# rmt-tar(8) - man - phpMan [RMT(8)](https://www.chedong.com/phpMan.php/man/RMT/8/markdown) GNU TAR Manual [RMT(8)](https://www.chedong.com/phpMan.php/man/RMT/8/markdown) ## NAME rmt - remote magnetic tape server ## SYNOPSIS ### rmt ## DESCRIPTION **Rmt** provides remote access to files and devices for [**tar**(1)](https://www.chedong.com/phpMan.php/man/tar/1/markdown), [**cpio**(1)](https://www.chedong.com/phpMan.php/man/cpio/1/markdown), and similar backup util‐ ities. It is normally called by running [**rsh**(1)](https://www.chedong.com/phpMan.php/man/rsh/1/markdown) or [**ssh**(1)](https://www.chedong.com/phpMan.php/man/ssh/1/markdown) 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 read‐ ing 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 **A**_number_**\n** where _number_ is an ASCII representation of a decimal return code. Additional data are re‐ turned after this line. On error, the following response is returned: **E**_errno_**\n**_error-message_**\n** where _errno_ is one of the system error codes, as described in [**errno**(3)](https://www.chedong.com/phpMan.php/man/errno/3/markdown), and _error-message_ is a one-line human-readable description of the error, as printed by [**perror**(3)](https://www.chedong.com/phpMan.php/man/perror/3/markdown). Available commands and possible responses are discussed in detail in the subsequent section. ## COMMANDS **O**_device_**\n**_flags_**\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)](https://www.chedong.com/phpMan.php/man/open/2/markdown): 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** Close the currently open device. **Arguments** Any arguments are silently ignored. **Reply** **A0\n** on success. **L**_whence_**\n**_offset_**\n** Performs an [**lseek**(2)](https://www.chedong.com/phpMan.php/man/lseek/2/markdown) 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** **A**_offset_**\n** on success. The _offset_ is the new offset in file. **Extensions** BSD version allows only 0,1,2 as _whence_. **R**_count_**\n** Read _count_ bytes of data from the current device. **Arguments** _count_ number of bytes to read. **Reply** On success: **A**_rdcount_**\n** followed by _rdcount_ bytes of data read from the device. **W**_count_**\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: **A**_wrcount_**\n**, where _wrcount_ is the number of bytes actually written. **I**_opcode_**\n**_count_**\n** Perform a **MTIOCOP** [**ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) 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)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) call. **Arguments** None **Reply** On success: **A**_count_**\n** followed by _count_ bytes of data. ## SEE ALSO [**tar**(1)](https://www.chedong.com/phpMan.php/man/tar/1/markdown). ## BUGS Using this utility as a general-purpose remote file access tool is discouraged. ## BUG REPORTS Report bugs to <>. ## HISTORY The **rmt** command appeared in 4.2BSD. The GNU **rmt** is written from scratch, using the BSD spec‐ ification. ## COPYRIGHT Copyright © 2013, 2018 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. RMT March 24, 2018 [RMT(8)](https://www.chedong.com/phpMan.php/man/RMT/8/markdown)