I had the unfortunate event of having to send my MacBook Pro into Apple for some repairs. The machine came back working fine, however there was something odd going on with TimeMachine – it wanted to do a full backup of my disk. Odd, considering I keep it plugged-in all the time when I’m at my office desk. I tried re-selecting the disk, but that didn’t work. Clearly this would require some detective sleuthing on my part.
There are a couple points you need to know.
* First of all, check the Apple Support forums. They have some good information on there, but most of it is pretty basic. Start there then move on if you haven’t quickly solved your problem.
* Time Machine disks know your computer by the MAC address. This was the root of my problem – it seems my mac address had changed (new logic board?).
* I eventually found my solution at MacOSXHints.com, however I had to do a little more work to actually get everything working. See below.
What made this a step more difficult was that the MacOSXHints solution didn’t quite work, however one reader commented on a unique situation that resembled mine. in the /Volumes/TimeMachine/Backups.backupdb directory there were MyComputerName and “MyComputerName 2″ directories. The former had all my backups in there, the latter didn’t have any completed backups and showed a file creation time of today, not the last time I ran a backup. So with the ACL turned off (see the directions) I removed the “MyMachineName 2″ directory (mind you – I had already completed all the steps on MacOSXHints.com before trying this. It might be important). It worked.
YMMV but hopefully this will work for you.