Absolute OpenBSD, 2nd Edition

Backing Up to the /altroot Partition

You can lose most of your partitions and still hope to recover the rest of the system. If you lose your root filesystem, however, recovery becomes a much more difficult task. While you could back up critical files from /etc and use them to restore your system, OpenBSD provides the /altroot partition as an easy way to automatically duplicate the root partition on a second disk.

An emergency root partition on a second disk gives you an easier path to recovery in the event of a disk failure. Booting to the second disk lets you pull any data off that disk, and possibly even from undamaged partitions on the first disk, before replacing the failed disk. There’s no reason to back up your root partition to the same ...