Monday, October 4, 2021

Stuck When Upgrading Directly From macOS Mojave to Big Sur

Mr. Macintosh:

The macOS Mojave to Big Sur upgrade is causing problems for some users.

The progress bar is getting stuck, leaving the system in an unbootable state. The user is locked out of their data.

This is especially relevant since Mojave didn’t get the latest round of security bug fixes. He recommends updating to Catalina first, and then to Big Sur.


This sounds like the issue @lapcatsoftware experienced in August. Crazy to imagine it is still a known issue since that is the suggested upgrade path for the now unsupported Mojave.

Mr. Macintosh:

The issue is confirmed on Big Sur versions all the way back to 11.4. (Maybe even earlier)

The account is still on the system, but no longer has admin privileges.


Update (2021-10-21): Mr. Macintosh:

If folders in multiple directories in the location below


have more than 20,000 files your upgrade could fail.

In some situations users have reported 500,000 – 2,000,000 files!!!

After updating to Catalina, I started having problems with hundreds of thousands of files collecting in those folders. There were so many in the same folder (at the level, not organized into a hierarchy like with Apple Mail’s message files) that it would take minutes just to view the folder in Finder, and SuperDuper backups would get stuck just reading the list of files to see if they were excluded.

Update (2021-12-16): Mr. Macintosh:

Apple has fixed this issue in both the Monterey 12.1 & Big Sur 11.6.2 full installers.

5 Comments RSS · Twitter

Yup, this was me, too. At first I thought it must just be connected peripherals, but no. It's a bug.

What about Monterey — is that likewise affected?

Yep me too -- three of them had problems, one locked me out of data as described: that machine has been sent to Apple, as the user did not have a backup.

Just to throw out some numbers:

In my department, 16 people upgraded their Macs from Mojave to Big Sur in August and September. For one of them, the Big Sur upgrade got permanently stuck as described above; the other 15 people did not experience this issue[1].

All Macs had FileVault turned on and were configured very similarly, so there was no clear indication why it happened with that one Mac but not the others. I had assumed that it was just a case of bad luck, not knowing that it seems to be a more widespread issue.

[1]: We had a surprising number of other issues after the upgrade, though: For instance, some people had duplicate contacts in iCloud, weird issues in (e.g., emails were displayed in the wrong folder), or Spotlight would no longer find most applications.

Benjamin Esham

When the Big Sur 11.6 update came out, it seemed to me that Apple *hadn’t* dropped support for Mojave: there were two CVEs mentioned in the release notes, and one of them (CVE-2021-30858) was fixed by the Safari 14.1.2 update (which Mojave did get) while the other (CVE-2021-30860) seemed not to have been an issue under Mojave to begin with, according to the NVD site.

But I took a look at the 11.6 security notes again today, and there are almost twenty more fixes listed now than there were when the update first came out. Many of these are shared with the 2021-005 Catalina security update. So it seems that Apple is still releasing critical security fixes for Mojave, but not “less critical” ones.

Hi Mr Macintosh,

This is to thank you for posting this great step by step tutorial and video on Youtube to fix this incredible issue from Apple.

I've experienced the "less than 1 minute remaining" bug after allowing my Mac to update to Monterey.

The root cause being there was not enough space in the first place to install the new OS on this Mac. The installation process ended up in an infinite loop, with only 16MB of free space left on the disk.

I've had to erase the whole disk as I did not manage to delete/free-up space using terminal commands in the "Volumes/Macintosh\ HD\ -\ Data" from the "Users" directory (directory never showed up, only directory "usr") while in Recovery mode.

In any case, here are a few "post-recovery" thoughts:
1) Thank you so much for the help, you have done here a much better job than what I could find on the Apple customer support forum,
2) It is completely un-acceptable that Apple place their customers in a situation where the whole hard drive contents may be lost, simply because the most basic computer science check that consists in ensuring enough free space is available is not performed by Apple in the first place !

Not to mention the time spent getting this Mac back up again and getting out of this infinite loop.

Mind you, isn't infinite loop the name of the street where Apple headquarters are located?

I really hope Apple would at least apologize for the trouble this MAC OS update has caused to all of us who have experienced this issue.

Sincerely, Magdalena.

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