Having your Apple MacOS stuck in a dreaded boot loop can be an exasperating experience. (For those of you lucky enough not to know what a boot loop is, it occurs when an operating system cannot successfully boot to the desktop screen. Instead, on system power-up, the OS goes through the familiar boot-up process but halts at a certain point. If you’re lucky, you’ll get an error message which might give a hint of what the problem might be). In MacOS, boot loops can occur out-of-the-blue due to OS corruption or they can typically occur after the user has attempted to install a fresh version or updated version of their operating system.
Recently, we had a client who experienced this very problem. They tried to upgrade their operating system from Catalina to Big Sur. However, their 256GB SSD did not have enough space. The installation of the OS update files never completed, but now on start-up of their system they would receive a message that “An error occurred preparing the software update”. As a result, they were unable to access their desktop and they had no recent backup.
Luckily, we had heard about this problem before. The earlier versions of the MacOS Big Sur (11.6.1, 11.6.2) installer files have a bug in them. Namely, the installer setup file does not check the size of the disk before the installation process begins proper. Therefore, if you don’t have the pre-requisite of 35GB of free space needed to store the temporary install files, this re-boot loop problem manifests itself. This bug also interferes with FileVault 2 encryption hence making the APFS volume invisible to Target Disk Mode (TDM). TDM will see “Macintosh HD” but not “Macintosh HD – Data” which is the folder you want! And if you’re thinking some bootable Linux tool could image the disk – because of the problem with FileVault 2, that avenue is also closed off.
Thankfully, there is a solution to this problem, albeit convoluted, which goes beyond the scope of this blog. But the long and short of it is this; we got all the data back for our delighted client. The lessons of this case are simple. Always have a complete backup before you start upgrading your MacOS system (or any OS for that matter). And secondly, always try to avoid deploying the first iterations of an operating system because, even with MacOS, these versions can be more bug prone.
Drive Rescue offer a data recovery service for Apple in Dublin, Ireland for devices such as MacBook Air, MacBook Pro and iMacs. We’ve been recovering data from Apple devices since 2007 with excellent success rates.