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Question: Cannot boot into new drive's Recovery Mode, to erase old drive

Hi!


2012 Mac Mini with 1TB HDD, Sierra macOS installed, with Server.

Upgraded and installed a 1TB SSD, in addition to the HDD.


Can boot just fine from the SSD, restarting etc. each time, starts up on the SSD.

Set the Start Up disk inside System Preferences, and by holding down CMD and selecting it, after trying the startup manager.


Both SSD and HDD now have macOS Sierra with Server installed.

I now want to wipe the original HDD.


At first, was met with the cannot erase because cannot unmount issue.

So realised I needed to boot into Recovery Mode, on the SSD, and wipe the HDD from there.


Problem >> I cannot boot into Recovery Mode on the SSD. Each time, regardless of which drive I am in when I reboot, as soon as I hold down CMD+R to start recover, it chimes, and then fires up the HDD drive (I know given how slow the progress bar loads).

So since I'm in Recovery mode on the HDD, I cannot (understandably) erase it...


What do I do now? How am I going to wipe the HDD, if I cannot get into Recovery Mode on the SSD?

Suggestions?

Mac mini (Late 2012), macOS Sierra (10.12)

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Mar 16, 2018 2:59 PM in response to Kappy In response to Kappy

Many thanks for the reply!


I first plugged the SSD in as an external - then booted into recovery mode, and used that to install macOS Sierra onto the SSD.

Then used the migration assistant to transfer all my files from the HDD onto the SSD.

Installed the SSD into the Mini after I quickly checked all was working, and went from there.

Mar 16, 2018 2:59 PM

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Mar 16, 2018 3:06 PM in response to Neal_Cassady In response to Neal_Cassady

Regardless of which Recovery HD you are using you can still format the HDD and install macOS on it.


Install El Capitan or Later from Scratch


  1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
  2. Select Disk Utility from the Utility Menu and click on Continue button.
  3. When Disk Utility loads select the volume on the HDD (indented entry, usually Macintosh HD) from the Device list.
  4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
  5. Set the Format type to Mac OS Extended (Journaled.)
  6. Click on the Apply button, then wait for the Done button to activate and click on it.
  7. Quit Disk Utility and return to the Utility Menu.
  8. Select Install OS X and click on the Continue button.


This will install the version of OS X you had installed.

Now, if you want to boot from the Recovery HD on the SSD, then you will need to set the SSD as the boot disk using Startup Disk preferences, then booting from it.

Mar 16, 2018 3:06 PM

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Mar 16, 2018 3:57 PM in response to Neal_Cassady In response to Neal_Cassady

So since I'm in Recovery mode on the HDD, I cannot (understandably) erase it...


Out of curiosity: why not? That is how one can erase a hard drive when there are no other drives involved - you boot into recovery and wipe the drive (to reinstall, for instance).

Mar 16, 2018 3:57 PM

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Mar 16, 2018 10:45 PM in response to Kappy In response to Kappy

I have done everything in the above (selected Start up disk to SSD etc.), but it will not erase - since it cannot unmount.


That appears to be the key issue - it says the disk is in use, cannot unmount, so cannot erase.


That happens when I boot into SSD, and try erase through Disk Utility, or boot into Recovery - and try from there.

Mar 16, 2018 10:45 PM

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Mar 17, 2018 10:05 AM in response to Eric Root In response to Eric Root

I can.


But I'm trying to avoid wiping the drive. I have a TM backup of the original HDD. When installing the SSD, I used the Migration Assistant to transfer everything off the HDD onto the SSD. So the TM backup is still on Sierra - nervous that if I wipe, might have an issue restoring from the TM if the SSD is then upgraded to HS.


Force unmounting the drive in Terminal works - but obviously when the Installer tries, it cannot.

Mar 17, 2018 10:05 AM

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Mar 18, 2018 5:05 AM in response to Neal_Cassady In response to Neal_Cassady

Are you sure that the SSD has a recovery partition? You can erase the HDD using Disk Utility while booted from the SSD, no need to access recovery at all. But before you do you'd better make sure your ssd has recovery.

Mar 18, 2018 5:05 AM

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Mar 18, 2018 7:57 AM in response to Eric Root In response to Eric Root

Thanks Eric - at this point, I appear to be running out of options in any event.


