For those who prefer to watch the boot process by default (With out having to press the Esc key).
Open a Terminal and run gksu pluma /etc/default/grub
Find the line #GRUB_TERMINAL=console and uncomment it.
This is done by removing the # in front of GRUB_TERMINAL=console
Example:
# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=console
Save and close the file.
Then in the Terminal run sudo update-grub
The next time you reboot you will see the boot process instead of the graphical display.
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To switch it back to the graphical display, repeat the above instructions only this time comment out GRUB_TERMINAL=console.
Example:
# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
Not forgetting to run sudo update-grub once again or the changes will not be applied.