BackingUpToOsx

Some things to watch out for when using an OS X machine as a destination for rdiff-backup.

Backing up to an external HFS+ volume*: by default, OS X adds a flag "Ignore permissions on this volume" to mounted external drives. I recommend disabling it. You can see this flag via "Get Info" on the volume from the Finder. Not sure if it is accessible via hdiutil. This means that the filesystem will ignore ownership and group ownership. Not a huge problem if you are restoring with rdiff-backup since it stores metadata in a separate place, but you'll lose expected behavior from cp(1) and other standard utilities.

Also, watch out for newly formatted drives. OS X slaps "unknown" group ownership on a new volume, which will break your backup if you have any source directories with the set-group-id bit. To get around this, just make sure that the root directory of your backups is in the same group as the user running the backups. Any newly created files and directories below it will have the correct group ownership.