sobarch

T2 Macs

The ISO has a T2 boot entry, and the installer can replace one partition you made in macOS, leaving macOS and Apple's boot partition alone.

T2 Macs (2018-2020 MacBook Pro and Air, 2020 iMac, iMac Pro, 2018 Mac mini, 2019 Mac Pro) need a patched kernel to use their built-in keyboard, trackpad, SSD and audio. The prebuilt ISO ships that kernel (linux-t2, from the third-party arch-mact2 repository) next to the stock one. The stock Arch ISO plus command does not work on these Macs.

Tested on a 2018 MacBook Air only. Some support is flaky there: waking from suspend can leave features such as Wi-Fi, Bluetooth, the keyboard backlight or Touch ID broken until a reboot. Other models are untested. The t2linux state page tracks known issues.

1. Prepare macOS

  • In Disk Utility, add a partition (not a volume) to the internal disk and size it for Linux, at least 20GiB. Pick any format except APFS; ExFAT is fine. The installer replaces it, so its format doesn't matter, and it can't be resized later.
  • Keep macOS installed for now: the installer extracts the Wi-Fi and Bluetooth firmware from it.
  • In macOS Recovery, open Startup Security Utility, set Secure Boot to No Security and allow booting from external media.

2. Boot the ISO

Hold Option at startup and pick the orange EFI Boot entry. The GRUB menu preselects Sobarch installer for T2 Macs on Apple hardware. Don't switch to the first entry: it is the stock kernel, and the keyboard won't work with it. If you end up on it, the installer's console says so and tells you to reboot into the T2 entry.

The ISO extracts the Wi-Fi and Bluetooth firmware from macOS on its own before the installer starts. If that fails (macOS already removed, or an unsupported macOS version), use a wired or USB Ethernet connection.

3. Install into your partition

In the Disk step, each unmounted partition of at least 20GiB (other than boot partitions, APFS volumes and Windows reserved or recovery partitions) is listed as an extra choice, for example replace /dev/nvme0n1p3 "LINUX" (exfat, 60.0 GiB). Pick yours. The installer:

  • deletes only that partition and recreates its space as its own 1GiB boot partition and a btrfs root. macOS and Apple's own boot partition are never touched.
  • asks you to type the partition name (for example nvme0n1p3) to confirm.
  • turns rescue media off; the rescue ISO boots the stock kernel.

Choose the first entry for the whole disk only if you want macOS gone.

4. Make Linux the default boot

After the install the Mac still boots macOS by default, and you have to hold Option every time. Change the default once, either way:

  • From the startup picker: restart, hold Option until the picker appears, then hold Control and select the Linux entry (the orange EFI Boot, not the macOS volume).
  • From macOS: System Settings → General → Startup Disk, pick EFI Boot, and restart.

A macOS update resets the default to macOS; repeat the step afterward. The entry is only labeled "EFI Boot". To give it a name, run this in macOS (the install's boot partition is the 1GiB one next to your macOS volume; find its name in Disk Utility):

IDENTIFIER=$(diskutil info <PARTITION NAME> | grep "Device Identifier" | cut -d: -f2 | xargs)
sudo diskutil mount $IDENTIFIER
bless --folder /Volumes/<PARTITION NAME>/EFI/BOOT --label "Sobarch"

See the t2linux startup manager guide for details.

What gets configured

  • The linux-t2 kernel replaces linux, and the unsigned arch-mact2 repository stays enabled so the kernel keeps updating. Anything that repository ships is trusted without signature checks.
  • Fan control (t2fanrd), the Touch Bar (tiny-dfr), audio (apple-t2-audio-config) and the Wi-Fi/Bluetooth firmware fetcher (apple-bcm-firmware-fetcher).
  • t2-touchid, bound to the account you create, and fingerprint auth enabled on the lock screen.
  • Kernel parameters intel_iommu=on iommu=pt pcie_ports=compat, the T2 keyboard modules in the initramfs (so a LUKS passphrase can be typed), and a brcmfmac option that keeps Wi-Fi working with wpa_supplicant.

If the firmware wasn't copied during install, use a wired connection and run sudo apple-bcm-firmware-fetcher while macOS is still on the disk, or see the t2linux guide.

Touch ID

Touch ID works for the console login and the lock screen through the t2-touchid bridge, with these limits:

  • Only fingers enrolled in macOS work. Linux can't enroll or delete fingers.
  • Your password is still needed after a reboot, for disk encryption and to unlock the keyring; a fingerprint login doesn't unlock the keyring.
  • If no finger is recognized, the T2 wants the macOS account password once since it last lost power: boot macOS, log in with the password, then boot Linux again. Rebooting Linux doesn't reset this.
  • Check it with fprintd-list $USER and fprintd-verify.

Not handled yet

  • Hybrid graphics on the 15 and 16-inch MacBook Pros (the AMD GPU stays on and power use is higher than it needs to be).
  • Suspend problems some models have; see the t2linux state page.

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