This is how to edit grub so you can restart ubuntu in text mode without loading the video drivers and Unity desktop
sudo gedit /etc/default/grub
Comment out the line that says GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
Add the following line:
GRUB_CMDLINE_LINUX_DEFAULT="text"
When you are finished with the edit it sould look like this:
# GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX_DEFAULT="text"
save grub - then run sudo update-grub
Reboot Ubuntu:
sudo shutdown -r now
This is how to edit grub again so it will restart in graphics mode
This time you want to uncomment GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
and comment out GRUB_CMDLINE_LINUX_DEFAULT="text"
It should look like this:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
# GRUB_CMDLINE_LINUX_DEFAULT="text"
save the file
Update grub:
sudo update-grub
Reboot ubuntu