In the old days of the Classic Mac OS, whenever something went wrong, the standard fix was to rebuild the desktop, check the hard drive with Apple’s disk repair application, and restart. That was the beginning and end of it, even if none of those remedies had anything to do with the problem.

Indeed, I once got involved in a heated exchange with a forum helper on AOL who kept repeating this silly mantra even for issues that could not possibly be repaired in this fashion.

Now the promise of Mac OS X was that its Unix foundation would rid Mac users of extension conflicts, desktop rebuilding and other irritating rituals and usher in a new era of speed and stability.

Well, the truth is that we didn’t get the speed at first, but stability was somewhat better, though never perfect. Applications would still crash, only the event would rarely force you to restart. There was no desktop to rebuild, but the world of Unix brought its own nasty complications, the most prominent of which is permissions.

Now giving a file read and write access was a part of the Classic Mac OS too, but Unix refines the process, and since application and system files are routinely made up of tens of thousands or hundreds of thousands of separate files, there’s a whole lot of potential mischief that can occur.

As a result, Apple added a Repair Disk Permissions feature to its Disk Utility to address the problem, although in a very incomplete fashion. It relies on the contents of a folder called Receipts that provides an application and the operating system’s “bill of materials” that catalogs the files and the permissions that apply to those files. If you mistakenly delete those receipt files, unfortunately, or they aren’t present for any other reason, the repair disk function will bypass those apps.

Now wrong permissions may mean that a file won’t open, can’t be properly modified, or any combination of mistakes that might cause erratic system behavior or an application crash. At the very least, the repair process shouldn’t make things worse, so even if it does nothing I suppose it’s worth a try.

However, I can safely tell you that I’ve had maybe one or two problems that can be blamed on permissions issues since I started using Mac OS X, and that started with the original Public Beta in September 2000. Moreover, it’s not that I’m necessarily a shrinking violet when it comes to playing with the system, upgrading early and often and acquiring new systems to test and deploy for my daily work.

More to the point, the most serious of those permissions issues, involving the inability to launch Parallels Desktop 5 on a Mac Pro, was not resolved by Repair Disk Permissions. It required a Terminal command that accomplished a similar purpose, one fed to me by the support people at Parallels. There’s no point even in mentioning the specific command, since it related to a single file listed in my Mac’s crash log. The chances that anyone else would be impacted by the same permissions irregularity are slim to none.

Unfortunately, some Mac troubleshooting resources have taken to making disk permissions repair the prime preventive maintenance procedure before installing software, after installing software, or when you have nothing better to do with your time but watch it happen.

This isn’t to say that the effect is entirely placebo. As I said, there may be times when permissions issues are truly responsible for your grief, but it happens so rarely that you shouldn’t concern yourself about it. Mac application crashes are far more often caused by basic incompatibilities with your OS or a system enhancement or perhaps a damaged preference file. Indeed, repeated crashes often call for just removing that preference file and seeing if things are fixed. Sure, some of your custom settings may disappear when you dump that file, but at least your application will run again.

Now as far as checking the hard drive, well drive directory corruption can occur, though not nearly as often as it did back in the days of the Classic Mac OS. Apple’s Disk Utility, however, limits you to a Verify Disk function when you want to check the startup disk. However, checking the drive can be forced in Snow Leopard by restarting and holding down the Shift key until you see a white screen and a progress bar.

But outright hard drive failures are quite possible. Indeed, it’s fair to say that most of you will confront a hard drive failure at one time or another during the course of working on your Mac, or any personal computer for that matter. Hard drives remain extremely fragile, and that argues all over again for the need to set up a routine for regular and recent backups in case something goes wrong. Product warranties won’t help beyond replacing a failed drive. Lost data remains lost unless you pay a ton of cash to a drive recovery lab.

So checking your hard drive and doing regular backups are probably the two most important troubleshooting steps you can take. As far as the Repair Disk Permissions function is concerned, I usually have better things to do.

This article was posted on Monday, December 28th, 2009 at 6:00 PM and is filed under News and tagged with: Apple, Classic Mac Os, Disk Utility, File system permissions, Mac, Mac Os, Mac Os X, Mac Pro, Macintosh, Operating System, Parallels, Public Beta, Repair Disk Permissions, snow leopard, Terminal, Unix, Verify Disk.