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Use archive file or device file on hostname.
This option is used to specify the file name of the archive
If the file name is ‘-’,
tar reads the archive from standard
input (when listing or extracting), or writes it to standard output
(when creating). If the ‘-’ file name is given when updating an
tar will read the original archive from its standard
input, and will write the entire new archive to its standard output.
If the file name contains a ‘:’, it is interpreted as
‘hostname:file name’. If the hostname contains an at
sign (‘@’), it is treated as ‘user@hostname:file name’. In
tar will invoke the command
remsh) to start up an
/usr/libexec/rmt on the remote
machine. If you give an alternate login name, it will be given to the
Naturally, the remote machine must have an executable
/usr/libexec/rmt. This program is free software from the
University of California, and a copy of the source code can be found
with the sources for
tar; it’s compiled and installed by default.
The exact path to this utility is determined when configuring the package.
It is ‘prefix/libexec/rmt’, where prefix stands for
your installation prefix. This location may also be overridden at
runtime by using the ‘--rmt-command=command’ option (See section —rmt-command, for detailed description of this option. See section Remote Tape Server, for the description of
If this option is not given, but the environment variable
is set, its value is used; otherwise, old versions of
used a default archive name (which was picked when
compiled). The default is normally set up to be the first tape
drive or other transportable I/O medium on the system.
Starting with version 1.11.5, GNU
standard input and standard output as the default device, and I will
not try anymore supporting automatic device detection at installation
time. This was failing really in too many cases, it was hopeless.
This is now completely left to the installer to override standard
input and standard output for default device, if this seems
preferable. Further, I think most actual usages of
tar are done with pipes or disks, not really tapes,
cartridges or diskettes.
Some users think that using standard input and output is running after trouble. This could lead to a nasty surprise on your screen if you forget to specify an output file name—especially if you are going through a network or terminal server capable of buffering large amounts of output. We had so many bug reports in that area of configuring default tapes automatically, and so many contradicting requests, that we finally consider the problem to be portably intractable. We could of course use something like ‘/dev/tape’ as a default, but this is also running after various kind of trouble, going from hung processes to accidental destruction of real tapes. After having seen all this mess, using standard input and output as a default really sounds like the only clean choice left, and a very useful one too.
tar reads and writes archive in records, I
suspect this is the main reason why block devices are preferred over
character devices. Most probably, block devices are more efficient
too. The installer could also check for ‘DEFTAPE’ in
Archive file is local even if it contains a colon.
Use remote command instead of
rsh. This option exists
so that people who use something other than the standard
(e.g., a Kerberized
rsh) can access a remote device.
When this command is not used, the shell command found when
tar program was installed is used instead. This is
the first found of ‘/usr/ucb/rsh’, ‘/usr/bin/remsh’,
‘/usr/bin/rsh’, ‘/usr/bsd/rsh’ or ‘/usr/bin/nsh’.
The installer may have overridden this by defining the environment
RSH at installation time.
Specify drive and density.
Create/list/extract multi-volume archive.
This option causes
tar to write a multi-volume archive—one
that may be larger than will fit on the medium used to hold it.
See section Archives Longer than One Tape or Disk.
Change tape after writing size units of data. Unless suf is given, size is treated as kilobytes, i.e. ‘size x 1024’ bytes. The following suffixes alter this behavior:
|b||Blocks||size x 512|
|B||Kilobytes||size x 1024|
|G||Gigabytes||size x 1024^3|
|K||Kilobytes||size x 1024|
|k||Kilobytes||size x 1024|
|M||Megabytes||size x 1024^2|
|P||Petabytes||size x 1024^5|
|T||Terabytes||size x 1024^4|
|w||Words||size x 2|
Table 9.1: Size Suffixes
This option might be useful when your tape drivers do not properly detect end of physical tapes. By being slightly conservative on the maximum tape length, you might avoid the problem entirely.
Execute command at end of each tape. This implies ‘--multi-volume’ (‘-M’). See info-script, for a detailed description of this option.
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