Which tar file format should I use

archivebackupformattar

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)

Best Answer

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.

Related Solutions

Linux – How well does backupexec work with Linux and archive format

Both NetBackup and Backup Exec use proprietary tape formats. I know that current versions of NetBackup can read the Backup Exec tape format, but AFAIK the converse (Backup Exec reading the NetBackup tape format) doesn't work.

I've only had a bit of experience with Backup Exec on Linux, so I'll leave my comments at: It backed-up the files we needed reliably. We never did a disaster recovery of any of the Linux machines that were covered strictly from tape. We opted, instead, to reinstall their OS and then restore data files from backup where necessary.

Tar File Checksum – Creating a Tar File with Checksums Included

Before going ahead and rewriting tar, you may want to profile the quick-and-easy method of reading the data twice, as it may not be much slower than doing it in one pass.

The two pass method is implented here:

http://www.g-loaded.eu/2007/12/01/veritar-verify-checksums-of-files-within-a-tar-archive/

with the one-liner:

  tar -cvpf mybackup.tar myfiles/| xargs -I '{}' sh -c "test -f '{}' && 
  md5sum '{}'" | tee mybackup.md5

While its true that md5sum is reading each file from disk in parallel with tar, instead of getting the data streamed through the pipe, Linux disk cacheing should make this second read a simple read from a memory buffer, which shouldn't really be slower than a stdin read. You just need to make sure you have enough space in your disk cache to store enough of each file that the 2nd reader is always reading from the cache and not getting far enough behind to have to retrieve from disk

Best Answer

Related Solutions

Linux – How well does backupexec work with Linux and archive format

Tar File Checksum – Creating a Tar File with Checksums Included

Related Topic