(You don’t have access to the Disk Utility User Guide when you restart your computer in the next step.) In the Disk Utility User Guide window, click the Share button, then choose Print. Choose Apple menu Restart. After your Mac restarts (some Mac computers play a startup sound), press and hold the Command and R keys until the Apple logo appears, then release the keys. Click Disk Utility, then click Continue. Choose View Show All Devices.
This guide will list some common macOS Sierra problems and show you how to quickly fix them. Here's what you need to do if your Mac is running slowly, freezing, or crashing while you're installing Sierra: 1. Prior to installing Sierra, uninstall or disable antivirus utilities on your computer. One of the old Mac OS X utilities, Disk Utility, has received a makeover in macOS Sierra. The updated app now presents a streamlined appearance while retaining Your source for expert tips, special deals, commentary, reviews, and the latest tech news.
In the sidebar, select the disk you want to repair. Click the First Aid button. If Disk Utility tells you the disk is about to fail, and replace the disk. You can’t repair it. Otherwise, continue to the next step. If Disk Utility reports that the disk appears to be OK or has been repaired, you’re done. You can click Show Details to see more information about the repairs.
Otherwise, you may need to do one of the following. If Disk Utility reports “overlapped extent allocation” errors, two or more files occupy the same space on your disk, and at least one of them is likely to be corrupted. You need to check each file in the list of affected files. Most of the files in the list have aliases in a DamagedFiles folder at the top level of your disk. If you can replace a file or re-create it, delete it.
If it contains information you need, open it and examine its data to make sure it hasn’t been corrupted. If Disk Utility can’t repair your disk or it reports “The underlying task reported failure,” try to repair the disk or partition again. If that doesn’t work, back up as much of your data as possible, reformat the disk, reinstall macOS, then restore your backed-up data. If your Mac has a Fusion Drive and you see a flashing question mark or alert, see the troubleshooting section of the Apple Support article. If you continue to have problems with your disk or it can’t be repaired, it may be physically damaged and need to be replaced. For information about servicing your Mac, see.