Turn on developer mode
I’m using a Samsung ARM Chromebook so to enter developer mode I would need to first invoke the recovery mode by holding down Esc and Refresh keys and poke the Power button.
At the recovery screen press Ctrl-D (there’s no prompt). It will ask you to confirm, then reboot into developer mode. It’ll take about 15 minutes or so to reinstall the computer for developer mode.
In developer mode the Chromebook will show the scary boot recovery screen every time it boots up from powered-off state. You can either press Ctrl+D or wait 30 seconds to continue booting. Don’t hit the space bar unless you want to go back to original mode.
See the resource link below how to enter developer mode for other machines.
Log into your Chromebook and download latest Crouton at https://goo.gl/fd3zc.
Open a new terminal tab by hit Ctrl+Alt+T, and type shell and hit enter.
If you just want command line interface and no Ubuntu graphic desktop, run sh ~/Downloads/crouton -t cli-extra
This will save a lot of disk space and installation time. If you are more comfortable with regular Ubuntu desktop then use sh ~/Downloads/crouton -t unity. To see other available targets, run sh ~/Downloads/crouton -t help. The crouton script will take a while to finish. Just wait and hit enter when prompted.
You can now run Ubuntu on your Chromebook. You can open an Ubuntu terminals by hit Ctrl+Alt+T and