Linux Shell Scripting Cookbook - Third Edition

Differential archives

The backup solutions described so far are full copies of a filesystem as it exists at that time. This snapshot is useful when you recognize a problem immediately and need the most recent snapshot to recover. It fails if you don't realize the problem until a new snapshot is made and the previous good data has been overwritten by current bad data.

An archive of a filesystem provides a history of file changes. This is useful when you need to return to an older version of a damaged file.

rsync, tar, and cpio can be used to make daily snapshots of a filesystem. However, backing up a full filesystem every day is expensive. Creating a separate snapshot for each day of the week will require seven times as much space as the original ...