Arch Linux on a WM8650 netbook

UPDATE 20th November 2012: Due to recent changes in the Arch Linux boot process, this tutorial is no longer valid. You can still download an old pre-built image and install it, as I explained here. But with this old image, updating the distro (with pacman -Syu) will most likely throw some errors and maybe even break the system. Also installing applications without updating the distro (with pacman -S application_name) will likely fail because of the not updated dependencies.

If you have searched the net for a very cheap tablet, maybe you have seen a lot of  7" chinese ones featuring the WM8650 SoC. This SoC has an ARM9 CPU running at 800 MHz, a DSP, a 2D graphics accelerator and a lot of peripherals.

I don't like tablets at all, but I found some cheap chinese netbooks containing pretty much the same hardware, removing the touchscreen and replacing it with a keyboard + touchpad. I couldn't resist and bought one of these netbooks in Aliexpress. It costed me around 50€, shipping costs included. The specs of this machine are:

• Wondermedia WM8650 SoC at 800 MHz.
• 256 MiB DDR RAM (I think it runs @ 800 MHz, but I'm not sure).
• 2 GB internal NAND Flash.
• 7" 800x480 pixels TFT screen.
• 3 USB Host ports.
• 1 Ethernet port.
• WiFi.
• Headphones and microphone ports.
• Internal 7,4V 1800mAh LiPo battery.
• 9V 1,5A power adapter.
• Android 2.2.

The Android distro that comes pre-installed is pretty usable even without a touchscreen. As the specs of this machine are really far from being impressive, it doesn't run butter smooth, but works very well.

Android is OK, but as an Arch Linux fan I am, I wanted to make this netbook run it, so I started searching the net to see if anybody had already made it. The only thing I found was a Debian port for these netbooks, using the kernel from a preinstalled Android distro. This Debian port works, but isn't very well optimized, and for example, boot time takes almost 2 long minutes.

The closest thing I found is an Arch Linux port for a WM8650 based tablet. This tutorial is really great and very well detailed, and my work getting the kernel built is almost entirely based on it. John has made a really good job getting the Linux kernel built for these tablets.

In this post, I will detail the process I have followed to get a base Arch Linux system running in this netbook, but I will skip the kernel build process (maybe I'll detail it in a later blog post).

OK, let's get our hands dirty. You will need a SD card. The minimum required size of the SD card is 2 GB, but I recommend using at least a 4GB card, unless you don't need a desktop environment. The steps to get Arch Linux running are:

1. Partition and format the card. To do it, I have used gparted application. First create a very small FAT32 partition, and name it BOOT. The smallest partition gparted allowed me to create was 33 MiB, more than enough (we need less than 4 MiB). Then create a ext3 partition using the remaining space, and label it ARCH_SYS.

Partitions created in the SD card

2. Copy the boot script (wmt_scriptcmd) and kernel (uzImage.bin) to the BOOT partition. Download them here. Then run:

tar -xjf alarm-wm8650-boot.tar.bz2 -C /run/media/doragasu/BOOT/

Make sure to replace "/run/media/doragasu/BOOT/" with the directory where the BOOT partition of the SD card is mounted.

3. Download the root filesystem and untar it in the ARCH_SYS partition:

wget http://archlinuxarm.org/os/ArchLinuxARM-armv5te-latest.tar.gz
tar -xzf ArchLinuxARM-armv5te-latest.tar.gz -C /run/media/doragasu/ARCH_SYS/

Make sure you replace "/run/media/doragasu/ARCH_SYS/" with the directory where the Arch Linux system partition is mounted, here and from now on. Also make sure to run it as root (write sudo before the tar command if you are not root).

4. Copy the kernel modules to the ARCH_SYS partition. Download them here, and run (as root):

tar -xjf alarm-wm8650-modules.tar.bz2 -C /run/media/doragasu/ARCH_SYS/

5. We are ready for the first boot. Unmount the SD card, insert it in the netbook and power it on. You should see the Android robot, and then the messages Loading Kernel... and Starting Linux... should appear. In a few seconds, you should be able to see the boot messages, and finally get the login prompt. The first boot will take a lot of time because udev has some problems and eats almost all the CPU. We will fix these proplems in the next step. Default password for the root user is root.
6. Udev needs the accept4() OS call, that is not supplied by the Android kernel I have built. To fix this, you have to install libaccept4. Download this package and put it inside the SD card (for example in /root). Then start Linux, login as root and in the console change to the directory containing the downloaded package and type:

pacman -U libaccept4-570-1-arm.pkg.tar.xz
echo /usr/local/lib/libaccept4.so >> /etc/ld.so.preload

Accept the installation of the library, and reboot. Udev should be working fine from now on, and boot time will be a lot shorter.

