There are many users of so-called Chrubuntu which have Ubuntu 12.04 running on their Samsung ARM Chromebooks. And I do not support them with any updates so they wonder how to upgrade to 13.04 release. So I decided to spend some time and help with it.
For this I installed Chrubuntu 12.04 on SD card (not on internal as I have own installation of Ubuntu there) and I will go though upgrade to 13.04 and document all steps here.
First thing: if your Chrubuntu installation fails on fetching 4.7MB of "ubuntu-1204-binak.bz2″ file then you probably started script with "sh" instead of "bash". Abort process and run it with "bash" — it really needs it.
But ok, you got your Chromebook booted to Ubuntu desktop (running Unity 2D). Remember: your password is "user". Open terminal (Ctrl+LAlt+t), get root and edit APT sources so they will point to "raring" instead of "precise". Now refresh APT data and run distro upgrade (I used "apt-get dist-upgrade").