8.3.6 GNU and old GNU tar format

GNU tar was based on an early draft of the POSIX 1003.1 ustar standard. GNU extensions to tar, such as the support for file names longer than 100 characters, use portions of the tar header record which were specified in that POSIX draft as unused. Subsequent changes in POSIX have allocated the same parts of the header record for other purposes. As a result, GNU tar format is incompatible with the current POSIX specification, and with tar programs that follow it.

In the majority of cases, tar will be configured to create this format by default. This will change in future releases, since we plan to make ‘POSIX’ format the default.

To force creation a GNU tar archive, use option ‘--format=gnu’.

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