Boot systems into different runlevels manually

This objective involves modifying the boot menu parameters before the system actually boots.

 There are several runlevels that one might realistically want to set the system to.

• runlevel 3: You might want to use runlevel 3 if your default runlevel is 5 to troubleshoot x-windows issues
• runlevel 1: Single user mode. 
• runlevel s: similar to runlevel 1
• runlevel init=/bin/sh or init=/bin/bash: Again, this is similar to runlevels 1 and s, but this allows you to change the password for root, at least in theory

Anyway, this is what you need to do in order to boot into any runlevel

1. Reboot your system
2. When you get to this screen, press any key

3. Select the kernel entry you want to boot and press e

4. Select the kernel line and press e

5. Append the runlevel, e.g. 1 at the end of the line and press enter
6. Press b to boot the system into your desired runlevel

You can check the current runlevel using who -r