Ever since the first Chromebooks were released, it has been possible to run Ubuntu or other Linux distributions using Crouton (Chromium OS Universal Chroot Environment) on Chrome OS devices, but that requires to enable developer mode, which disables some of security features that come with Chrome OS.
Google has now make it easier and safer with Crostini VM that does not require developer mode. The only downsides for now are that it only works on Google Pixelbook, and you need to install/run Chrome OS v67 dev channel with the #enable-cros-container flag enabled.
Using Crostini is fairly straightforward. First start crosh terminal with Ctrl++Atl+t, and running the following command to create a VM, and launch a container:
vmc start dev
run_container.sh --container_name=stretch --user=<username> --shell
This will start a Debian Stretch environment with networking and GUI support, so you can install & run programs like you would in Debian (e.g. apt install htop).
Kevin Tofel at AboutChromebooks managed to install the Eclipse IDE (See screenshot above) and Sublime Text using the VM in order to write code with his Chromebook, while John Bowdre showed he installed Visual Studio Code, Gimp, Firefox, and apparently Chromium browser because… he could.
Crostini VM does not cover all use cases for now, as for example USB is not currently supported, and the VM is apparently taking a lot of memory, so Chromebook with 4GB RAM may not be usable with Crostini at this stage. Nevertheless it’s still an experimental feature, and things should improve over time.
Chromebooks may soon become much more interesting laptops, as beside running an operating systems to basically browse the web, they can now run Android apps, and upcoming support for Linux programs could be a game changer.