Update 2009-11-11: This post is about old version 9.04, please consider the better-working 9.10 I am writing about here instead.
My brand new little Macbook Air arrived the other day and I spent quite some time getting Ubuntu 9.04 (Jaunty) to run on it. Since I could not find alot of info on the web I thought I would switch to English for today and scribble down some notes that might help others out there!
First of all, I don't know if it is possible to set up netboot for the installation, I could not be bothered and my colleague was kind enough to lend me a USB CD drive so I went for the 32-bit CD install.
The Bootcamp app in Macos can be used to resize and make space for the Ubuntu partition. Holding the alt key during the DOOOOOOH sound at boot time gives a boot menu where the USB CD drive is recognised. However, just booting the plain vanilla Ubuntu disc reboots the computer and the USB port dies.
It can be healed by doing an SMB reset (google it). I did not know what that was so I ended up calling support and the guy told me to unplug the USB drive and hold left shift + ctrl + alt + power button for 12 seconds. Sometimes that works but sometimes I also have to do and additional 5 sec powerbutton... whatever that does?
To get the installation (or just live session) going, add noapic and remove quiet and splash from the kernel command line (F6 to add noapic and then arrow keys and backspace to edit the commandline).
I started a live session and installed cryptsetup before I started the installation. This makes is possible to create an encrypted partition that can be used as root during installation. (_cryptsetup luksFormat /dev/sda3_ and cryptsetup luksOpen /dev/sda3 cryptoroot and mkfs.xfs /dev/mapper/cryptoroot, note that you need to save about 200 meg for a separate /boot partition if you opt for the encrypted root).
During the installation it is a good idea to click Advanced and make sure Grub is only installed to the beginning of the Ubuntu partition, or it will fail. To get a nice start menu for MBR check out rEFIt.
There are some Macbook specific packages to enable most of the hardware available from the Mactel Support Team.
The only problem I have now is that Ubuntu only boots about half of the times I try. The other half of times the laptop just reboots again. The trick I have found so far is to have noapic and acpi=force on the command line.
Will update this post when I know a better way of booting :-)
And a final word about the Macbook Air -- it is a really nice piece of hardware that I can really recommend. Using it together with Ubuntu gives me the best of both worlds: world class hardware and OS at the same time!