Everything is Linux

Monday, December 1, 2008

Introduction to Dump

Dump: Smart Archiver for Filesystems, not FilesThere are other popular tools to manage backup archives such as cpio, tar and afio.
These utilities handle files as the target to be archived and they are capable of excluding specific files and/or directories from the target.
They can even create a single archive that contains files from multiple filesystems.In contrast, dump handles a physical filesystem as an archiving target and the restore command usually uses the archive to restore the filesystem as it was dump’ed.
Each file is managed by the i-node number and basically, dump cannot exclude specific files from the archive (actually, you may do so in a different manner.

Dump is indeed a simplistic and primitive tool, but it does come with a brilliant feature for incremental archiving. It identifies newly created or modified files after the previous backup and efficiently stores them to an archive very fast.

For example, suppose a file ‘foo’ was backed up during the last archiving and removed afterwards. On the next incremental archiving, dump puts the record in the archive as ‘there used to be a file foo, but it was removed’.
If you use tar for your regular incremental backup tasks and attempt a full restoration one day, you may run out of the disk space by trying to restore a large number of files that had already been removed.
With dump, you will never face such a problem.In summary, it would be fair to say² Cpio, tar or afio is suitable for archiving specific files or directories.² Dump is suitable for archiving whole filesystems.Just pick a right tool for you job.



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