(tar.info.gz) Date input formats
8 Controlling the Archive Format
Due to historical reasons, there are several formats of tar archives.
All of them are based on the same principles, but have some subtle
differences that often make them incompatible with each other.
GNU tar is able to create and handle archives in a variety of
formats. The most frequently used formats are (in alphabetical order):
Format used by GNU `tar' versions up to 1.13.25. This format
derived from an early POSIX standard, adding some improvements
such as sparse file handling and incremental archives.
Unfortunately these features were implemented in a way
incompatible with other archive formats.
Archives in `gnu' format are able to hold file names of unlimited
Format used by GNU `tar' of versions prior to 1.12.
Archive format, compatible with the V7 implementation of tar. This
format imposes a number of limitations. The most important of them
1. The maximum length of a file name is limited to 99 characters.
2. The maximum length of a symbolic link is limited to 99
3. It is impossible to store special files (block and character
devices, fifos etc.)
4. Maximum value of user or group ID is limited to 2097151
5. V7 archives do not contain symbolic ownership information
(user and group name of the file owner).
This format has traditionally been used by Automake when producing
Makefiles. This practice will change in the future, in the
meantime, however this means that projects containing file names
more than 99 characters long will not be able to use GNU `tar'
1.23 and Automake prior to 1.9.
Archive format defined by POSIX.1-1988 specification. It stores
symbolic ownership information. It is also able to store special
files. However, it imposes several restrictions as well:
1. The maximum length of a file name is limited to 256
characters, provided that the file name can be split at a
directory separator in two parts, first of them being at most
155 bytes long. So, in most cases the maximum file name
length will be shorter than 256 characters.
2. The maximum length of a symbolic link name is limited to 100
3. Maximum size of a file the archive is able to accommodate is
4. Maximum value of UID/GID is 2097151.
5. Maximum number of bits in device major and minor numbers is
Format used by Jo"rg Schilling `star' implementation. GNU `tar'
is able to read `star' archives but currently does not produce
Archive format defined by POSIX.1-2001 specification. This is the
most flexible and feature-rich format. It does not impose any
restrictions on file sizes or file name lengths. This format is
quite recent, so not all tar implementations are able to handle it
properly. However, this format is designed in such a way that any
tar implementation able to read `ustar' archives will be able to
read most `posix' archives as well, with the only exception that
any additional information (such as long file names etc.) will in
such case be extracted as plain text files along with the files it
refers to. This is the only format that can store ACLs, SELinux
context and extended attributes.
This archive format will be the default format for future versions
of GNU `tar'.
The following table summarizes the limitations of each of these
Format UID File Size File Name Devn
gnu 1.8e19 Unlimited Unlimited 63
oldgnu 1.8e19 Unlimited Unlimited 63
v7 2097151 8GB 99 n/a
ustar 2097151 8GB 256 21
posix Unlimited Unlimited Unlimited Unlimited
The default format for GNU `tar' is defined at compilation time.
You may check it by running `tar --help', and examining the last lines
of its output. Usually, GNU `tar' is configured to create archives in
`gnu' format, however, future version will switch to `posix'.
* Compression Using Less Space through Compression
* Attributes Handling File Attributes
* Portability Making `tar' Archives More Portable
* cpio Comparison of `tar' and `cpio'
(tar.info.gz) Date input formats
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