Update to MacOS Big Sur can render Macs unusable
No time right now?
Three months after the release of the MacOS Big Sur desktop operating system, installing the update can under certain circumstances still lead to fatal errors and render the Mac unusable.
MacOS 11 Big Sur was officially released to all users in November 2020 after a long beta period. Since then, Apple has released two updates with fixes and general improvements. However, it did not seem to fix all serious problems, as reported by the Mr. Macintosh blog. If there is not enough storage space available during the update process, data can be lost.
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MacOS 11 Big Sur requires at least 35 gigabytes of free space
According to Mr. Macintosh (via 9to5 Mac) Do not check the installation program for MacOS Big Sur before starting the update whether there is enough memory available for the update process. As soon as the system starts the update process, the Mac can no longer respond and data can be permanently damaged. Even if the update process seemed to be running smoothly, towards the end of the installation the message: “An error occurred preparing the software update.”
According to Apple, the first update from MacOS Sierra or later to MacOS Big Sur requires at least 35.5 gigabytes of available space – but that does not include the 13 gigabyte installer for MacOS Big Sur. When upgrading from an earlier version, Big Sur even needs up to 44.5 gigabytes of free space, explains Apple.
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MacOS Big Sur – versions 11.2 and 11.3 also affected
Apple doesn’t seem to have discovered the bug yet, since according to Mr. Macinstosh it can still be reproduced with Big Sur versions 11.2 and the 11.3 beta. Those who have already installed Big Sur on their computer shouldn’t have any problems with OTA updates to a newer version, they say.
If the error occurs, the system can only be saved using a backup using a time machine. The entire hard drive must be deleted and MacOS reinstalled. The problem is more problematic with Macs with a T2 chip, whose data is protected by Apple’s hard disk encryption, Filevault 2, according to the blog post: In recovery mode, the correctly entered password is no longer accepted and you do not have access to your own data.
If there is no current backup, the only option is a second Mac on which MacOS 10.13 or 10.14 is installed – only with these versions can the stuck Mac be accessed and the hard drive decrypted via the target disk mode. Again, this is not feasible with new MacOS versions.
