Each boot will need this or it will revert to normal mode. After about 5m give or take, you will reboot, and you will be presented with the same screen as earlier, in which you will need to press CTL-D. The final screen will be a screen that gives you one last out, and will force a 30 sec wait before starting the wipe.

There will be a series of screens afterwards, read them and follow their instructions. When the first screen comes up, press CTL-D. Nice thing is if you do indeed make an error, you will not enable Devolper mode and will just reboot. The system will reboot and give you nasty warnings. Press and hold the ESC+Refresh+Power keys. Going to or from developer mode will force a PowerWash, so have anything that you want to keep backed up elsewhere (Google Drive, USB drive, LAN, somewhere else).

Firstly, you do need to be in developer mode.

Definitely worth checking out if you prefer the RPM over the DEB, as I definitively do. At the end of the page is the references, once accustomed to crouton, there is a Fedora based fork that, although behind the main project in stability, is coming along quite nicely.

Here are the details on getting crouton installed and running. Crouton is a wonderfully done tool for ChromeOS based machines (Chromebooks and Chromeboxes) that allows for the chroots of various linux (generally Ubuntu-Based) environments.

Crouton chromebook