Cannot remove unused disk partition

[Ken DL]

I have a Mac Book Pro (late 2011) with 750GB hard drive. A couple years ago I partitioned the disk so I could install a test version of a new Mac OS. (I think it was El Capitan at the time.) The test worked. I updated the main partition to the new OS. A couple years later, I am now running Sierra V 10.12.2.

I wanted to get rid of the test partition and merge the space back into my boot partition. So I erased all the data in test partition. However, I am unable to remove the test partition, which was about 180GB, and merge it back into one partition.

I just tried it again today using Disk Utility under 10.12.2. This time I got an error message: the partition task returned error code 8 and said it encountered some kind of corruption. Scary. Now the disk utility doesn't even show the test partition. It just the one running partition of about 560GB. So it appears that disk utility won't even let me manipulate the test partition anymore.

How can I erase that test partition now and recover the missing 180GB?

 

[Mike Boreham]

I have a Mac Book Pro (late 2011) with 750GB hard drive. A couple years ago I partitioned the disk so I could install a test version of a new Mac OS. (I think it was El Capitan at the time.) The test worked. I updated the main partition to the new OS. A couple years later, I am now running Sierra V 10.12.2.

I wanted to get rid of the test partition and merge the space back into my boot partition. So I erased all the data in test partition. However, I am unable to remove the test partition, which was about 180GB, and merge it back into one partition.

I just tried it again today using Disk Utility under 10.12.2. This time I got an error message: the partition task returned error code 8 and said it encountered some kind of corruption. Scary. Now the disk utility doesn't even show the test partition. It just the one running partition of about 560GB. So it appears that disk utility won't even let me manipulate the test partition anymore.

How can I erase that test partition now and recover the missing 180GB?

Only scary if you are not fully backed up! If you aren't I suggest you make a clone on an external before trying anything else.

Have you tried booting to the Recovery Partition and using Disk Utility on that to delete the partition?

Did you try running Disk Utility First Aid on the Volume you want to delete? Also run Disk Utility on the drive, rather than the volume, which checks the partition map.

Without seeing exactly what you are seeing, it is difficult to advise what next, but if the Drive level First Aid reports partition map problems you may need to erase the whole drive and restore from the clone.

 

[Ken DL]

Only scary if you are not fully backed up! If you aren't I suggest you make a clone on an external before trying anything else.

Have you tried booting to the Recovery Partition and using Disk Utility on that to delete the partition?

Did you try running Disk Utility First Aid on the Volume you want to delete? Also run Disk Utility on the drive, rather than the volume, which checks the partition map.

Without seeing exactly what you are seeing, it is difficult to advise what next, but if the Drive level First Aid reports partition map problems you may need to erase the whole drive and restore from the clone.

Thank you Mike. One question before I proceed: Does Apple's Time Machine provide a true clone from which I could restore, or do I need to use some other cloning tool?

 

[Fishrrman]

"Does Apple's Time Machine provide a true clone from which I could restore, or do I need to use some other cloning tool?"

What follows is my opinion only.
But if you take my advice, I guarantee a 98% chance of success.

First -- you DO NOT WANT TO USE Time Machine for this.
You MUST use either CarbonCopyCloner or SuperDuper (I recommend CCC because it will automatically take care of the recovery partition as well as your main OS partition).

BTW -- if you don't already have CCC, it is FREE to download and use for 30 days.
"Doing it my way" will cost you nothing out-of-pocket.

You will need an external drive (USB drive is fine).

Here's what to do:
1. Erase the external drive to Mac OS extended with journaling enabled.
2. Use CCC to clone the contents of your "working partition" (the one you wish to keep) to the external drive. CCC should ask if you want to clone the recovery partition as well. YES, you want to do this.
3. Once the clone is done, BOOT FROM IT by rebooting with the option key held down until the startup manager appears. Then select the cloned backup with the pointer and hit return.
4. Once booted from the clone, open Disk Utility.
5. Select the physical drive (internal) -- the "uppermost representation" in DU's drive list.
6. Next, ERASE the ENTIRE internal drive to Mac OS extended with journaling enabled.
7. I suggest you also run the repair disk function on the just-erased drive, to check it out.
8. Now, quit DU and open CCC.
9. Now, RE-clone the external drive BACK TO the internal drive. And again, clone over the recovery partition, too.
10. When CCC is done, go to the startup disk preference pane and RE-DESIGNATE the internal drive to be the boot drive.
11. Power down and DISCONNECT the external cloned backup
12. Now, press the power on button -- the moment of truth has arrived.

What results do you get...?

 

[Mike Boreham]

Thank you Mike. One question before I proceed: Does Apple's Time Machine provide a true clone from which I could restore, or do I need to use some other cloning tool?

Time Machine does provide a source for a complete restore of the entire drive, but as Fishrrman says I have found a Carbon Copy Cloner clone more reliable.

If the other suggestions I made (Disk Utility First Aid from the Recovery Partition) don't work or report a problem, you could do it as Fisherman says or do an erase and fresh install (from Internet Recovery) and use the clone as the source for Setup Assistant to migrate from at the end of the install process.