Here's what I have managed to do over the weekend, after a number of issues arose:


After the advice above, I realised that I that the actual problem was not where I was trying to erase the drive from, but rather, that the drive was refusing to unmount.

Regardless of which drive's Recovery Mode was being used (and this included a bootable USB HS installer, AND the Internet Recovery Mode – the HDD would not erase since it could not be unmounted.


Finally, after surfing around, I was pointed towards using Terminal, where I managed to "force" unmount the HDD, and after re-mounting it, I managed to erase the HDD.

In other words, after booting into the SSD, I simply ran Terminal - forced the unmount, and could then erase as per normal.

It is now working as expected - and is seen as an empty drive on the system, that I can copy data onto.


I want to point out at this point that First Aid in Terminal confirmed that both SSD and HDD are functioning properly – with the exception of whatever was clinging on to it, keeping it from unmounting.


I then tried to upgrade the SSD drive, to High Sierra - and lo and behold, the same issue arose. It then dawned on me that this was the same issue that was preventing my upgrading to HS, when I only had the HDD – something I had tried periodically over the past few months.

The installer, when it was trying to work its magic, could not unmount the drive mid-installation, and so stopped the upgrade process.


There are other threads on the Apple Support Forum, where this is explained in detail - unfortunately, the solutions that worked for other's over there, were not working for me.


Since I can 'force' unmount the SSD, but the installer cannot, I am stuck - and cannot upgrade. Obviously, with me using the Migration Assistant to transfer the data off the HDD over to the SSD when I installed the latter, has seen the underlying 'mount' problem transferred across as well.


So it would appear that if I have any hopes of getting my Mini onto HS, as my MBP is, I will need to wipe it and start over.


I am very cautious about that though, since the Mini is the repository of my canonical 248GB Photos library...

So want to try and keep it intact if at all possible, or at least, be able to restore from the TM backup.


If I do wipe, and upgrade the SSD/Mini to High Sierra, I should be fine to restore from a Sierra backup, correct?

Mar 18, 2018 7:57 AM

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Mar 18, 2018 9:02 AM in response to Neal_Cassady In response to Neal_Cassady

If you upgrade the SSD to HS, you should be able to restore from a Sierra backup without any problems. I would do that using Setup Assistant, which should run on the first reboot after the installation.

Mar 18, 2018 9:02 AM

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Mar 18, 2018 9:12 AM in response to Neal_Cassady In response to Neal_Cassady

Just as a not necessarily helpful comment: I tried to update my MBA (running Sierra) to HS; it appeared to install fine and I used it for a few minutes before shutting it down for the night. The next day it would not boot. It would not recognize my external clone(s) - any of them. It would not boot into (any) recovery. The only thing I would get was a window saying the Mac OS cannot be installed on this computer. In other words, it would not do anything. It took me three days to get it back to work (many glitches and totally unexpected behavior), but I finally got it - seriously do not know how or why it suddenly worked.


I have therefore made the decision that this MBA will remain on Sierra (unless I can see another 3 day period in my life where I have absolutely nothing else to do).

Mar 18, 2018 9:12 AM

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Mar 18, 2018 11:46 AM in response to Neal_Cassady In response to Neal_Cassady

The problem here is that installing HighSierra is also converting the SSD to the APFS file system. It is not clear here if that is perhaps (partially) converted.

Go to the RecoveryPartition which is very very probably the "old" Sierra RecPart, as Mike Sombrio suggests. Then do the Install OS, and choose the SSD. See what you get:

When you restart in HighSierra you are all set.

When it is Sierra that starts up: unmount the HDD and upgrade again to High Sierra: decide if you want APFS conversion at the same time or not. If you decide that you want to wait with the apfs conversion, you can do that by not starting the Install HighSierra Installer. Instead open Terminal and start the install with the following command:

/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO

(this is one line)

(It is clear that the Installer file must be in the Applications folder).

Run High Sierra and when you are "ready", mount the HDD again, after setting the SSD as startup disk.

Mar 18, 2018 11:46 AM

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Question: Cannot boot into new drive's Recovery Mode, to erase old drive