Introduction to Dump
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.