Arch Linux on a Macbook Air 4,2

Installation Overview (tl;dr)

This describes an Arch Linux install, not Ubuntu, and doesn't use the typical BIOS compatibility mode suggested in most linux-on-Macbook guides. As such, you shouldn't expect a point-and-click install.

This document is a work-in-progress, but will get you around the few small issues that are specific to this laptop.

1. Preparation
   1. Download the most recent archboot ISO
   2. Write the ISO to a USB stick using dd
   3. Prepare hard drive in OSX: (shrink your OSX partition in Disk Utility)
2. Partitioning and Installation
   1. Boot the USB stick (hold option key to select boot drive)
   2. Partition hard drive using cgdisk (GPT partitions, not MBR)
   3. Install Arch to the partitions you just setup
   4. Install grub2 as bootloader, manually copying to the EFI system partition
   5. Reboot into the new system; display will be incorrect resolution - don't fret!
3. Install a new kernel
   1. Download and configure linux-3.1.1 source, and apply i915 resolution patch
   2. Compile and install new kernel
4. Post-install: Xorg, etc.

Preparation

Before installing anything, you'll need to prepare a USB stick, and shrink your OSX partition using the native Disk Utility.app.

Note that there's no need to use Boot Camp to create a MBR partition table, since we're going to boot using pure EFI mode which uses the GPT partition table which is already present.

Download the most recent archboot ISO

As of this writing, the most recent archboot release is 2011.10-1. If you're reading this from the future, grab the most recent version and send me some cool tech from your timeframe.

As stated on the Arch Linux page, you should use one of the many download mirrors; the archboot iso should be found in, low-and-behold, the /iso/archboot directory of your closest mirror.

Write the ISO to a USB stick using dd

Insert your USB stick. You'll need to unmount it without 'ejecting', since that also disconnects the USB device.

# Find your USB stick; remember the device path, something like /dev/disk2
$ diskutil list
# ... and unmount it
$ diskutil unmountDisk /dev/disk2

# Note the use of the "raw" disk device, /dev/rdisk
$ dd if=/path/to/archlinux-2011.10-1-archboot.iso of=/dev/rdisk2 bs=8192

Prepare hard drive in OSX

Open Disk Utility.app (in /Applications/Utilities). Use it to shrink your existing OSX partition, leaving enough room for your planned Linux install. I chose to leave 64 GB of my 256 GB drive, but it's entirely up to you.

Partitioning and Installation

This section of the install doesn't deviate greatly from the usual Arch Linux install process. The primary differences are the need for manual partition creation, and manual installation of the GRUB2 bootloader to the EFI system partition.

Boot from the USB stick

This is the easy part: just hold down the option key before the apple logo appears on the gray firmware boot screen. Using arrow keys (or the mouse), choose the USB stick which will be mis-labeled "Windows".

GRUB will start up; choose the normal kernel.

Partition hard drive using cgdisk

Before doing anything in the Arch setup script, you'll need to create one or more partitions manually using cgdisk1. cgdisk manages a GPT parititon table, rather than the traditional MBR-style partitions.

I created one small 100MB partition for /boot, leaving the remainder of the free space for my root / partition. I didn't make a swap partition, but that's up to you. I've yet to use more than 1GB of ram in my usage so far!

Install Arch

Proceed through the normal Arch setup menus and dialogs as you would on any other machine. Once you reach the partitioning section, though, be careful! Don't let Arch do any partitioning of its own; instead, just move on and choose the partitions that you've already created and tell the script where to mount them.

Install GRUB2 to EFI System Partition

When you get to the bootloader question, make sure to choose grub2. The script will fail to fully install it, complaining about the EFI system partition.

Swap over to a shell, and install it manually:

# mount -t vfat /dev/sda1 /boot/efi
# cd /boot/efi/EFI
# mkdir boot
# cp grub/grub.efi boot/bootx64.efi

Note that the EFI/boot/bootx64.efi path is very important. The OSX EFI firmware is hardcoded to look for alternative EFI bootloaders there on 64-bit machines.

Reboot into the new system

Once you've finished up the Arch setup script and GRUB bootloader installation, you should reboot into the new system. Hold option again to get the list of boot options, and choose "EFI Boot". You should get the familiar GRUB menu; choose the fallback kernel option, since the current (as-of-this-writing) Arch-distributed kernel has issues with the keyboard when not in HID mode.

You'll get a bit of garbage on the right and bottom edges of your screen. The i915 driver fails to detect the native resolution of the internal LCD panel properly, but it's still usable.

Install a newer kernel

To fix the keyboard issues, you'll need at least version 3.1.1 of the Linux kernel. This version includes a number of fixes for the MacbookAir4,x series, including the keyboard driver.

To fix the display issues, you'll need to patch the i915 driver. The patch includes a hardcoded set of timings, overriding what the driver (improperly) detects.

Follow the process on the Arch Wiki page Kernel Compilation without ABS, with the following small changes:

Patch the i915 driver

You'll need to patch the i915 driver with the display timings appropriate for your machine. There are, at this time, five known panels in the Macbook Air 4,1 and 4,2 models. There is an Ubuntu-specific script that contains all of the modelines, but requires apt to install the get-edid utility which will identify your display.

If you don't already know which panel your machine has, you have two choices. Either install get-edid yourself, and follow along with the fix-i915.sh script by hand, or run the following in OSX:

ioreg -lw0 | grep IODisplayEDID | sed "/[^<]*</s///" | xxd -p -r | strings -6

Once you know which panel model you have, download the fix-i915.sh script from http://www.almostsure.com/mba42/fix-i915.sh, and apply the patch within with the appropriate modeline for your panel.

NOTE If enough people have trouble with this, I may wrap it up in an Arch- specific script.

Configure and compile

Follow the directions on the above-linked Arch Wiki page to configure and compile your custom kernel.

Add a bootloader entry for your kernel

There are two grub.cfg files, which can be confusing. One is in /boot; this is the wrong one, and unused during EFI boot. The other is on your EFI system partition, in EFI/grub/grub.cfg.

Add an entry to the EFI grub.cfg for your new kernel, but to be safe leave the Arch-native kernel in there too.

REBOOT!

Post-Install

The post-installation process is the same as for any other Arch system. You'll likely want to install Xorg (the intel graphics driver works flawlessly), and pm-utils + acpid for suspend support.