Mac – How to rescue light red Time Machine backups

By default, Time Machine keeps the following backups:

• Hourly for the current day
• Daily for the past month
• Weekly for all the other months

If there's space constraints then Time Machine will start to delete the backups, but otherwise it keeps them for as long as possible.

To get to the individual photos you will have to have iPhoto as the active window when you activate Time Machine from the menu bar. This lets you go back and see all of the photos. If you did it from the Finder it's more complex because iPhoto bundles its whole library into one big package.

I haven't found any documentation for this feature yet, so I don't have any specific answers for your questions about interactions with external Time Machine drives.

However, I did do some playing around with the feature while using my laptop on battery. The first thing I noticed is that local snapshots were not enabled by default – for me, at least. I know that because "entering" Time Machine while my backup drive was detached resulted in the usual error message — until I executed the following from a command line:

sudo tmutil enablelocal

After I did this, a hidden volume called MobileBackups was created (in /Volumes) and I was able to "enter" Time Machine. (Perhaps local snapshots weren't enabled on my machine because I have less than 10% free disk space?)

Unfortunately, the feature seems a little half-baked. I tried the following, with pretty unsatisfactory results:

1. Created a new folder, ~/Documents/Test.
2. Forced a new snapshot by running tmutil snapshot.
3. Verified that a new snapshot was created by looking in /Volumes/MobileBackups/Backups.backupdb/hostname/Latests/drivename/Users/myname/Documents.
4. Deleted the Test folder.
5. Entered Time Machine and browsed the backups/snapshots. The Test folder was not there in any of the backups.

Update: I installed Lion on a second Mac, and without any explicit action on my part, this Mac has a MobileBackups volume. And restoring deleted files from a local snapshot works on this Mac.