HOW TO Repair or restore a volume with Disk Utility

1 Mount the drive

Connect the drive you want to repair, launch Disk Utility, and wait for it to appear in the sidebar. If it is greyed out, select it and click Mount in the toolbar. When it mounts, select it or the volume you want to repair.

2 Use First Aid

Once you’ve selected the drive or volume, click First Aid in the toolbar and wait for it to finish, which may take several minutes. Disk Utility will scan the drive looking for problems and fix those it finds, if it is able to.

3 Back up then erase

If First Aid can’t repair the drive, it will tell you. Your best bet now is to back up the data on the drive and then erase it completely. If you can’t recover the data you need, your next step should be a specialist recovery tool or service.

4 Erase options

Once you’ve recovered your data, choose the drive in the sidebar and click Erase. If there’s a Scheme menu, choose GUID Partition Map. Click the Format menu and choose a filesystem format (APFS for recent macOS versions).

5 Erase the volume

Type in a name and then, if it’s a hard drive (rather than an SSD) click Security Options and use the slider to choose how many times the data should be overwritten – the higher the number, the more secure. Click Erase, then Done.

6 Select data volume

As well as repairing an external drive, you can use Disk Utility to repair the special Data volume on your startup disk. This is separate from the system software volume. Click View and then Show Only Volumes or ⌘+1.

7 Repair data volume

You will notice that the sidebar doesn’t now show drives and containers. Click the down arrow next to Macintosh HD. You should see two volumes, select the one called Data. Click First Aid in the Disk Utility toolbar.

8 Restore a volume

Restoring a volume wipes all the data on the target volume and makes a direct copy of the source volume on it. In the sidebar, select the target volume and click Restore in the toolbar or press ⌘+⇧+R.

9 Continue restoring

Next, click the Restore menu and choose the volume you want to restore from. If it doesn’t appear in the menu, make sure it is connected to your Mac and that it is mounted. Click Restore, then click Done to start copying.