Although Chromebooks are pretty indestructible, it’s always wise to have a recovery disk, just in case.
Fortunately this is an easy task on a Chromebook:
in your webbrowser and you will presented with a very simple wizard to follow.
insert a usb drive (with 4GB or more) and the system will proceed to download the recovery image and burn it to your usb stick. Viola you are now prepared for the worst and can recover your Chromebook in the event of a failure.
Hope you never need it.