Manual: rmt

RMT(8) GNU TAR Manual RMT(8)

NAME
rmt - remote magnetic tape server

SYNOPSIS
rmt

DESCRIPTION
Rmt provides remote access to files and devices for tar(1), cpio(1), and similar backup utilities. It is normally
called by running rsh(1) or ssh(1) to the remote machine, optionally using a different login name if one is supplied.

The calling program communicates with rmt by sending requests on its standard input and reading replies from the
standard output. A request consists of a request letter followed by an argument (if required) and a newline charac‐
ter. Additional data, if any, are sent after the newline. On success, rmt returns

Anumber\n

where number is an ASCII representation of a decimal return code. Additional data are returned after this line. On
error, the following response is returned:

Eerrno\nerror-message\n

where errno is one of the system error codes, as described in errno(3), and error-message is a one-line human-read‐
able description of the error, as printed by perror(3).

Available commands and possible responses are discussed in detail in the subsequent section.

COMMANDS
Odevice\nflags\n
Opens the device with given flags. If a device had already been opened, it is closed before opening the new
one.

Arguments

device The name of the device to open.

flags Flags for open(2): a decimal number, or any valid O_* constant from fcntl.h (the initial O_ may be
omitted), or a bitwise or (using |) of any number of these, e.g.:
576
64|512
CREAT|TRUNC
In addition, a combined form is also allowed, i.e. a decimal mode followed by its symbolic representa‐
tion. In this case the symbolic representation is given preference.

Reply
A0\n on success.

Extensions
BSD version allows only decimal number as flags.

C[device]\n
Close the currently open device.

Arguments
Any arguments are silently ignored.

Reply
A0\n on success.

Lwhence\noffset\n
Performs an lseek(2) on the currently open device with the specified parameters.

Arguments

whence Where to measure offset from. Valid values are:

0, SET, SEEK_SET seek from the file beginning
1, CUR, SEEK_CUR seek from the current location
2, END, SEEK_END seek from the file end

Reply
Aoffset\n on success. The offset is the new offset in file.

Extensions
BSD version allows only 0,1,2 as whence.

Rcount\n
Read count bytes of data from the current device.

Arguments

count number of bytes to read.

Reply
On success:

Ardcount\n

followed by rdcount bytes of data read from the device.

Wcount\n
Writes data onto the current device. The command is followed by count bytes of input data.

Arguments

count Number of bytes to write.

Reply
On success: Awrcount\n, where wrcount is the number of bytes actually written.

Iopcode\ncount\n
Perform a MTIOCOP ioctl(2) command with the specified paramedters.

Arguments

opcode MTIOCOP operation code.

count mt_count.

Reply
On success: A0\n.

S\n Returns the status of the currently open device, as obtained from a MTIOCGET ioctl(2) call.

Arguments
None

Reply
On success: Acount\n followed by count bytes of data.

Manual: rmt

Related Commands: