[Tutorial] Repairing disk and file system issues in OS X

Disk Utility

With OS X El Capitan, Apple has finally fixed the disk permission issues that many Mac users are familiar with. On top of that, the company completely redesigned the Disk Utility app in order to simplify it for everyone. And though you no longer have to repair disk permissions, you might still run into other disk and file system issues. Today, we will look at the various tools found in OS X that can help you fix such issues. You should try the tools in the exact listed order because you may not even need to go further than Disk Utility for simple errors.

Disk Utility’s First Aid

Your first step should always be to perform a disk health check with the help of the First Aid feature of Disk Utility. Launch Disk Utility from the Utilities folder or from Spotlight (Command + Space). Once it is open, select the disk or partition you want to check. The system partition is “Macintosh HD”, at least when you are using the default settings. After selecting the disk or partition, click on the “First Aid” button at the top and confirm the pop-up by clicking on the “Run” button.

Disk Utility First Aid

If Disk Utility discovers any issues, it will attempt to fix them automatically. Clicking on “Show Details” will let you peek inside the process and see what is happening. In El Capitan, the app is noticeably faster but it might still take a while. When it is over, First Aid will tell you whether everything is alright or not though simple errors will be fixed on the spot.

Safe Mode

Safe Mode, or Safe Boot, allows OS X users to test for problems on their Macs but it can also be used for other purposes. When a Mac boots up in Safe Mode, OS X runs an automatic startup check tool that can easily fix issues as it is not restricted by anything. The tool runs before you are logged in the system so all you have to do is wait until OS X boots into the desktop and then you can restart your Mac normally. To enter Safe Boot, restart your Mac and hold the Shift button while it is booting up.

First Aid in Recovery Mode

I mentioned before that Disk Utility attempts to apply available fixes automatically but that does not mean it always succeeds. One of the reasons why a fix might fail is that Disk Utility might not be able to alter system files while you are running OS X in its normal mode. Because of that, running First Aid in Recovery Mode might allow the tool to apply additional fixes so that it can alter anything it wants. In order to boot into Recovery Mode, restart your Mac and hold the Command + R keys together. Once you see a progress bar, feel free to let the keys go as the Mac will continue on Recovery Mode. After that, just run First Aid exactly like before and hope for the best.

Single-User Mode and fsck

Should all of the above solutions fail to help with your issues, it is time to boot into Single-User Mode and run fsck, the file system consistency check tool. To run your Mac in Single-User Mode, restart it and press the Command + S keys. The mode features a text terminal where you will have to type the following command and press Enter:

/sbin/fsck –fy

If everything is okay, the tool will display a message saying that volume X appears to be OK. If the tool found and fixed an issue, it will say that the file system was modified. In case this happens, it is recommended that you run the test again and again until you get the message that the volume is OK. The reason for running the tool again is that it may find additional issues as it can only deal with a handful at a time. When you are done, simply type reboot into the Terminal and your Mac should boot up normally.