7. To extend battery life, power to the internal WiFi dongle is off by default. To enable it, you need to toggle the GPIO pin controlling its power. Download this package, copy it to the SD and install it with the following command:

pacman -U wmt-gpio-1.0-1-arm.pkg.tar.xz

Upon installing this package, to enable the WiFi chip, you have to input the command:

gpio 1:6:d8110040:d8110080:d81100c0

And to disable the WiFi chip:

gpio 0:6:d8110040:d8110080:d81100c0

You can create two scripts with these commands, or if you always use WiFi, you can add the first one to /etc/rc.local, to enable WiFi each time the system boots.

8. To read the battery charge level, use the following command:

cat /sys/class/power_supply/wmt-battery/capacity

9. To change the screen brightness, you have to write a number between 0 and 255 (the greater, the brighter) to /sys/class/leds/lcd-backlight/brightness. For example:

echo 200 > /sys/class/power_supply/wmt-battery/capacity

You can also add this line to rc.local to set the screen brightness to your favorite level each time the system boots.

Now you have a fully functional base Arch Linux install. It's highly recommended to update your system (pacman -Syu). Then you can start installing your favorite utilities, window manager, etc., by following the instructions documented in the awesome Arch Linux Wiki.

I'll give you some hints for Arch Linux newbies. Skip them all if you are experienced with this distro. You can start by editing /etc/rc.conf. This file contains some basic configuration parameters, like for example the timezone (TIMEZONE), the hostname (HOSTNAME) and some basic network configuration parameters (that default to DHCP on the Ethernet port). Very important in this file is the last line, detailing the services started when the system boots, and the order in which they are started. I usually remove netfs from the list, replace network with networkmanager (you'll have to install it first) and add dbus (you'll need it for the window manager and some more programs). If you use networkmanager instead of network daemon, make sure you put it after dbus.

To set the locale (in case you don't want the default en_US.UTF8), you have to follow these steps:

1. Edit /etc/locale.gen. This file details the locales generated by the system. You can replace/add the desired locales to this file. For example, to generate locales for spanish language, add:

es_ES.UTF-8 UTF-8  
es_ES ISO-8859-1  
es_ES@euro ISO-8859-15  

2. Generate the new locales by running (with root privileges):

locale-gen

3. Edit /etc/rc.conf and change the default locale to the desired one. Of course, the locale must be one of the included in /etc/rocale.gen. For example, for spanish:

LOCALE=es_ES.UTF-8

To change the root password, use the command passwd. To create a new user, use the command adduser. Leave the default parameters, but when asked for additional groups, enter the following:

audio,lp,storage,video,wheel,games,power,scanner

It's highly recommended to install sudo and add the user to the sudoers. Just follow these steps:

1. Install sudo:

pacman -S sudo

2. Allow all the users in the wheel group to use sudo. Run the visudo command, and uncomment  (remove the '#') the following line:

# %wheel ALL=(ALL) ALL

If you don't know how to use the vi editor, press the [I] key to [I]nsert text, when you finish, press [ESC] to enter command mode and write :wq to write the file and quit the editor. If you mess something up, just press [ESC] to switch to command mode, and write :!q to quit without saving changes. Then try again the visudo command.

And that's all for today. If you followed this tutorial to the end, congratulations! You should be able to launch GNU/Linux in your shiny WM8650 laptop, with the locale, timezone and (hopefully) Ethernet network properly configured. You should be also able to login as a non privileged user, and use sudo to run tasks as root. If you have questions, feel free to ask them.

What? You don't like the console? Don't worry. In the next chapter, we will learn how to install a graphical desktop environment. Stay tuned!

TROUBLESHOOTING:

I have patched the kernel to make it compatible with the environment of the Android distro that comes pre-installed in some netbooks. You should be able to boot Android (without the SD card inserted) and GNU/Linux (with the SD card inserted). It works on my netbook, but it looks like there are different hardware revisions of these netbooks, and some of them, may require to change some variables in the environment stored inside the internal Flash memory. Typical problems that may arise are for example not being able to use the Ethernet port, or losing the ability to read the internal battery level. If you experience these problems, I can provide you with a modified wmt_scriptcmd that changes some variables of the environment stored in Flash, to make the broken things work. But I'll not post it here unless someone asks for it, because if you overwrite some variables, you may break things in the Android kernel (i.e. you can loose the battery level information in Android). And if you didn't back up that variables first, you might not be able to fix these problems.

Other problem that may arise, is that WiFi may not work. WiFi in these netbooks is implemented using an internal USB WiFi dongle. The one used in my unit has a Realtek RT8188CU chipset. I had to search the net for a compatible driver (rtl8192cu) and merge it into the kernel drivers. If your netbook uses a dongle with a different chipset, WiFi may not work. Enable WiFi with the gpio command, run lsusb and show me its output. I'll try to help you to get the dongle working.

Of course you may find a lot more problems. Feel free to ask for help! You can also read the follow-up to this post: Arch Linux on a WM8650 netbook (II).