And of course, you could also overwrite Google’s OS in favor of Linux.
Your mileage will vary depending on the gear, distro, and installation method.
On the bright side, Chrome OS only takes a few minutes to fully wipe and reinstall.

You don’t need to download this in advance.
To upgrade your install with new parameters later it’s possible for you to use the -u operator.
Also note that the downloads folder is shared between Linux and Chrome.
Helpful links:Ubuntu Packages-Crouton Commands-Linux Commands-GalliumOS Wiki
I don’t have a spare USB drive/SD card!
Although enabling/disabling developer mode performs a powerwash, this doesn’t appear to touch other partitions.