The website "The Tao of Backup" (http://www.taobackup.com) describes seven points to remember when devising a backup strategy.

  1. Coverage - do you back up all your files? You might think that there isn't much point in backing up the operating system files, because you could just reinstall, but if you've put a lot of work into configuring the operating system, you don't want to have to do it again.
  2. Frequency - how often do you back up your files? If it's only occasionally, you may lose several weeks' work when your hard drive crashes. It's best to set up a cron job or equivalent so that the backups run automatically every night and all you have to do is change the tapes.
  3. Separation - keep some offsite backups. If you don't, your computer and all your backups may be destroyed in a fire. Ideally, keep them in another city to protect against hurricanes and earthquakes.
  4. History - what range of dates do your backups cover? If you discovered that you had accidentally deleted an important file three months ago, or that a virus attack had been slowly corrupting your data, would you be able to recover from your backup tapes?
  5. Testing - the only way you can know whether your backups work is to restore from them. Remember, sometimes backup programs falsely claim to have written the data successfully. Also, the tapes may be poor quality or have been exposed to a magnet. Test your backups regularly, because even if you tested them in the past, something may have changed since then.
  6. Security - are your backup tapes kept in a locked safe, or could an intruder walk off with one of them? If he did, he'd have access to all your users' private files, unless your backups are encrypted. Even sysadmins who are good at keeping their systems secure often forget that the backup tapes can be a security hole.
  7. Integrity - if your original data is corrupt, for example because a cracker broke into your system, and you don't know when the corruption began, then your backups won't help you, because they'll only contain copies of the corrupt data. Use a tool such as aide or Tripwire to check for unexpected changes to system files.