Unable to erase Mac HD in Disk Utility. Should I just erase the entire SSD?

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Unable to erase Mac HD in Disk Utility. Should I just erase the entire SSD?

My start up drive is corrupted after updating Sierra. Goal is to reload OS Sierra on a reformatted SSD. Unfortunately I can't unmounts the Mac HD. Can I just erase the SSD (assuming this function works)?

I can't repair Mac HD in Disk Utility as I can't unmount it. Also can't erase it for the same reason.

I tried reinstalling OS Sierra from Recovery mode but got a Bad Command error message.

I tried creating a new partition to load OS Sierra but the partition failed.

I don't have a USB boot drive. Looks like I need the Sierra .dmg file to create one (I do have a PC I can use), but I don't have that file unless it is buried in on the Mac hard drive -- in which case I may be able to restore it from my cloud backup.

Hard drive is 7 months old. Looking into getting a thunderbolt cable so I can attach via USB to ensure it's not a data cable problem, but I don't have one yet. Data cable was replaced 4 months ago by Experimac tech.

MacBook Pro, macOS Sierra (10.12.1), null

Posted on Jul 30, 2017 4:07 PM

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Answer 1

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Kappy

Level 10

362,053 points

Jul 30, 2017 6:22 PM in response to vera k

I don't know exactly which model you have, but you can do a Network Restore provided your model is from Late-2011 or later. Below are the steps to reinstall a clean copy of OS X after erasing the disk. However, before you do this you could just try repairing the disk.

Clean Install of Sierra or El Capitan on a Clean Disk

Restart the computer. Immediately after the chime hold down the Command-Option-Rkeys until a globe appears.
The Utility Menu will appear in from 5-20 minutes. Be patient.
Select Disk Utility and click on the Continue button.
When Disk Utility loads select the drive (usually, the out-dented entry) from the side list.
Click on the Erase tab in Disk Utility's main window. A panel will drop down.
Set the partition scheme to GUID.
Set the Format type to Mac OS Extended (Journaled.)
Click on the Apply button, then click on the Done button when it activates.
Quit Disk Utility and return to the Utility Menu.
Select Reinstall OS X and click on the Continue button.

This should install the version of OS X that was pre-installed when the computer was new.

Repair the Drive for Sierra and El Capitan

Restart the computer and after the chime hold down the Command and R keys until the Utility Menu appears.
Select Disk Utility and press the Continue button.
Then select the indented (usually, Macintosh HD) volume entry from the side list.
Click on the First Aid tab in the toolbar and wait for the Done button to activate. Click on it, then quit Disk Utility.
Select Restart from the Apple menu.

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Answer 2

vera k Author

Level 1

13 points

Jul 30, 2017 4:57 PM in response to Kappy

The SSD is the only internal drive. But in Disk Utility it lists Mac HD as a subfolder. I don't have a boot disk of any kind. Frankly, I did not know this is something I should have which I know is quite silly. At least I believe my files are backed up with CrashPlan. Not sure if I will need to just reformat the drive or get a new one but in the future I will be sure to have a boot disk ready to go.

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Answer 3

Kappy

Level 10

362,053 points

Jul 30, 2017 4:57 PM in response to vera k

Does your computer have an internal HDD and an SSD? You aren't very clear on that. Do you have a computer from which you can boot into OS X? Do you have a copy of the OS X installer application, and what version does it install?

You cannot create a USB flash drive installer on a PC. Must be on a Mac.

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Answer 4

vera k Author

Level 1

13 points

Jul 30, 2017 6:26 PM in response to Kappy

I formatted the drive and reinstalled Sierra. The computer restarted on its own at the end of the Sierra installation and booted to a gray screen with a folder stamped with a question mark. I tried rebooting using Cmd-R and Cmd-Option-R but just got a blank gray screen. Now there is no chime. I'm at a loss as I can't even get to disk utility at this point, not that I was getting anywhere with it earlier!

Edited to add: I spoke too soon. Looks like I am slowly loading internet recovery mode. Will try again...

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Answer 5

vera k Author

Level 1

13 points

Jul 30, 2017 8:12 PM in response to Kappy

Well...looks like the problem may have been my 4-month old data cable. MacBook Pro Hard Drive Cable Failure - Free fix and preventative maintenance - Question mark - YouTube

I just covered it up with paper and suddenly was able to install Sierra and set up the Mac from scratch.

So looks like I erased my entire hard drive for nothing. Apple support told me it was the only way, but I should have known better. I forgot about the potential data cable problem. I might try covering it up with electrical tape as the video suggests as paper inside my hot mac seems like a fire waiting to happen.

Thanks for your help.

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Answer 6

vera k Author

Level 1

13 points

Jul 30, 2017 10:35 PM in response to vera k

Spoke too soon. Install seems to be incomplete and it again won't let me reinstall. Looks like I am in good company with others who struggled after installing or upgrading Sierra. Will try apple support again tomorrow. Thanks again.

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