To boot from the Recovery Partition, restart your Mac and hold down the Option key. Fortunately for Mac users, there’s a built-in “boot disk” in the guise of the Recovery Partition.

If First Aid and the Live Verification process indicate that repairs are required on a volume, it’s time to boot from another disk drive and then run Disk Utility again. Finally, an alert message that says “Incorrect size for file temp” is no cause for alarm. In addition, you may not be able to interrupt the Live Verification through First Aid, so it’s best to let it continue to run until completed. If you run First Aid on a volume that is not journaled, Disk Utility responds with an error message saying “ERROR: could not freeze volume (Operation not supported). Note that the Live Verification process only works on volumes that have been formatted as “Mac OS Extended (Journaled)”. We’ll cover that in the next section of this post. To repair a disk, it’s necessary to boot from another drive, then run Disk Utility again. The process usually runs quickly, taking only a few minutes to verify a large (2 TB) boot drive. You’ll get a notification that the First Aid process is complete (see image below), with either a green check mark indicating that everything appears to be OK or a red X indicating that there are some issues that need to be repaired. Disk Utility informs you of what’s about to happen, specifically noting that apps will become unresponsive during the tests.Ĭlick the blue Continue button, and Disk Utility begins to perform its battery of tests on the hard drive. Disk Utility responds by stating what it’s about to do:Ĭlick the blue Run button to begin the process of verifying the disk. To verify a disk, simply launch Disk Utility (found in Applications > Utilities), click on the drive volume you wish to check, then click on the First Aid button in the Disk Utility toolbar. It does this by “freezing” the volume, so while you’re running the verification tests you may find that your Mac becomes slow or unresponsive. This means that Disk Utility can check the status of a disk, its catalog file, multi-linked files, catalog hierarchy and more the Mac needing to be started up with another disk drive. Verifying a disk subjects it to a series of checks, all of which are done through a process called “Live Verification”.

An external device doesn’t work properly.

Some of the issues you might encounter that indicate a disk that might need repair:

This can be useful if you’re running into odd issues with a Mac, so we’ll take a look at the process of verifying and repairing disks with macOS Sierra’s Disk Utility. The updated app now presents a streamlined appearance while retaining all of its former functionality, and it’s still useful for verifying or repairing disks. One of the old Mac OS X utilities, Disk Utility, has received a makeover in macOS Sierra.

Mac os disk utility