#Mac unmount disk how to
#Mac unmount disk mac os x
#Mac unmount disk install

#Mac unmount disk mac os x

This is a good example of why it’s very valuable to have a bootable USB thumb drive set up with whatever version of Mac OS X is running on your Macs, because without a separate boot drive some of these errors would be unresolvable. The above steps did the trick and everything was working again as expected. I ran into this twice recently, first when attempting to modify partitions on a drive, which came right along with a separate “ partition failed” error, and again was triggered when attempting to format those partitions. Now perform the original task that threw the “Couldn’t Unmount” error.Go to “First Aid” and verify the disk, then repair if needed.At the boot menu, choose “Disk Utility” (if using an Installer disk, pull down the “Utilities” menu to access Disk Utility).Hold down the OPTION key during boot, then select the attached boot drive (typically has an orange icon at the boot menu).Attach the USB boot drive to the Mac and reboot.You will need any Mac OS X boot drive to complete this task, I used a Mavericks boot installer drive for this purpose but others should work too, whether they are installation drives or just recovery drives, the important thing is they are bootable and separate from the primary boot disk that stores the installed OS: This is the recommended method because it should always fix the error.

#Mac unmount disk how to

How to Resolve the Unmount Error with a USB Boot Drive We’ll also show you a way to forcibly unmount a disk by command line, though that approach must be used with caution as it can lead to data loss on the drive in question. We’ll cover both with a bit of explanation. This will allow you to fix the problem, regardless of the cause, by one of two means, the first is a sure-thing to fix the issue, while the other only works sometimes. For the boot drive, it shouldn’t matter which version of Mac OS X it’s for (assuming 10.7, 10.8, 10.9, 10.10, 10.12, 10.13, 10.14, etc at least), the only requirement is that it has Disk Utility – which they all do. For the former situation where the boot drive is being modified, the easiest solution is to boot from another drive and run Disk Utility from there instead. I suggest using Ethernet if possibleīecause it is three times faster than wireless.Typically the “Couldn’t Unmount Disk” error pops up when the currently boot drive is being modified, or if a disk was trying to be erased you may find the erase failed with a couldn’t unmount disk error. Note : You will need an active Internet connection.

#Mac unmount disk install

Reinstall Lion/Mountain Lion, Mavericks : Select Reinstall Lion/Mountain Lion, Mavericks and click on the Install button. The Erase button and wait until the process has completed. The Security button and set the ZeroData option to one-pass. Set the format type to Mac OS Extended (Journaled.) Optionally, click on

Click on the Erase tab in the DU main window.ģ. After DU loads select your startup volume (usually Macintosh HD) from the Select Disk Utility from the main menu and click on the Continue button.Ģ. Install or Reinstall Mavericks, Lion/Mountain Lion from Scratchīe sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.ġ.

This should unmount the drive so you can now do this: For a single drive system this will probably be /dev/disk0. You should also see the name of the disk such as 'Macintosh HD.' Note down the disk identifier. If will look like /dev/diskn/ where 'n' is an integer starting at 0. From the listing look on the left column for your disk identifier. If you are, then you neeed to do the following: Are you booted from the Recovery HD partition? If not, then you need to first boot from the Recovery HD before you can erase the Macintosh HD.