Verifying backups

I have already spoken about backups at least twice in this book and this will be the last time I promise. Create your backup scripts and make sure they run when they are supposed to. But one thing I have not talked about yet is verification of the backups. You might have 10 teraquads of backups lying around somewhere, but do they actually work? When was the last time you checked?

When using the tar command it will report at the end of the run if it encountered any issues making the archive. In general if it doesn't show anything amiss the backup is probably good. Using tar with the -t (tell) option, or actually extracting it on the local or remote machine, is also a good way to determine if the archive was made successfully.

Note

Note: A somewhat common mistake when using tar is to include a file in the backup that is currently being updated.

Here is a rather obvious example:

guest1 /home # tar cvzf guest1.gz guest1/ | tee /home/guest1/temp/mainlogs`date '+%Y%m%d'`.gz

The tar...