Creating a Backup Schedule

If your backups are to do you any good, they must exist. It's easy to overlook a backup procedure if it's something you do infrequently or irregularly. Thus, you should create a regular schedule of backups and a routine to implement them. Just how frequently the backups should be performed is up to you. You should consider factors such as the inconvenience of creating the backup (including system or network slowdowns while backing up), your budget for media, and the importance of work lost between the backup and a system failure.

The last factor is arguably the most important, particularly for a large multiuser system or a network. If a single Linux computer functions as a file server for two dozen people who store documents on it daily, a backup that's just one day out of date represents about 200 hours of lost work. On the other hand, a home system with a single user who creates few documents might do well with weekly backups; the number of truly vital files stored on such a system in a week is likely to be small.

Typically, you'll perform a full backup on a system once a week or once a month, and you'll perform incremental or differential backups on a weekly or daily basis. For instance, you might perform a full backup on the first day of each month, an incremental backup every Friday, and a differential backup every other weekday. Such a schedule might require accessing over half a dozen media for a full restore, though. Another plan might involve a full backup every Friday and incremental backups every day. Such a system would require accessing a maximum of two media for a full restore.

Tip Because incremental and differential backups typically consume much less space than do full backups, you can probably fit several of these smaller backups on a single backup medium. For instance, you might need one complete tape for a full backup, but you can fit an entire week's worth of differential backups on one tape. Be sure to consider this fact when purchasing backup media.

Backups are best performed when system resources aren't being heavily used. Typically, this means late at night. Unfortunately, this also means that you're not likely to be physically present when the backup runs. (If it's a home system, you might try initiating a backup when you stop using the computer at night, though.) For this reason, backups are frequently handled via scripts called from cron jobs. You can place such a script in /etc/cron.daily on most distributions, and the system will run it automatically early in the morning. Of course, you must ensure that the backup medium is accessible; if it's not, the backup won't occur. You should also ensure that the backup script generates reasonable error reports in such a situation, and that the cron job mails these reports to your account or otherwise notifies you of the problem.

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