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