
performs the commands, then responds with a status indication. DDS
devices that emulate magnetic tapes are also supported. 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
errno(2) and error-message is the corresponding error string as
printed from a call to perror() (see perror(3C)). The protocol is
comprised of the following commands:
Odevice\nmode\n 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() (see open(2)). If a device is
already open, it is closed before a new open
is performed.
odevice\nmode\n Open the specified device using the
indicated mode. device is a full pathname
and mode is an ASCII representation of an
octal number suitable for passing to open().
If a device is already open, it is closed
before a new open is performed.
Cdevice\n Close the currently open device. The device
specified is ignored.
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rmt(1M) rmt(1M)
Lwhence\noffset\n Perform an lseek() operation using the
specified parameters (see lseek(2)). The
response value is that returned from by
lseek().
Wcount\n 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 by
write() (see write(2)).
Rcount\n Read count bytes of data from the open
device. If count exceeds the size of the
data buffer (10 Kbytes), it is truncated to
the data buffer size. rmt then performs the
requested read() and responds with Acount-
read\n if the read was successful.
Otherwise an error is returned in the
standard format. If the read was
successful, the data read is then sent.
Ioperation\ncount\n Perform a MTIOCOP ioctl() command using the
specified parameters. Parameters are
interpreted as ASCII representations of the
decimal values to be placed 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).
s Return the status of the open device, as
obtained with a fstat() 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). f Return
the status of the open device, as obtained
with a fstat() call. If the operation was
successful, an ACK is sent with the size of
the status buffer, then the status buffer is
sent in the following ASCII format:
machine<blank>value<newline>
stat_struct_member_name<blank>value<newline>
The end of the data is indicated by an ASCII
NULL character. See /usr/include/sys/stat.h
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rmt(1M) rmt(1M)
for the struct stat definition. In addition
to the struct stat information, there is an
entry in the buffer describing the machine
type as returned from a uname() call (see
uname(2)). In the above format ``machine''
is a key word. All fields except st_spare4
of the struct stat are returned.
m 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 the following ASCII
format:
machine<blank>value<newline>
mtget_struct_member_name<blank>value<newline>
The end of the data is indicated by an ASCII
NULL character. See /usr/include/sys/mtio.h
for the struct mtget definition. In
addition to the struct mtget information
there is an entry in the buffer describing
the machine type as returned from a uname()
call. In the above format ``machine'' is a
keyword.
Any other command causes rmt to exit.
RETURN VALUE [Toc] [Back]
Device status is returned in the field mt_gstat.
/usr/include/sys/mtio.h contains defined macros for checking the
status bits.
DIAGNOSTICS [Toc] [Back]
All responses are of the form described above.
AUTHOR [Toc] [Back]
rmt was developed by the University of California, Berkeley.
SEE ALSO [Toc] [Back]
ftio(1), fbackup(1M), frecover(1M), dump(1M), restore(1M), rcmd(3N),
rexec(3N).
WARNINGS [Toc] [Back]
Use of this command for remote file access protocol is discouraged.
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