In a previous post, we showed how to use the Disk Utility application to repair disk permissions. This was sometimes useful in fixing random issues on a Mac, like slow operation, crashing applications, and other odd behavior. Much to the surprise of many, the latest version of OS X, El Capitan, actually removed that functionality from the Disk Utility, and I have been asked many times lately if there is another technique that can provide the same results.
Fortunately, the answer is yes. In fact, this new technique can yield even better results than the Disk Utility was able to achieve. In addition, it’s quite a bit simpler: all you need to do is boot into Safe Mode.
Safe Mode is generally used for fixing problems when the computer won’t boot at all. It starts up the Mac, but disables a lot of animations, plugins, and other extensions that could be keeping it from starting normally, allowing for troubleshooting and repair.
When a Mac is in the process of starting up in Safe Mode, it runs several diagnostic and repair functions in the background, including repairing disk permissions. This means that sometimes just booting into Safe Mode and then restarting the computer normally is enough to fix those same issues that used to be fixed with the Disk Utility.
To do this, start by shutting down the Mac. Then, when the computer is completely off, hold down the Shift key and turn it back on. Keep holding the Shift key until you see the Apple logo on the screen with a status bar moving underneath it. Because of the tools that are running during the boot into Safe Mode, it will probably take longer to start up the Mac than it normally does. Once it is fully loaded, log in if necessary, then restart the computer normally.
This will not always fix the issue, but it is a terrific and easy place to start.
Jason Merrill, Mac & iOS Consultant