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What Does Disk Repair on Mac Do and How It Improves Performance?

05.01.2018

Users of Mac OS X have two major utilities to verify and repair hard disks or their MacBook Air/Pro and iMac: Disk Utility and fsck.

The Terminal-savvy Mac owners will choose in favor of the command-line fsck utility. Meanwhile, most users will launch Disk Utility if their computer won’t start properly. So, why do you need to repair your Mac’s hard disk?

disk repair on mac

If your machine has sustained improper shutdowns, unexpected power cuts or system crashes, it may experience the system errors or disk directory deprecation. Fixing these errors is important to ensure your Mac’s smooth performance. Perform a thorough disk check in case any of the below symptoms become evident:

  • if your Mac has a strange behavior after sustaining a power cut or a hard restart;
  • if the message saying ‘file system dirty, run fsck’ appears in the middle of Mac’s startup;
  • if your Mac boots up but freezes before making it to the login screen;
  • if your Mac loads the login screen but fails to load the Desktop.

It’s worth running periodic disk checks as a part of maintenance routine before installing the operating system and updates, software, or as a preventative measure.

How to Use Mac Disk Repair Utility?

If Mac OS X startup has failed, running risk repair is the best solution for bringing your computer back to life. However, on macOS Sierra/High Sierra, you can run a disk check for errors:

  1. Go to Applications -> Utilities -> Disk Utility.
  2. Click the First Aid tab -> click the Run button.

click run button

Follow these steps to fix corruption of the directory on your system's startup disk:

  1. Launch Disk Utility, then select Mac OS X startup disk in the left sidebar.
  2. Open the First Aid tab -> press button Repair Disk to launch the disk repair process.
  3. Follow the messages that show up during the disk repair process.
  4. When disk repair is over, confirm if it has succeeded.

Note: running disk repair on a startup disk won’t work, so you will have to boot up from your installation disk or another drive.

The Disk Utility messages will read as one of the following:

  • No repairs were necessary;
  • The volume has been repaired;
  • Repaired the disk.

On the latest macOS versions, the Disk Utility will report something like your disk is OK or ‘your disk has been repaired.’ If disk repair fails, the message will read ‘The underlying task reported failure.’

How to Repair Mac Disk Permissions?

When running a disk repair procedure on your MacBook Air/Pro or iMac, repairing disk permissions is also a good idea. The above applies to the Mac OS X versions before El Capitan. As for macOS Sierra and High Sierra, these OS versions no longer include disk permissions repair.

  1. Go back to the Disk Utility home screen and select the volume you want to repair disk permissions.
  2. It is possible to verify and check disk permissions by clicking the corresponding options
  3. Repairing disk permissions is especially important if the disk check procedure has sustained a failure. The volume needs repair if you get the following errors:

Error: The underlying task reported failure on exit.
Error Code -9972.
Failed to repair the disk.

  1. Alternatively, it is possible to repair disk permissions by running a special Terminal command: $ sudo diskutil repairPermissions /

Disk permissions repair can take some time depending on how fast and capacious your hard drive is.

Running sequential permissions check on several hard disks or volumes is possible. The procedure is over when the ‘Permissions repair complete’ message appears.

permissions repair complete’

What to Do If Disk Utility Fails?

In the event the Disk Utility failed to repair the directory corruption it has discovered, follow the below troubleshooting instructions:

  • If the following error messages: ‘Underlying task reported failure’ or error code -9972 persist, consult with the Apple support community.
  • Repair Disk will not have any effect on severe directory corruption. However, it’s worth trying third-party disk utilities like Micromat TechTool Pro or Alsoft DiskWarrior.
  • Make sure you have the latest disk utility version installed on your Mac before trying to repair a disk or volume.
  • If none of the troubleshooting techniques help Mac OS X has another utility – ‘verify.’ With its help, one can check the disk for possible problems.

To run the verify utility on El Capitan, type in the following command in the Terminal app:

$ sudo /usr/libexec/repair_packages --verify --standard-pkgs /

In case the utility finds issues, run the repair utility in Terminal to eliminate the problem:

$ sudo /usr/libexec/repair_packages --repair --standard-pkgs --volume /

Bottom Line

Whenever your Macintosh HD corrupt needs to be repaired, Disk Utility can help you out. It checks the startup disk and other volumes on your Mac for errors and fixes them on time. Mac OS X El Capitan and earlier OS X versions verifying and repairing disk permissions using Disk Utility or Terminal commands. In macOS Sierra and High Sierra, the Disk Utility has a slightly reduced functionality. The latest Mac OS versions can repair disk permissions automatically.


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