1. Edit your software repository list to include gOS. Open a terminal window (Applications>Accessories>Terminal), and type
sudo gedit /etc/apt/sources.list.
2. Enter the following:
deb http://packages.thinkgos.com/gos/ painful main
3. Save the file.
a. You must also add the key so that aptitude will not warn you that the source is untrusted. At the terminal enter
b. Add the key by entering the following on the terminal
sudo apt-key add gos_repo_key.asc
c. Update aptitude through this command
sudo aptitude update
4. To install gOS via terminal, I suggest using aptitude instead of apt-get. It makes the removal easier (in case you want to revert to plain Ubuntu). Note that you need an Internet connection for this one. Enter the command
sudo aptitude install greenos-desktop
5. After installation, log out. In the login screen, press F10. Click on Select Sessions, then click on Enlightenment. Click Ok.
6. After entering your user name and password, you will be prompted whether to make Enlightenment as the default desktop. If you are just checking, click Just this time.
And you will now see the default green theme.
To remove gOS, issue this command at the terminal:
sudo aptitude remove enlightenment
Aptitude will automatically remove greenos-desktop package.
Enlightenment DR17 is the environment used by gOS. If you want the latest version installed, add this line to the repository list (follow step one above):
deb http://e17.dunnewind.net/ubuntu gutsy e17
On the terminal, use aptitude to install the latest Enlightenment:
sudo aptitude install enlightenment
Note that DR17 is still under heavy development, and may be buggy. The upside is that you get the latest modules and gadgets (like the mixer and network gadgets).
If you want to try the beta of the new version, named Rocket, add this to the repo list instead of the one stated at step 1:
deb http://packages.thinkgos.com/gos/ reloaded main
Be warned, though. According to a post in Ubuntu Forums, installing Rocket will remove several packages, including network-manager.
(Steps taken from the unofficial gOS Forum.)