An Ubuntu can be installed in a chroot, and accessed through a VNC client.

Why do this?

• You run Android and Ubuntu at the same time. Just press Home and you're back in Android.
• WiFi works out of the box - Ubuntu just picks up Android's connections.
• It's relatively stable. Also, this is a well-understood technique - people did it with many phones.
  

Why not do this?

• The graphics performance is abysmal. You view Ubuntu through a VNC client, and with 1024x600 it's really slow.
• Sound doesn't work out of the box (but you can listen to music through the Android player while working in Ubuntu)
• Many keys don't work: ctrl, alt, pgup, pgdn, tab (tab emits an X event however, just the wrong one). Esc works.
• Right and middle clicks don't work too. You have to go through VNC client menus to send a right click.
  
• Chromium doesn't work out of the box.
  

HOWTO

Prerequisites - root, busybox

1. On the desktop, mount the AC100 storage. Make sure you have exec and suid mount options. Then run 'debootstrap--arch=armel maverick <directory>' into a directory, say 'ubuntu'. Unmount.

2. On AC100:
$ su
# export PATH=/bin:/usr/bin:/sbin:/usr/sbin:$PATH
# export USER=root
# export HOME=/root
# export TERM=xterm
# busybox mount -o remount,exec,suid /storage
# cd /storage/ubuntu
# busybox mount -o bind /proc proc
# busybox mount -o bind /sys sys
# busybox mount -o bind /dev dev
# busybox mount -o bind /dev/pts dev/pts
# busybox chroot . bash
root@localhost:/#

That's the Ubuntu shell!

3. apt-get install lots of stuff. I feel ubuntu-desktop is too fat, but opinions vary. In the very least, we need tightvncserver and some window manager.

4. Set your timezone with dpkg-reconfigure tzdata.

5. Create a user with adduser username. You must also create a group with numeric ID 3003 and add yourself to it, otherwise vncserver's sockets will be blocked! So,
addgroup --gid 3003 sockets
usermod -G sockets -a username

6. Su to the user and create a file ~/.Xsession. Write there a list of stuff you want to run for a session, like a window manager. Here's an example:
xterm &
tint2 &
openbox

7. Run vncpasswd to set a vnc password, then run vncserver -geometry 1024x600. It will tell you the VNC display number, most likely :1.

8. Install android-vnc-client and connect to 127.0.0.1:5901 (actually, 5900 + the VNC display number).

Enjoy!