High Sierra install fails - "unable to unmount volume for repair"

Have a 2012 Mac Mini.

Running Sierra.

Third party SSD running Sierra for more than a year.

Sierra was installed over the previous version of OS.

When trying to install High Sierra, system takes me to a screen that says "unable to unmount volume for repair". Asks me to restart and back to normal login.

Checked the primary HDD via Disk Utility. Everything appears to be ok.

Searched the discussion forum and internet. No solution found.

Any ideas?

Thank you.

Posted on Sep 26, 2017 10:58 AM

Top-ranking reply

etinin

Level 1

9 points

Posted on Oct 19, 2017 11:27 AM

Building upon previous answers, I have concluded that the problem is because the installer is glitched and can't convert the drive to APFS. This problem can easily be circumvented:

1 . Boot to internet recovery or a USB drive with the High Sierra Installer (standard Sierra recovery mode won't do).

2 . Go to Disk Utility and mount your Mac volume.

3 . Close Disk Utility and go to the command line terminal.

4 . Do diskutil umount force /Volumes/Macintosh HD/

Take note of your disk id. disk1 in my case.

5. Run diskutil apfs convert /dev/disk1s1

(replace disk1 with your disk id if needed)

6. Once this is done, reboot and High Sierra can be installed from either a USB drive or Internet Recovery mode (option+command+R)

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126 replies

cmaus

Level 1

20 points

Feb 5, 2018 11:47 AM in response to jaikishan30

You don’t do that from Recovery Mode.

Do it while your macOS is normally started.

Feb 7, 2018 9:23 AM in response to MBarrowclift

All good upto step 5, executing the command at step 6 gives error : “no such file or directory”

Feb 8, 2018 1:01 AM in response to dianeoforegon

Thanks for the update.. i really do not want to lose my data so any help on cloning would be really helpful..

Oct 30, 2017 4:49 AM in response to ttaallff

ttaallff,

I say, "Welcome to the Party!" 🙂 I tried this already, as I mentioned in a previous post. I also could get High Sierra to run this way, but had problems using Migration Assistant to restore from my Time Machine backup. Additionally, I'm running Server software and may end up with some permissions issues if the account IDs change.

Joe

Oct 10, 2017 9:40 AM in response to kluetin

Nope - not related to Mac Mini.

I can't upgrade my MackBook Pro (Mid 2014).

Nov 14, 2017 12:47 PM in response to dianeoforegon

Tried this from High Sierra install USB disk. Did not need sudo for disktuil to work. For my Mac mini 'diskutil unmountDisk force /dev/disk0 did the trick.

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High Sierra install fails - "unable to unmount volume for repair"