Some macOS system administrators are facing issues upgrading to macOS Big Sur 11.1, which was released to the public last week. As detailed by ArsTechnica, the bug in question causes the macOS 11.1 update to disappear from System Preferences.
The problems seems to be that Macs are requesting the macOS Big Sur 11.0.1 update rather than 11.1:
Developer Victor Vrantchan, of the open source MicroMDM project, says he’s found the problem. Some Macs are erroneously requesting 11.0.1 instead of 11.1 from Apple’s update server—which update is then rejected if the machine in question is already running 11.0.1 or newer, as most such are.
Upon a restart, the macOS Big Sur 11.1 update will reappear in the System Preferences application but then disappears again. The report explains that the problem only seems to affect Macs associated with a Mobile Device Management system. Removing the MDM profile makes the update visible:
Removing the MDM profile—for you non-Mac folks and non-sysadmins, that’s Apple’s misleadingly named Mobile Device Management service, which allows education and enterprise orgs to manage and “supervise” fleets of macOS and iOS devices—also makes the update visible. That said, mortals should not try this workaround lightly; messing with MDM has potentially severe impacts on system security, and there’s no guarantee that re-enrolling the Mac in its workplace will go smoothly, either.
The issue is further compounded because Apple is no longer offering delta and combo macOS updates as standalone downloads, as we reported yesterday.
This issue should be able to be resolved through a server-side fix by Apple. A thread on the Jamf support forums has more details about the problem, plus some additional issues users are currently facing.
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