I have a bunch of hosts in my backuppc configuration using Tar. I removed the SSH command because they all point to the local host IP (I use hostnames to logically separate backups).
One of my backups kept failing with this error:

“Tar exited with error 512 ()”

I Googled a bit and found it could relate to permission errors. This made sense, but the perms were all the same as another backup I have…which completes successfully.

I tried to find out more about GNU Tar and the errors it can produce, but the newsgroup posts I found were not very helpful (I wonder, is there any official documentation for these errors?). What I found was that Tar will exit with error 512 if there is a permission error OR a failure in following a symlink. I had some dead symlinks that were breaking the BackupPC tar command. Delete those links and all is good!