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

Interesting I tried to do the force unmount and I got an error saying that the force failed...

I'm trying to zero out the drive. I imagine I'll have luck because I will be able to repartition/reformat the drive to APFS

So, I did this, as well (reformat drive in Disk Utility to APFS and install High Sierra from scratch). However, when I went to restore user data and applications from my Time Machine backup, it said it couldn't find a usable volume. Have you seen this message, too?

Joe

I have same problem

Re: macOS 10.13 could not be installed on your computer , unable to unmount volume for repair

Even the last Installer not solved this issue !

I hope Apple Solve this issue soon

I also have a 2012 (late) Mac Mini, with stock Apple SSD, running 10.12.6, and FileVault off. Same issue.

Disk Util reports no drive issues. Have tried a couple times from normal reboot and safe reboot. Reaches the same point (only a couple minutes into install) and reports message "Unable to unmount ... please quit installer and try again".

Also deleted and downloaded the installer on the chance from the time I originally tried Apple updated the installer. Last version of 'Install macOS High Sierra' I tried was 13.0.66.

Have 2 Mac Minis.

Update worked well on a

- MacMini, 8GB, 500GB HDD, middle 2011,

but not on a

- MacMiniSercer, 16 GB, 1TB SSD + 1 TB HDD, late 2012

Of course, hard disks are error free.

Hope that Apple will solve the problem soon. Seems to be a MacMini related problem ?

Same config here. Same error. Tried Apple Support - no luck. They suggested taking my iMac into an Apple Store (I'm lucky enough to have one within 20 miles). Not exactly the most portable of machines.

That didn't help.

First off... the step 2... says mount the Mac Volume....

Well - the HD is mounted already, so that doesn't seem to apply. If you mean the partition/volume under the HD should be mounted... well... there is no "child" shown under Macintosh HD.

With step 4, when I tried it I got

umount failed for force

Pretty much got stuck at that point

A bit of an update....

Between your steps 3&4 I did a "diskutil list" just to make sure I was dealing with the right drive.

Instead of your 4 step I did "distil amount force /dev/disk0s2" (disk0s2 being what's displayed in both the GUI diskutil and the diskutil list response)

That did successfully unmount the drive.

But the diskutil convert /dev/disk0s2 resulted in an error "exiting conversion operations with error code -69888"

That error code is an unmount error (inability to unmount), so it seems the convert option wants to mount and unmount before converting.

Also tried unmounting again and doing the "diskutil repair volume /dev/disk0s2" command. Which chugged along for a few minutes and reported back everything was fine.

So ya - still back at square one, once the volume is dismounted and them mounted again, it doesn't want to dismount unless "force" is used, claiming it's still in use. Which is really weird since... how? I booted from USB so how can it be in use?

Ok. Tried this. An earlier poster pointed out a possible discrepancy in step #2... so I ignored that as it was already mounted.

Here's the results I get from steps #3 & #4...

I should note that I have tried this with all external (Thunderbolt & USB) drives disconnected, apart from the booted external image.

My (much older) 17" MacBookPro (mid-2010) updated with no issues.

Oh, and if it helps, this is a bone-stock 27" 5k iMac as delivered (with internal SSD from Apple).

Well, in my case it's not a Mac Mini, but a 27" iMac.

No modifications. Boot drive is internal SSD as installed by Apple when I ordered the machine.

No funky software that you mention (virus checkers, disk copiers, ugh disk encryption yuk, etc). EtreCheck gives the machine a clean bill of health.

Etinin,

Does your procedure wipe the drive and do a 'clean' install? If so, I could do that before - I was running High Sierra from a clean install just fine. I got the unmount error when I tried to do an 'over-the-top' installation. I desire this route because I don't want to lose any data. I did try to use Migration Assistant to restore my files after the 'clean' install, but that never worked. I suspect it wouldn't let me restore from my Time Machine backup because the backup was made from a different OS --> Sierra. But, that's poppycock, right? Why would it care that I created the backup from a previous OS?!

I'm still at a loss...

Joe

Nope... no hacking here...all original equipment.

As for your software argument... anti-virus etc.... doesn't make a whole lotta sense many of us (myself included) are booting from USB.

But... there is some sort of software thing going on - yes... it's not a hardware issue as the Apple Store told me. But my impression, was that it was some Apple software thing, not third party.

Nope. Doesn't work. There's no installer in my Applications folder. Trash is empty. AppStore app only gives option to "Open", and does nothing on click.

Rebooted and AppStore allowed me to re-download.

Booted into recovery (Option+Command+R). Still no joy.

Opened terminal, force unmounted disk, then used Disk Utility to do "first aid" - reported no errors.

When attempting to convert to APFS (using Disk Utility), get the following:

com.apple.DiskManagement error -69888