How do you shut down Chrome OS?

How does crouton work to run Chrome OS and Ubuntu simultaneously?

• Crouton allows users of Chrome OS to basically alt+tab to Ubuntu and back to Chrome OS, leaving all processes of each OS running in the background when using the other. A video of it in action is at http://gigaom.com/2013/03/05/video-chromebook-pixel-running-chrome-os-and-linux-simultaneously/, where goes from Chrome OS to playing with Audacity and Skyping his son in Ubuntu, and back to Chrome OS while continuing the video call. How does this work? Crouton code: https://github.com/dnschneid/crouton

• Answer:

  Crouton allows you to run Linux in a chroot environment within Chrome OS. Simply put, Ubuntu is running and sharing the same resources as Chrome OS, with a virtualized file system. Further explanation of chroot from crouton's Github page: Like virtualization, chroots provide the guest OS with their own, segregated file system to run in, allowing applications to run in a different binary environment from the host OS. Unlike virtualization, you are not booting a second OS; instead, the guest OS is running using the Chromium OS system. The benefit to this is that there is zero speed penalty since everything is run natively, and you aren't wasting RAM to boot two OSes at the same time. The downside is that you must be running the correct chroot for your hardware, the software must be compatible with Chromium OS's kernel, and machine resources are inextricably tied between the host Chromium OS and the guest OS. What this means is that while the chroot cannot directly access files outside of its view, it can access all of your hardware devices, including the entire contents of memory. A root exploit in your guest OS will essentially have unfettered access to the rest of Chromium OS.