Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the arrow button below the icon. Select Disk Utility from the list and click on the Continue button. See if this lets you erase the drive. Aug 21, 2017  This is the best way to format an external hard drive for use with a Mac. I use Mac OS Extended Journaled because my hard drive is strictly used with Macs. If you need to use the drive with a.

Disk Utility User Guide

You can unmount a disk set or a member disk if you need to repair it or perform other maintenance.

Unmount a disk set

1. Minecraft java 11. In the Disk Utility app on your Mac, select the disk set that you want to unmount in the sidebar.

2. Click the Unmount button in the toolbar or beside the disk set name.

After unmounting a disk set, you can disconnect the disk members of the set from your computer.

Unmount a disk member of a set

1. In the Disk Utility app on your Mac, select the disk set that you want to unmount in the sidebar.

2. Click the Unmount button in the toolbar or beside the disk set name.

3. Disconnect the disk member that you want to unmount.

If you unmount and disconnect a disk and then reconnect the disk later, Disk Utility rebuilds the disk member automatically if you selected “Automatically rebuild” when creating the disk set. If you need to rebuild the disk manually, see Repair a disk in a disk set.