So, the Chromebook comes with ChromeOS preinstalled.
It's a cool system but I prefer something that has a terminal and ssh as first class application at the very least. The terminal in ChromeOS is ridiculous.
The internal eMMC is not very large but it's quite fast and you can use a SDXC card or USB thumb drive for further storage.
To install a sane system you will first need to
switch to developer mode.
Hold down the ESC and Refresh keys and poke the Power button. To enter Dev-mode you first invoke Recovery, and at the Recovery screen press Ctrl-D (there’s no prompt – you have to know to do it). It will ask you to confirm, then reboot into dev-mode.
You’ll still have to run “crossystem dev_boot_usb=1” and reboot once to boot from USB drives with Ctrl-U.
To run that command you boot the device in dev mode. press something like
Ctrl-Alt-T to enter a shell, then type
shell to really enter a shell. The
SD card slot counts as
USB, ew.
I prefer to first install a new system on removable media so that it's easy to dissect when it turns out broken and still leaves you with a working system in the device. The Chromebook allows booting from a SD card so you can keep ChromeOS on disk while playing with GNU/Linux.
To install you will obviously need a SD card, a SD card reader to use with your PC (you can possibly install the image directly on the Chromebook but it's easier to do on a sane system with command history, etc.
On your PC you will need ARM
crosscompiler - eg. from
emdebian you can get
arm-linux-gnueabihf-gcc (Debian 4.7.2-5) 4.7.2.
To actually use the compiler symlink
arm-linux-gnueabihf-gcc-4.7 as
arm-linux-gnueabihf-gcc somewhere in your path.
You will also need
debootstrap, qemu-user-static, u-boot-tools, device-tree-compiler, vboot-utils, vboot-kernel-utils, gdisk and
cgpt.
device-tree-compiler in Debian stable is version 1.1 which is too old.
device-tree-compiler 1.3 from testing should work.
A Chromebook
kernel source can be found here:
https://git.chromium.org/chromiumos/third_party/kernel.git (the chromeos-3.4 branch). Using GNU/Linux with this kernel is unsupported. If you experience bugs that don't happen with chromium you are on your own. There are
some nice guides for building the kernel.
To compile run something like this:
chromeos/scripts/prepareconfig chromeos-exynos5
Edit the .config - you will want to disable LSM because it prevents you from loading modules:
CONFIG_SECURITY_CHROMIUMOS=n
The Debian compiler does not support -fstack-protector-strong so you will want to
patch out the -strong part.
You can
patch the kernel config to allow building middle mouse emulation on non-mac:
CONFIG_MACINTOSH_DRIVERS=y
CONFIG_MAC_EMUMOUSEBTN=y
The config is pretty minimal so make sure you have drivers for any external hardware you plan to connect to your Chromebook.
make ARCH=arm dtbs
make ARCH=arm CROSS_COMPILE="arm-linux-gnueabihf-" -j6
mkimage -f kernel.its kernel.itb
echo "console=tty1 debug root=/dev/mmcblk1p3 rw rootwait" > config.txt
vbutil_kernel --pack kernel-image \
--keyblock /usr/share/vboot/devkeys/kernel.keyblock \
--version 1 \
--signprivate \
/usr/share/vboot/devkeys/kernel_data_key.vbprivk \
--config config.txt --vmlinuz kernel.itb --arch arm
You will need WiFi
firmware (IIRC the
sd8797_uapsta.bin).
You can easily build an
arm chroot and install/set up packages you will need on your fresh Linux system.You will need at least one kernel partition 4MB in size (the ChromeOS kernel is about 3.6MB) and a root partition for your Linux installation. You can include more than one kernel partition so that you have a backup and can recover easily when you install a broken kernel.
The ChromeOS loader uses
GPT and is particular about flags and partition types so you will need a GPT partitioner that can set them.
gdisk can set partition types properly - chrome
kernel is
type 7f00. The bootloader will not load a kernel from partition with different type. To match the mmcblk1p3 above in the kernel parameters make two kernel partitions followed by an ext4 partition which will be mounted as root. Linux filesystem is supposed to be type 8300 which is the default in
gdisk.
To copy the kernel image use
dd if=kernel-image of=/dev/<your card device>1 bs=4M (size of your kernel partition). Copy the arm chroot to your card using tar or whatever. Don't forget to add the kernel modules and firmware.
To mark the kernel partition as bootable you need to set flags with cgpt or other tool that can manipulate them. Example:
cgpt add -i 1 -S 1 -T 5 -P 10 -l KERN-A /dev/<your card device>
cgpt add -i 1 -S 1 -P 10 /dev/<your card device>
-i gives the partition number, -S is 'succesful' and partitions with this flag zero are not bootable. -P gives priority. With multiple bootable partitions the one with higher P is selected. -l is label which can be used to name the partition but is not used by bootloader. T is number of tries but needs not be set - T 0 partitions are also bootable. Note cgpt is a
partitioner and operates on
whole disk. The partition it opertaes on is selected with -i. Some guides give wrong instructions showing cgpt used on a partition.
