Problems with OS X? Have you repaired your permissions?

Funny things, those permissions.  Similar to the Registry of Windows in a couple of ways.  If it gets out of whack, your computer acts bizarre, or just doesn’t act at all.  Also, if you install and remove programs frequently, the likelihood of your registry (in OS X’s case–permissions) have a greater chance of getting screwed up.  The similarity really stops there.

Permissions in OS X are the default values for the system’s read/write/execute access, meaning who has “permission” to read a file, write to a file, and/or make it run.  If these permissions somehow get incorrectly set, you as a user of the computer may run into problems trying to perform one of those actions.

Lots of things can happen when your permissions get messed up.  Some programs, like iTunes, may not authorize to your account.  Sometimes disks or drives won’t mount.  Some programs may not even start, let alone give you an error.  The permissions set up on OS X can easily be repaired, however, so don’t panic.

It is always a good idea after installing or removing a program to repair your permissions with OS X’s built in Disk Utility application; it’s found in /Applications/Utilities/Disk Utility (this is true since OS 10.2, Jaguar.)  For the directorily challenged:

Disk Utility on Hard Disk

Disk Utility on Hard Disk

Once you have found it, open it up and select your hard drive on the left.  Then at the bottom of the page, click “Repair Disk Permissions”.  This may take a little while if you’ve never done it, but usually less than 10 minutes in my experience (even on my PPC G4.)

Here are screen shots before and after on my MacBook Pro:

Disk Utility "First Aid" Tab

Disk Utility "First Aid" Tab

Disk Utility Repair Complete

Disk Utility Repair Complete

This repair took 2m:34s to complete, on my 2.4Ghz Mid-2008 MacBook Pro, 4GB of RAM.  Not too bad at all, and my permissions aren’t in that bad of shape.  You will notice there are two things in the list, and they will not be repaired.  When this happens, it is always a good idea to check out Apple’s Knowledge Base , if for nothing else than peace of mind.

Every couple months or so, for an average web surfer/emailer, it’s probably a good idea to run the Disk Utility found on your installation disks (assuming they are the version of OS X you have installed, of course.)  This is especially helpful to have if you run into serious problems, as you don’t need to rely on the hard disk to boot in order to run your permissions check.  If it is that bad, you may want to Verify the disk as well, as that checks the actual drive itself for errors, not just a file structure problem.