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In a recent edition of OS X Odyssey, I remarked that most Mac users do very little, if any disk maintenance. No doubt this is partly due to an “if it ain’t broke, don’t fix it” philosophy, which is one that I generally share. It may also be that many Mac users don’t know much about preventative maintenance, and/or don’t have any disk fixing or repair tools other than the ones that ship with the Mac OS.

Back in System 7 days, I discovered that it was prudent to run a disk repair utility about once a week if I had experienced any crashes (if?), but with OS 8.6 and later, I found that crashes were (a) much less frequent, hand (b) rarely caused directory damage. Still, I run Disk Express and Norton Disk Doctor (see below) several times a year to make sure that all is well. It usually is, save for a few minor problems that are easily fixed.

With OS X, there seem to be several schools of thought regarding disk maintenance. Some suggest that Unix is so robust that you can for the most part use it and leave things alone. Others argue that you should run various maintenance and repair routines frequently, using both Apple’s built-in tools and an arsenal of third-party utilities and hacks.

I fall somewhere in the middle. I have neither the time nor the inclination to devote a lot of energy to tweaking and babying my operating system. On the other hand, I’ve discovered that it is prudent to attend to routine OS X maintenance chores in moderation.

One disk maintenance tool you already have as Apple’s bundled disk utility, a freestanding application called Disk First Aid in the Classic OS, and a module of the multi-function Disk Utility in OS X. These are not heavy duty disk repair applications, but if you run them regularly, the theory is that they will fix problems while they are still small, obviating the need for disk repair heavy lifting.

Disk First Aid, the OS Classic version, can run verification of the startup disk, and in some cases repair it without booting from another volume, and indeed will do so automatically after a crash or other improper shut down unless you disable the Check Disk function in a check box in the General Controls control panel. OS X Disk First Aid, on the other hand, requires you to boot from the Mac OS X install CD-ROM in order to verify or repair the OS X startup disk or hard drive partition, which is a pain. I detest booting from CDs. Also note that the most reassurance you’re going to get from Disk First Aid years “Volume [name] appears to be OK.” This is as affirmative as Disk First Aid gets, even on a freshly initialized hard drive.

Among a third-party disk utilities, my favorite is Alsoft’s Disk Warrior, which does just one thing, but does it exceptionally well. Disk Warrior is currently a Classic OS only tool, although I have found that it will happily rebuild an OS X disk or partition’s directory while booted from OS 9 -- just another of the many reasons why dual-booting and partitioned hard drives are something I’m not ready to let go of. An OS X native version of Disk Warrior is under development, but for now, the Classic OS version is all that’s available. You can also run Disk Warrior from its CD, but that presumably will not work on new machines sold after Mr. Jobs polls the plug on dual-booting next month.

Norton Disk Doctor, which is a module of Norton Utilities and Norton SystemWorks, , is probably the best - known third-party disk repair tool. The version of Norton Disk Doctor in Norton utilities 7 is OS X native. Norton Utilities 6 can repair OS X disks when booted from OS 9, but older versions should not be used to repair OS X volumes. Norton Disk Doctor can check and repair damage to your disk’s directories, partition maps, files, and it also checks the hardware media.

Micromat’s Tech Tool Pro 3.0.5 and higher is another OS 9-based disk repair application that can also repair OS X disks. However, Micromat makes a dedicated OS X native disk repair utility called Drive 10 that is advertised as being especially Unix savvy. Both the Norton and Micromat disk utilities are designed to run from their bootable CDs, but the OS 9 versions can also check and repair other (non startup) volumes and partitions when booted from the hard drive.

Another disk check and repair option available in OS X is the command line File System Check Command (fsck). To use it, you need to start up in “single user mode.” As I understand it, fsck a does pretty much the same job as the Disk First Aid function in Disk Utility, but doesn’t require booting from a CD, which is a convenience. In order to run fsck, hold down Command and S while booting or restarting your Mac. Instead of the familiar Aqua startup graphics, what you will see is a black screen with an astonishing amount of scrolling Unix code. This stuff is actually going on under the surface of the pretty Aqua interface all the time, but singleuser mode gives you direct access to it.

After the system completes its startup routines, you will arrive at a command line prompt reading localhost#. You don’t have to log in, which is why this is called “single user mode.”

Now, type fsck -y (make sure to include the space between the k and the -) and press Enter. The system will now administer five sets of tests, after which you will see either:

“The volume [name of “volume] appears to be OK”

or

“File system was modified.”

In the former case, you’re done. Just type reboot, press Return, and you will be returned to be wonderful world of Aqua. In the latter case, you need to run fsck again, and as many times as it takes to get the “Volume.... Okay” message.

A new feature in the OS X 10.2 and later version of Disk Utility is Verify and Repair Disk Permissions buttons.

Apparently, sloppily written software installers have a nasty habit of damaging permissions, and this routine fixes them. It’s probably a worthwhile to do this once in a while -- some suggest that once a week isn’t too often. The first time I ran it (after over a year of OS X use) the repair readout dialog ran 54 lines and 384 words. I don’t bother with running the Verify function. It runs slowly, and you will almost certainly need a Repair run anyway.

Charles W. Moore

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