RMT(8) GNU TAR Manual RMT(8)

# [NAME](#NAME)

rmt - remote magnetic tape server

# [SYNOPSIS](#SYNOPSIS)

**rmt**

# [DESCRIPTION](#DESCRIPTION)

**Rmt** provides remote access to files and devices for [**tar**(1)](/man/os/cpio/tar.1), [**cpio**(1)](/man/os/cpio/cpio.1), and similar backup utilities. It is normally called by running [**rsh**(1)](/man/os/cpio/rsh.1) or [**ssh**(1)](/man/os/cpio/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 character. 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)](/man/os/cpio/errno.3), and *error-message* is a one-line human-readable description of the error, as printed by [**perror**(3)](/man/os/cpio/perror.3).

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

# [COMMANDS](#COMMANDS)

[**Odevice\\nflags\\n**](#O)

Opens the *device* with given *flags*. If a device had already been opened, it is closed before opening the new one.

**Arguments**

[*device*](#device)

The name of the device to open.

[*flags*](#flags)

Flags for [**open**(2)](/man/os/cpio/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 representation. 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**](#C)

Close the currently open device.

[**Arguments**](#Arguments)

Any arguments are silently ignored.

[**Reply**](#Reply)

**A0\\n** on success.

[**Lwhence\\noffset\\n**](#L)

Performs an [**lseek**(2)](/man/os/cpio/lseek.2) on the currently open device with the specified parameters.

[**Arguments**](#Arguments~2)

[*whence*](#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**](#Reply~2)

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

[**Extensions**](#Extensions)

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

[**Rcount\\n**](#R)

Read *count* bytes of data from the current device.

[**Arguments**](#Arguments~3)

[*count*](#count)

number of bytes to read.

[**Reply**](#Reply~3)

On success:

**Ardcount\\n**

followed by *rdcount* bytes of data read from the device.

[**Wcount\\n**](#W)

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

[**Arguments**](#Arguments~4)

[*count*](#count~2)

Number of bytes to write.

[**Reply**](#Reply~4)

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

[**Iopcode\\ncount\\n**](#I)

Perform a **MTIOCOP** [**ioctl**(2)](/man/os/cpio/ioctl.2) command with the specified paramedters.

[**Arguments**](#Arguments~5)

[*opcode*](#opcode)

**MTIOCOP** operation code.

[*count*](#count~3)

mt\_count.

[**Reply**](#Reply~5)

On success: **A0\\n**.

[**S\\n**](#S)

Returns the status of the currently open device, as obtained from a **MTIOCGET** [**ioctl**(2)](/man/os/cpio/ioctl.2) call.

[**Arguments**](#Arguments~6)

None

[**Reply**](#Reply~6)

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

# [SEE ALSO](#SEE_ALSO)

[**tar**(1)](/man/os/cpio/tar.1).

# [BUGS](#BUGS)

Using this utility as a general-purpose remote file access tool is discouraged.

# [BUG REPORTS](#BUG_REPORTS)

Report bugs to <bug-tar@gnu.org>.

# [HISTORY](#HISTORY)

The **rmt** command appeared in 4.2BSD. The GNU **rmt** is written from scratch, using the BSD specification.

# [COPYRIGHT](#COPYRIGHT)

Copyright © 2013, 2018 Free Software Foundation, Inc.  
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>  
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

March 24, 2018 RMT

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Document: rmt(8) from cpio 2.15-r13 (Chainguard OS)
Source: https://git.savannah.gnu.org/git/cpio.git