Using the dump utility to back up Unix-based files can be a tricky undertaking. The following excerpt from W. Curtis Preston's new book, Backup & Recovery: Inexpensive Backup Solutions for Open Systems, explains how dump works and tells what can go wrong at various stages of the dump backup process.

cpio, ntbackup, and tar are filesystem-based utilities that access files through the filesystem. If a backup file is changed, deleted, or added during a backup, usually the worst thing that can happen is that the contents of the individual file that changed will be corrupt. Unfortunately, there is one huge disadvantage to backing up files through the filesystem: the backup affects inode times--in a Unix-based operating system, an inode is a stored description of an individual file--(atime or ctime).