crouton

Crouton is a set of shell scripts that let you run a full Linux environment alongside Chromium OS (the operating system on Chromebook devices) without replacing it. The technique it uses is called a chroot: instead of booting a second operating system, it runs Linux inside a sandboxed portion of the same running system. This means no speed penalty from virtualization, but also no hard isolation between the Linux environment and the rest of the device, since they share the same kernel and hardware.

The project is now end-of-life. The author announced in the README that ongoing changes to Chromium OS (stricter security settings, removal of certain browser extension APIs, and Google's transition away from Chromium OS toward Android) have made further development pointless. The repository is locked and will eventually be archived. For older Chromebook devices that are no longer receiving updates, crouton still works and can give those machines a second life running Ubuntu, Debian, or Kali Linux. For devices running Chromium OS version 111 or newer, various features have stopped working in successive releases.

To use it, a Chromebook must be put into developer mode (a hardware-level setting that disables some security checks). After that, you download the crouton installer script, open a terminal on the Chromebook, and run it. The installer sets up a Linux distribution in a chroot directory and provides commands to enter and exit the Linux environment. An optional Chrome browser extension offered better integration between the two environments, but that extension no longer functions on current devices due to the Manifest v2 removal.

For people on current Chromebooks who want a Linux environment, Google's own Crostini project (Linux on Chromebooks, built into the operating system settings) is the maintained alternative. The README explicitly points readers there.

The README is written with a jokey, conversational tone. The project itself is a serious technical tool, but the author's personality comes through clearly throughout the documentation.