I had an abrupt shutdown and I was wondering if their was any shell command to force checking for errors and updates.
If you arent in dev-mode then the check for errors should be done every boot - named from Google "verified boot".
To force checking for updates you could use in the Chrome-Browser:
Wrench-Icon (upper right) -> About Chrome
then you will get a window with the actual version displayed (here stable-channel 16.0.912.77) and a button "Search for updates" (here in Germany named "Nach Updates suchen")
At the Link Additional information you could switch to the dev- or beta-channel, but for going back to stable it could be that your chromebook has to be restored via the recovery-usb-stick or a long wait until the stable-channel reaches the version-nummer from the de- or beta-channel.