Verifying the integrity of files is an important systems administration task. Well-known systems administration authority Aeleen Frisch says that "minimally, you should periodically check the ownership and permissions of important system files and directories." One method for verifying files is to take a snapshot of the system in a pristine state and compare it against subsequent snapshots.

You can use a product such as Tripwire, or create your own such as our Entrap utility. Entrap is a suite of Korn shell scripts that compares two snapshots of a system and reports the differences. When two snapshots are compared, Entrap reports information about files that have been added, deleted, and modified.

By Ed Schaefer and John Spurgeon at UNIX Review.

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