Restoring from Crashplan with a different key
I’ve just attempted to restore a very old Crashplan backup from an external drive. Since this backup is a few months old, it was done before I had a custom key configured for my backups, and hence is inconsistent with Crashplan’s current configuration.
Crashplan warns repeatedly that you can only have custom keys on or off – you can’t have a mix for your account. They also warn that if you change the encryption configuration, it will wipe all previous backups and start again.
So – when I attached the old backup folder, how did Crashplan react?
Figure 1: Custom key selected
First – since Crashplan has a custom key configured for my machine, it tried using that key on my old (non-custom-key) backup, and failed. Evidently it realised that the encryption method had changed, so it apparently renamed the old backup with an OLDKEY suffix before it did anything else.
Figure 2: The OLDKEY suffix for the old backup folder
Then – it started a new backup on the backup file!
This is one problem with Crashplan – you can’t attach an old backup as just for restoration. You attach a folder, and then Crashplan will use that for both restoration and future backups! When you attach a folder as a destination (which you need to do even if only to restore from), then Crashplan will add it to all the backup sets (if you have more than one), and start a new backup to it.
So – my PC saw that there was a backup there already under the same UID, but it didn’t have the key. It renamed that folder, then started a new, blank backup.
I now need to figure out what to do here. I can’t remove the custom key from the UI with uninstalling or resetting the configuration. And if I do THAT, it may wipe all other backups where I do have the custom key, including my cloud backup.
I’ve emailed Crashplan support, so let’s see what I can do here.