I followed the instructions in Restore Macintosh HD to its original partition configuration to delete the Core Storage Logical Volume Group via terminal while pressing Cmd+R during startup. These are the functions I used in terminal:

diskutil cs list
diskutil cs delete <Logical Volume Group UUID>

Now I cannot resize the partition via Disk Utility. The post mentioned that a red error message would appear when selecting the drive, but that didn't happen. I'm stuck!

When I try entering "diskutil cs list" in Terminal it returns:

No CoreStorage logical volume groups found.

These are screenshots from the errors in Disk Utility:

Disk Utility

After resizing the top partition by dragging down and clicking "Apply", an error message prompts: "Couldn't unmount disk". Also happens after I repair the disk.

Couldn't unmount disk.

When restarting the computer, a grey screen with error icon appears.

Error icon on boot

  • Rule 1 - don't try to repartition your boot drive, whilst you're booted from it.
    – Tetsujin
    Commented Jan 22, 2015 at 8:38
  • 1
    Tetsujin: Instead of rephrasing the obvious lesson learned, do you have a solution?
    – chrisshon
    Commented Jan 22, 2015 at 20:16
  • Try picking through apple.stackexchange.com/questions/154964/… or go for Internet Recovery
    – Tetsujin
    Commented Jan 22, 2015 at 20:24
  • @chrisshon You can't expect two red signed hdds after deleting the CoreStorage volume if you don't have an original or DIY-Fusion drive. Is your volume empty or does it contain some data or a system?
    – klanomath
    Commented Jan 22, 2015 at 21:32
  • 1
    @Tetsujin I was going through the link you posted, but when trying to create a disk image of 'Recovery HD' I get an error prompt: "The disk "Recovery HD" could not be unmounted. Please check that all applications and files are closed on this disk." Also - When I enter "diskutil cs list" in terminal it returns "No CoreStorage" logical volume groups found."
    – chrisshon
    Commented Jan 22, 2015 at 22:36

3 Answers 3


I recommend:

  1. Restart to Internet Recovery Mode by pressing alt cmd R at startup.
    The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated.
    On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot into the recovery netboot image which is loaded from an apple server.
  2. In the opening window choose 'Disk Utility' and erase/format/partition the internal drive. Choose '1 Partition' 'Mac OS Extended (Journaled)' and GUID partition table (available with the 'Option' button). Quit 'Disk Utility'.
  3. Plug in your Time Machine backup drive.
  4. Start 'Restore From Time Machine Backup' and recover your old system

Instead of recovering your old system after step 2 you may install a new system by clicking on 'Reinstall OS X' and continue later with the steps 3. & 4. and recover your personal data only:

reinstall OS X

  • I don't have time machine Commented Nov 17, 2015 at 9:51

Boot into Recovery Mode (hold down Command+R on startup) . Restore your computer or try to partion it through the Recovery HD.

  • 1
    When I try to Restore, it says that the Recovery HD is locked. How would I partition through Recovery HD?
    – chrisshon
    Commented Jan 21, 2015 at 22:01

Perform the following steps:

  1. Hold down Command + r on Apple keyboard or Window + r on a PC keyboard.

  2. Format or fix the partition.

Once complete, you will be able to download the OS that came installed on your computer.

  • So...given that the OP is already using recovery mode in an attempt to fix the problem, how does this add to the available solutions?
    – Allan
    Commented Apr 12, 2018 at 19:55

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