Using the Disk Utility for Macs

Using the Disk Utility for Macs

Hidden in the “Utilities” folder, the Disk utility with its “First Aid” function can be used to check if a disk is damaged and repair it. […]

Whether you need to better organize your hard drive or fix problems with it, Disk Utility is the right tool for this task. The disk utility built into macOS is located in the “Utilities” folder, which is located in the “Applications” folder. However, it is easy to find it through Spotlight by pressing Command+Spacebar and then simply typing “Disk Utility”.

The tool displays details and a diagram of your disk configuration, which shows the total capacity, as well as the occupied and free space and the various volumes.

Over the years, the Disk utility has been revised several times, so the options may be slightly different depending on the version of macOS you are using. For example, in Mac OS X El Capitan, the disk utility has been redesigned and many of the features have been further developed or removed.

Also in macOS High Sierra there have been a few changes thanks to the new file format that Apple has introduced: APFS. And with the introduction of Catalina, a new Macintosh HD data volume was displayed next to a read-only Macintosh HD system volume.

What should I use the Disk utility for?

  • Delete, format or manage internal hard drives and external storage devices.
  • Diagnose and fix problems with a hard drive or damaged volumes.
  • Delete, format or partition a hard disk or volume.
  • To encrypt storage devices or to add a password to protect a drive.
  • To mount, unmount or eject a data carrier.
  • To change the file system – for example, to enable or disable journaling.
  • Working with RAID sets. Combining multiple hard drives into a RAID set that behaves like a single hard drive can increase performance, reliability, and storage space.
  • Create a disk image of files that you want to move, archive, or back up to another computer.
  • Disk Utility used to be used to check and repair permissions, but since El Capitan this is no longer necessary.

Also, you can use the Disk utility if you have any of the following problems:

  • Your computer won’t boot up.
  • An external device does not work.
  • Your applications will quit unexpectedly.
  • You have a corrupted file.
  • You believe that there is a problem with your startup disk.
  • You need to repair a damaged hard drive.

Below we will show you how to perform the most common tasks of the disk utility.

The Disk utility contains options for creating a new volume or partition, deleting, restoring or unmounting. It can also perform a first aid for your hard drive. (Source: Foundry)

How to find out if your hard drive is faulty or damaged

If you think that there is a problem with the drive in your Mac or an external storage device, you can use the first aid function of the Disk utility to check.

This function of the disk utility performs various checks and repairs the disk if it detects a problem.

Note that you cannot use first aid to repair your boot drive while it is running the operating system. Next, we will show you how to do this.

How to run the First Aid program on your Mac or on an external drive to check if there is a problem with the hard drive:

  • Open the Disk utility.
  • Select the device you are having problems with in the sidebar. Click Show All Devices (in the drop-down list above View) if you don’t see it.
  • Click on First Aid.
  • Disk Utility checks the disk for errors and, if necessary, repairs it. Click Run.
  • While Disk Utility is checking the volume, you will not be able to use your Mac – in addition, note that this can take a very long time.

If a problem with the disk is found, the Disk utility will try to repair it.

If Disk Utility is unable to repair the drive or believes that the drive is about to fail, you will be warned. If this is the case, you should back up your data before it’s too late.

If Disk Utility reports that the disk is OK, it means that there is no problem with the disk.

How to Repair Your Startup Disk with Disk Utility

You can perform the first aid for your boot drive as described above, but if the Disk utility finds errors, it will not try to fix them.

If you need to repair the boot drive of your Mac (the boot volume), this is not possible because Disk Utility cannot repair the mounted volume (the volume from which everything is running).

In this case, you need to boot your Mac in Recovery mode and repair the hard drive from there. In this way, everything can run from the recovery disk created when installing macOS.

The method to access Recovery mode depends on your Mac:

  • If you have an M1 series Mac, turn off the Mac and then press and hold the Power button when booting up.
  • If you have an Intel Mac, restart your Mac and press and hold Command-R on the keyboard.

How to repair your startup disk:

  • Start in recovery mode by following the steps above.
  • Once your Mac has booted up in Recovery mode, you will see a screen with utilities. Select the Disk utility.
  • Select the hard drive you want to repair from the menu and click First Aid.
  • As described above, the Disk utility performs its checks and, if possible, tries to repair the disk.
  • The repair process may take a while.

You will see details of everything that has been checked. If repairs were necessary, you will also receive information about what was necessary for this.

*As editor of Macworld U.K. since 2008, Karen has worked on both sides of the Apple border. Before joining Macworld U.K., she worked at Apple’s PR agency for several years.

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