Practical UNIX and Internet Security, 3rd Edition

Chapter 18: Backups

• Make regular backups.

• Be certain that everything on your system is backed up.

• Formulate a written backup plan. Remember to update your plan whenever you update your system or change its configuration.

• Make paper copies of critical files for comparison or rebuilding your system (e.g., /etc/passwd, /etc/rc, and /etc/fstab).

• Make at least every other backup onto a different tape to guard against media failure.

• Do not reuse a backup tape too many times because the tapes will eventually fail.

• Try to restore a few files from your backups on a regular basis.

• Make periodic archive backups of your entire system and keep them forever.

• Try to completely rebuild your system from a set of backups to be certain that your backup procedures are complete.

• Keep your backups under lock and key.

• Do not store your backups in the same room as your computer system: consider offsite backup storage.

• Ensure that access to your backups during transport and storage is limited to authorized and trusted individuals.

• If your budget and needs are appropriate, investigate doing backups across a network link to a “hot spare” site.

• Encrypt your backups, but escrow the keys in case you lose them.

• When using software that accesses files directly rather than through the raw devices, consider remounting the filesystems as read-only during backups to prevent changes to file access times.