GoKawiilProgress Report: Linux 7.1 Previous
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Linux 7.1 is now here, and of course with it comes another progress report. We’ve got M3 progress, Apple bugs, and more!
Welcome back Master Boot Record
When you long-press the power button on your Mac to bring up the boot picker (or use the Startup Disk application), what you see listed as Asahi is not actually the partition with the operating system on it. Apple’s boot tooling will only work with what it considers to be a “valid” macOS installation inside an APFS container. So that we can use Apple’s bootloader and avoid needing users to run commands from Recovery every time they want to use Asahi, the Asahi Installer creates a small APFS container (2.5 GB) with just enough of macOS on it to convince Apple’s tools that it is a bootable installation of macOS with m1n1 as its kernel. This arrangement worked completely unchanged from macOS 12 to macOS 26, and Apple even fixed a couple of bugs in their tools that are only encountered when attempting to boot raw binaries that are not a real XNU kernel.
Shortly after the release of the macOS 27 Golden Gate developer beta however, we began receiving reports that people were no longer able to boot into Linux on their machines — the option had simply disappeared from both Startup Disk and the boot picker! Obviously this is quite concerning, and so we made investigating this a priority.
Inspecting the disk using diskutil revealed that all Asahi-related partitions were still present on the disk after upgrading to macOS 27. No data loss was occurring, which is a positive sign. Additionally, Asahi was still bootable on the same machine when using the boot tooling from a second install of macOS 26.
chaos_princess began inspecting Apple’s own macOS Installer and old streams from way back when we were first poking at Apple’s boot tools. The macOS Installer sets some APFS metadata before rebooting the machine, which further investigation revealed to be a flag that marks the volume as bootable. Until macOS 27, the boot tooling simply ignored this flag entirely. After setting the flag manually on an Asahi APFS container, it becomes available in the macOS 27 boot picker with no further changes.
Going forward, all new Asahi installs will have this flag set automatically by the Asahi Installer. We’ve also added an installer mode that will fix existing installations. If you’ve installed the macOS 27 developer beta and cannot access your Asahi install, please run the installer again and use the “Fix macOS 27 boot picker compatibility” option.
chaos_princess has also developed a program that can be run from Linux to fix the issue. While we would eventually like to deploy this fix automatically, we need more testing data to confirm that it is reliable and will not destroy anyones’ filesystems. That’s where you come in. If you are willing to help us test this, clone this repo, then build and run it from Linux before upgrading to macOS 27. If your Asahi volume is still selectable as a boot target from macOS, it has worked. Do be sure to let us know how it went by popping in to one of our channels on OFTC or Matrix, especially if you run in to any issues.
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