But, if you did choose the volume and still failed, you can click View > Show All Devices to display all the drives, then erase the drive itself to see if it succeeds. We recommend you erase the volume but not the entire disk to avoid the 'Secure Disk Erase Failed - Couldn't Unmount Disk' error. Then keep the Scheme as GUID Partition Map.

Name the hard drive (like Macintosh HD), choose APFS for macOS 10.13 or later Mac OS Extended for macOS 10.12 or earlier.

Select Macintosh HD, then click the Erase button.

Ignore this step if your Mac is running macOS Mojave or earlier.

Select Macintosh HD - Data, click the (-) sign, then tap on Delete to confirm the deletion.On the Utilities window, select Disk Utility.Select a language, then your account, and enter the password for it.On an M1 Mac: Turn off your Mac, and press the power button until you see the Options Menu. On an Intel-based Mac: Restart your Mac, then hold Command + R keys until the Apple logo shows up. That's because you can't erase the drive you are currently running from, and you need to boot into Mac Recovery mode to format the Mac startup disk. If you are trying to format the Mac hard drive or its volumes - Macintosh HD and Macintosh HD - Data, you will inevitably see the Erase button grayed out in Disk Utility. How to fix the Erase button grayed out in Mac Disk Utility? How to fix the 'Erase process has failed' error on Mac? What to do when Disk Utility can't erase Macintosh HD? Here, we will discuss solutions to solve these Disk Utility erase errors so you can format the disk.

You may fail to erase APFS volume on your Mac hard drive or an external hard drive when the erase button is grayed out on Mac Disk Utility or when you receive the 'Erase process has failed' error message. What to do when Disk Utility won't let you erase sd card s, USB drives, and other hard drives on Mac?

Could not unmount disk 69888