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Essential System Administration, 3rd Edition by Æleen Frisch

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Backing Up Files and Filesystems

Most systems offer a variety of utilities for performing backups, ranging from general-purpose archiving programs like tar and cpio to programs designed for implementing multilevel incremental backup schemes on a per-filesystem basis. When the largest tapes held only a couple hundred megabytes, choosing the right utility for system backups was easy. tar and cpio were used for small and ad hoc backups and other data transfer needs, and the more sophisticated utilities specifically designed for the task were used for system backups, because their specialized abilities—the ability to span tapes and to automatically perform incremental backups—were essential to getting the job done.

This distinction breaks down to a great extent when a single tape can hold gigabytes of data. For example, incrementals are less important when you can fit all the important data on a system onto one or two tapes—and you have the time to do so. Large tapes also make it practical to back up a system in logically grouped chunks of files, which may be spread arbitrarily throughout the physical filesystem. A successful system backup process can be built around whatever utilities make sense for your system.

Note

One dubious piece of advice about backups that is frequently given is that you should limit filesystem size to the maximum backup media capacity available on the system. In this view, multi-tape backup sets are simply too much trouble, and the backup process is simplified ...

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