3.1 Hacks #37-44

Be assured that one day, the unthinkable will happen. Hard drives wear. Tapes stretch and break. You might even accidentally pass the wrong switch to a command (or be in the wrong directory, or on the wrong machine) and suddenly find yourself cursing at having hit the Enter key, as your data evaporates into the ether. It is at these moments that you learn the value of a properly designed and executed backup solution.

While we can get you started with some interesting approaches to backing up your data, this section is by no means comprehensive. As a systems administrator, you should design a backup plan that fits the needs of your organization, implement the plan, and continually revise it as necessary as time goes on. Definitely do not assume that just because you set up a cron job to run a backup that the backups themselves are good (or even that the job itself is running properly). Watch your logs. Buy new backup media before the old media develops problems. Make it a policy to test your backups by doing a full restore from backup as often as you deem necessary to sleep well at night. And even then, consider keeping another copy of your data, off-site if need be. For an extremely detailed look at everything that goes into building a secure data backup policy, be sure to check out Unix Backups & Recovery by W. Curtis Preston (O'Reilly).

In this section, we'll take a look at some methods for keeping copies of your data ready for when that day of reckoning comes. Every installation is different, and each site needs its own degree of backup functionality (ranging from weekly differentials to 5-minute snapshots). While we won't try to define the perfect backup policy for your site, we will see some tools you can use to develop your own.