SDB:Making Temporary Changes to a GRUB 2 Menu
Situation
You need to make a temporary change to the kernel parameters for a single boot process. For example, the display manager is not starting for some reason, and you want to boot to runlevel 3 (Multi-User Mode with Networking)
Procedure
Start the system and at the GRUB 2 boot screen, move to the menu entry to edit using the arrow keys, and press the 'E' key.
Use the arrow keys to navigate to the 'linux' line (or 'linuxefi' line for UEFI systems) then press the 'End' key (or Ctrl+E). Pressing 'Home' (or Ctrl+A) will move the cursor to the beginning of a given line.
Edit the kernel parameters as required. For example, if wanting to boot to runlevel 3, add a space and your runlevel number at the end of line.
Once the required changes are made press Ctrl+X to boot.