Upgrading from MacOS 11 Big Sur to MacOS 12 Monterey fails

[David Gr]

Trying, unsuccessfully to upgrade from MacOS 11 Big Sur to MacOS 12 Monterey - please can you help?

iMac17,1 (Retina 5K, 27-inch, Late 2015)

• macOS 11.7.10
• 8 GB DDR3
• 36GB free space available on 1TB SSD

Have tried:

1) System Preferences > Software Update - this simply hangs with a "Checking for updates..." message

2) App Store - goes to System Preferences > Software Update and hangs with a "Checking for updates..." message (as 1 above)

3) Direct InstallAssistant.pkg - downloaded from this link - InstallAssistant - MacOS Monterey 12.7.2 - this runs for about 45 minutes, then hangs with "About 1 minute remaining" message. During the time its running the amount of available data on the SSD reduces by about 4GB.

Any suggestions gratefully received. I would much prefer not to be stuck on Big Sur, as I'd like to continue to get security upgrades, at least for a little while longer.

Thanks

 

[Fishrrman]

This is a guess and it may be wrong.
But...

I have read that installing the newer OS versions requires A LOT of "extra space" on the internal drive.

Although it sounds illogical, 36gb may "not be enough".
You may need more like 60gb of "room" for the installer to "do its thing".

What I would try (and yes, this is "a job"):
First, back up your entire drive "as it is now".
Then, boot to INTERNET recovery (command-OPTION-R at boot).
Then, open disk utility. MAKE SURE you go to the "view" menu and choose "show all devices" (so that you can see the internal SSD).
Then, ERASE the ENTIRE internal SSD to APFS, GUID partition format.

NOW try the software installer again.
After the install, restore your data using setup assistant.

IMPORTANT:
To create the backup drive, I WOULD NOT rely on time machine.
Instead, I'd use either SuperDuper or CarbonCopyCloner to create a BOOTABLE clone of the Big Sur setup.
Then, if you run into problems, you still have a way to boot the iMac to the finder.

You can't do that with time machine!

Final thought:
I NEVER worry about "security upgrades".
The "main Mac" I'm using (and on which I'm typing this reply) is still running Mojave, and will forever more...

 

[David Gr]

hrrmanThis is a guess and it may be wrong.
But...

I have read that installing the newer OS versions requires A LOT of "extra space" on the internal drive.

Although it sounds illogical, 36gb may "not be enough".
You may need more like 60gb of "room" for the installer to "do its thing".

What I would try (and yes, this is "a job"):
First, back up your entire drive "as it is now".
Then, boot to INTERNET recovery (command-OPTION-R at boot).
Then, open disk utility. MAKE SURE you go to the "view" menu and choose "show all devices" (so that you can see the internal SSD).
Then, ERASE the ENTIRE internal SSD to APFS, GUID partition format.

NOW try the software installer again.
After the install, restore your data using setup assistant.

IMPORTANT:
To create the backup drive, I WOULD NOT rely on time machine.
Instead, I'd use either SuperDuper or CarbonCopyCloner to create a BOOTABLE clone of the Big Sur setup.
Then, if you run into problems, you still have a way to boot the iMac to the finder.

You can't do that with time machine!

Thank you Fishrrman - sound advice.

 

[David Gr]

Issue fixed.

Turned out to be my anti-virus - Intego VirusBarrier - interferring with the update. Feel embarrassed that I didn't think of that before asking for help. Apologies for wasting anyones time.