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

When booted in recovery mode, I am able to force unmount the disk.

I don't wish to REFORMAT and lose everything. Even though I do have multiple backups (TimeMachine and Carbon Copy Cloner [aka CCC]), I don't want to have to go through everything (including licensed apps) to make sure everything is correctly restored and all the licensed app are working correctly after the install (assuming that actually works).

I've tried the unmount followed by running the APFS conversion command - that's where it also fails (see earlier posts).

> using disk utility, got disk error, tried again, then it worked

I get that frequently. I think you can safely ignore it. If you want you can likely find the full guide for the software (or even the source code "the real guide" and see what the error code is), however you'll likely find what you already know: it gives and error code the first time but not the second 🙂 Perhaps avoidable by doing steps in some order: but easy is as easy does.

@dianeoforegon

I've heard that suggestion about also having a clone and plan on incorporating that into my backup strategy. However, I'm confused as how this will help me upgrade to macOS High Sierra. Won't restoring from a clone simply bring me back to my macOS Sierra installation? Also, does simply dragging the files from the Backups.backupdb folder restore all of the OS specific settings? I'm trying to upgrade from macOS Sierra Server to macOS High Sierra Server. There are some critical databases the need to be installed and I'm not sure just dragging them over will work. I'm upgrading my server based on an Apple Knowledge Article I read on the subject.

Joe

Wow - I spent an entire day messing around and even swapped out the HDD for an SSD in my Mac Mini Late 2012 - those two commands should be run before running the installer from your live OS X installation.

Having just done that and rebooted, now getting the "Installing: 41 Minutes Remaining" screen....

I thought this could not possibly work, but had some time to give it a try - renamed those files and 30-45 minutes later my MacMini was running High Sierra.

Why 2 months after 10.13s release has Apple not addressed this in the installer.

Thanks for sharing this Andy, ends 2 months of frustration.

This worked for me as well. However, at one point the second mv command did not find the original file. I tried to install anyway. Big mistake. It stalled and I had to reinstall from time machine. This time both mv commands were successful and the install went through without a hitch.

Thank you very much!

Awesome after so many reboots and failed attempts at getting the system volume to unmount etc, it beggars belief that Apple haven't published this specifically or indeed included it as part of the update...its almost as bad as Microsoft!

I've been an IT systems engineer for over 25 years and it took me until 2011 to turn to Apple as my personal preference and something as simple as this, is likely to put off those less IT literate. Get on it Apple before your reputation suffers.

Thanks Andy

Thank you for the post, I have been searching everywhere to find help with this. Really stupid question, so sorry, but I am not super computer literate... would you mind explaining where/how I input that code to fix the unmount volume issue?

Thank you very much, andy260!

This solved it for me, too.

(iMac 5K 2015 with 3TB Fusion Drive)

I just called back Apple Care to tell them about this solution, since the second level support wasn't able to solve this back in September 2017.

Wish I could report that the solution offered here, worked for me!

2012 Mac Mini 1TB HDD running macOS Sierra. Never had any issues before, until now.

Booting from USB-installer, sees the same issue.

Hoping someone has further suggestions...

Andy had the solution for me.

I have a Mac mini Server 2011 with an OWC Mercury EXTREME Pro 6G SSD

The High Sierra install balked until I ran those two commands in terminal. I'm not sure what they do or why, but the installer worked immediately after. Thank you Andy.

I have seen discussion from the OWC crowd of changing firmware on the drive, so I am stating that I did not do anything but run those two commands for the install to work. Good luck everybody.

Can you possibly tell me how to do this as if you are talking to a 3rd grader? I have purchased my first mac computer and I tried to erase it (to return it to Best Buy) and then reinstall macOS and I am receiving this error after it tries to install for about 45 minutes. I ran it twice. When I click on repair macintosh HD I get the unable to unmount error as well. I dont understand the commands you mention. How do I get to a point where I can put in commands?

My mac os doesn’t start normally.. :-( i guess something crashed my os and then i get apple logo and progress bar.. even after 100% completion its still wait there.. so i have only option of recovery mode..

I tried reinstall OS x option in recovery mode and received following error:

“MacOS could not be installed, cannot unmount the volume for repair”

I do not want to erase my hard drive/ loose any data.. plz help.. Thanks in Advance..

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

Ok, let me give you the issue background.. one fine morning when i started my macbook it showed me grey screen with apple logo and progress bar, it completed 100% but nothing happend.. then i tried resetting pram no luck.. then safe mode but could not open... tried reistall os x via recovery mode option still same status.. tried internetrecovery as well but no luck.. then moved the kext files as mentioned in the one of the forums: https://www.justinsilver.com/technology/os-x-el-capitan-10-11-1-hanging-on-boot- fixed/

After this also no luck, again tried reinstall os x via recovery option.. and then after completion i get “cannot install macOS Unable to unmount volume for repair”..