because Spotlight prevents the unmount request). Unmount any volumes on the specified diskĭisk Utility occasionally has problems with unmounting a volume while attempting to erase it (e.g. If your disk is a Fusion device, you may erase the 'container' within it instead. You must select the whole disk to correctly initialize the device. Please pay particular attention to selecting the disk, not one of the volumes on the disk. A startup disk will often include the manufacturer's serial number in the title (e.g. The name of a new disk will often include the manufacturer’s name (e.g.

This disk should not be the same as your startup disk. Before doing anything else in Disk Utility, choose Show All Devices from the View menu, or from the View popup button in Disk Utility's toolbar.Ĭlick to select the disk that you would like to use as the destination for your CCC task. Unfortunately, this hides the devices that you need to select to modify the partitioning of your backup disk. Watch a video of this tutorial on YouTube Show All Devicesĭisk Utility offers a very simplified view of your devices by default. Instructions for Big Sur, Catalina, Mojave, and High Sierra

macOS 10.12 Sierra and OS X 10.11 El Capitan.

macOS 11Big Sur, 10.15 Catalina, 10.14 Mojave, and 10.13 High Sierra.

Choose About This Mac from the Apple menu to determine your current OS, then make a selection below. Learn more about reinstalling m acOS.The remaining steps vary considerably depending on the operating system you are running.

If you want your Mac to start up again from the volume you just you erased, select Reinstall macOS in the utilities window, then click Continue and follow the onscreen instructions.

When done, quit Disk Utility to return to the utilities window.Optional: If you previously used Disk Utility to add internal volumes other than Macintosh HD, you can erase them individually using the same process.If this button isn't shown, click Erase instead. Format: APFS or Mac OS Extended (Journaled), as recommended by Disk Utility.Click the Erase button in the toolbar, then enter the requested details:.Select Macintosh HD in the sidebar of Disk Utility.From the utilities window, select Disk Utility and click Continue.If asked, select a user you know the password for, then enter their administrator password.Start up from macOS Recovery: Turn on your Mac, then immediately press and hold these two keys until you see an Apple logo or other image: Command (⌘) and R.

How to clear your startup disk