A Time Machine medley

Leopard's Time Machine, while wonderfully easy to use, is turning out to be surprisingly touchy. The latest news on this front comes from Apple itself, which has posted a note warning that the "time travel" window mightn't show your past backups if your computer's name is wrong. Apple warns that your computer's name (which can be set in your Sharing preferences) should contain only basic alphanumeric characters 0-9 and a-z. Apple also says, "If this is a new Mac, make sure the computer name uses the same as what was used on your previous Mac;" this seems incoherent, since how can it possibly matter whether your computer's name is the same as some other computer? Anyway, the notion that the computer's name can have a bad effect on Time Machine's behavior is very surprising, and suggests a certain lack of planning on Apple's part. This new explanation may clarify Time Machine problems already reported by some of our readers.

In a different note, Apple explains why Time Machine may just stop backing up files suddenly after the backup has reached a certain size. It's because some hard disks have the wrong partition type (they have what's called a master boot record). Before trying to use an external drive for Time Machine backup, you should repartition it, using Apple Partition Map for a PowerPC Mac and GUID partition scheme for an Intel Mac. It is not enough to erase the content of the existing partitions; you need to repartition so that the new partitioning scheme is installed on the disk as a whole.

Then there is the interesting bug reported to us by one of our readers (and easily confirmed by experimentation). You're probably aware that Mail has its own access to Time Machine: if you click the Time Machine icon in the Dock while Mail is frontmost, you get a special Mail "time travel" window. However, if you happen to have used application bindings in Spaces to specify that the Finder should appear only in one particular space, and if you are not in that space at the time you click the Time Machine icon in the Dock, Mail won't be able to get into the "time travel" window: the screen jumps and flickers and the computer appears to be frozen (though you can in fact get out of this state by pressing Esc). This isn't an entirely likely scenario, since confining the Finder to a single space would be a slightly wacky thing to do; but who would have thought that the Finder and Spaces could have an effect on Mail and Time Machine?

Finally, some users are reporting that Time Machine's icon has superimposed itself on the icon of their hard disk in the Finder. The "clock" icon is normal for an external disk that you've designated as the Time Machine backup disk, but apparently some people are seeing this icon for their internal hard drive as well (perhaps this happens, in particular, when the Time Machine backup drive is disconnected?).

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