Which tar file format should I use?

Question

tar can create the archive in different formats. GNU tar, ustar, pax, v7. What would be the best for long time archiving? Is there significant differencies in these formats?

I would use the best format for general backups, and I don't want that maybe I can extract the data, because format problems. (v7 is disappear from implementation for example)

Answer 1

The GNU tar manual actually has [an entire section dedicated for tar archive formats. The formats ustar and pax are based on POSIX standards, and gnu is very widespread. I'd steer clear from the other ones.

My suggestion would be to choose pax, that is POSIX.1-2001. GNU tar is making it the default in the future and even old ustar implementations can decompress it. It's also the least restricting format.

You can create POSIX.1-2001 archives e.g. with GNU tar by specifying --format pax or with a separate pax archiver.

Answer 2

pax is POSIX compliant... That having been said, I only use tar, tar+gz and tar+bz2

Answer 3

tar.gz is the fairly standard one.

tar archives all the files into a single file, like .iso, but it doesn't compress those.

gzip (gz) will compress the tar files.

The *nix command line to perform this is:

tar -pczf name-of-new-archive.tar.gz /path/of/the/directory