Samsung Chromebook

These instructions are written for installing to a USB drive with the sda device, assuming no other USB drives are plugged in. For an SD card, click here to magically adjust the instructions for the mmcblk1 device that an SD card will register as.

1. Get a root shell as described in the previous section.
2. Since ChromeOS will automatically mount any partitions it finds, unmount everything now:

   umount /dev/sda*

3. Start fdisk to create a GPT partition table:

   fdisk /dev/sda

4. At the fdisk prompt:
   1. Type g. This will create a new empty GPT partition table.
   2. Write the partition table and exit by typing w.
5. Partition the micro SD card:

   cgpt create /dev/sda
   cgpt add -i 1 -t kernel -b 8192 -s 32768 -l Kernel -S 1 -T 5 -P 10 /dev/sda

6. To create the rootfs partition, we first need to calculate how big to make the partition using information from cgpt show. Look for the number under the start column for Sec GPT table which is 15633375 in this example:

   localhost / # cgpt show /dev/sda
          start        size    part  contents
              0           1          PMBR
              1           1          Pri GPT header
           8192       32768      1   Label: "Kernel"
                                     Type: ChromeOS kernel
                                     UUID: E3DA8325-83E1-2C43-BA9D-8B29EFFA5BC4
                                     Attr: priority=10 tries=5 successful=1
   
       15633375          32          Sec GPT table
       15633407           1          Sec GPT header

7. Replace the xxxxx string in the following command with that number to create the root partition:

   cgpt add -i 2 -t data -b 40960 -s `expr xxxxx - 40960` -l Root /dev/sda

8. Tell the system to refresh what it knows about the disk partitions:

   partx -a /dev/sda

9. Format the root partition:

   mkfs.ext4 /dev/sda2

10. Download and extract rootfs tarball:

    cd /tmp
    curl -LO http://os.archlinuxarm.org/os/ArchLinuxARM-armv7-chromebook-latest.tar.gz
    mkdir root
    mount /dev/sda2 root
    tar -xf ArchLinuxARM-armv7-chromebook-latest.tar.gz -C root

11. Flash the kernel to the kernel partition:

    dd if=root/boot/vmlinux.kpart of=/dev/sda1

12. Unmount the root partition:

    umount root
    sync

13. Reboot the computer.
14. At the splash screen, instead of pressing Ctrl-D to go to ChromeOS, press Ctrl-U to boot to the external drive.
15. After logging in as root (password is "root"), you can connect to a wireless network by running:

    wifi-menu

16. Initialize the pacman keyring and populate the Arch Linux ARM package signing keys:

    pacman-key --init
    pacman-key --populate archlinuxarm

Better touchpad responsiveness

Create the file /etc/X11/xorg.conf.d/50-touchpad.conf and add the following to it:

Section "InputClass"
        Identifier              "touchpad"
        MatchIsTouchpad         "on"
        Option                  "FingerHigh"    "5"
        Option                  "FingerLow"     "5"
EndSection

Enable audio

1. Install alsa-utils: pacman -S alsa-utils
2. Run alsamixer as root.
3. Select correct sound card by pressing F6 and selecting '0 Snow-I2S-MAX98095'
4. Arrow right until you see four items starting with Left Speaker Mixer, and press M on all four channels to un-mute them.
5. Arrow right some more until you find four more starting with Right Speaker Mixer and un-mute them as well.
6. Arrow all the way back left to the Speaker channel and raise the volume a little. Keep it low (< 50ish), since alsa will let you get dangerously high for these speakers.

Alternatively, the following commands can be issued per channel to amixer. Requires alsa-utils as well.

amixer -c 0 set 'Right Speaker Mixer Right DAC1' unmute 
amixer -c 0 set 'Right Speaker Mixer Mono DAC3' unmute
amixer -c 0 set 'Right Speaker Mixer Mono DAC2' unmute
amixer -c 0 set 'Right Speaker Mixer Left DAC1' unmute
amixer -c 0 set 'Left Speaker Mixer Right DAC1' unmute
amixer -c 0 set 'Left Speaker Mixer Mono DAC3' unmute
amixer -c 0 set 'Left Speaker Mixer Mono DAC2' unmute
amixer -c 0 set 'Left Speaker Mixer Left DAC1' unmute

Suspend when closing the lid

Install acpid and pm-utils: pacman -S acpid pm-utils

Edit /etc/acpi/handler.sh and near the bottom you'll see the button/lid section. Add pm-suspend to the close section to look like:

button/lid)
    case "$3" in
        close)
            logger 'LID closed'
            pm-suspend
            ;;

Enable and start acpid:

systemctl enable acpid
systemctl start acpid

Closing the lid will now trigger a suspend, and opening it will wake the system.

User permissions for backlight control

To allow all users to modify the backlight control at /sys/class/backlight/backlight/brightness, create and edit the file /etc/tmpfiles.d/brightness.conf with these contents:

f /sys/class/backlight/backlight/brightness 0666 - - - 800

On boot, systemd will now set the permissions of that control file to be world writable. Acceptable values are 0-7.