Mac OS X: The Missing Manual, Tiger Edition

Fixing the Disk

The beauty of Mac OS X's design is that the operating system itself is frozen in its perfect, pristine state, impervious to conflicting system extensions, clueless Mac users, and other sources of disaster.

That's the theory, anyway. But what happens if something goes wrong with the complex software that operates the hard drive itself?

POWER USERS' CLINIC: Journaling vs.fsck

Mac OS X 10.4 comes with journaling turned on. As noted on Section A.4, journaling means that the Mac keeps a diary about every tiny bit of hard drive activity. In event of a crash or freeze, the Mac knows precisely what was going on at the time, and precisely which files might have been damaged.

In theory, then, you'll never need fsck at all. After all, there's nothing to check. The Mac's journaling software is always on top of things—and, if the journal indicates that there was trouble saving a file, Mac OS X can finish or undo the change.

Even Apple concedes, however, that in the real world, things can still go wrong, even with journaling turned on.

That's why, when you attempt to use fsck as described on these pages, a message will inform you that, hey, you don't need to repair your disk. Thanks to journaling, there's no damage to repair.

If you decide to proceed on the off chance that something's gone wrong behind your journal's back, just use the -f flag to force the disk check, like this: fsck -f.

Note, however, that you may see a series of phony error messages when you do this. If you see any ...