If you ever want to view Ubuntu's boot messages after Ubuntu has already booted, it's easy to do. I'm referring to the lines of information that appear on the screen as the system is booting. Sometimes there's some information that you might want to inspect but it scrolls too fast. 

All you have to do to view these boot messages is to run the following command in a terminal:

journalctl -b

And that will give you a nice printout of all of the boot messages that came up before the Ubuntu GUI loaded.

This command should work for other distributions besides Ubuntu.