initrd

First up, you can modify the initrd environment to give yourself more programs if needed. Don't forget the shared libraries a program might need to run!

Boot the system and catch the Grub menu. If you can't catch it (because someone possibly set the wait to zero), hold down the left shift button during boot.

Press "e" to edit the kernel command line and add "break=" onto it, where is one of following:

It is sometimes useful to change an initrd to make additional programs available during initramfs shell.

To get to initramfs shell, add break=point to the kernel boot options, where point is one of top, modules, premount, mount, mountroot, bottom, init.

Extracting the contents of the initfs into a working directory: