How can I force a Ubuntu kernel to fail mounting / and drop into the initramfs rescue shell?

Question

I am trying to customize the initramfs rescue environment and would like to force the kernel to fail mounting / and drop into the (initramfs) rescue shell, as opposed to single user mode.

How can I do that?

NB: I know how to hook into initramfs-tools to achieve the customization steps, but I need to be able to verify the result.

Solution

This will drop you into an initramfs shell:

• Start your computer. Wait until the Grub menu appears.
• Hit e to edit the boot commands.
• Append break=mount to your kernel line.
• Hit F10 to boot.
• Within a moment, you will find yourself in a initramfs shell.

If you want to make this behavior persistent, add GRUB_CMDLINE_LINUX_DEFAULT="break=mount" to /etc/default/grub and run grub-mkconfig -o /boot/grub/grub.cfg.

Comments

[0xC0000022L]

thanks! This is spot on what I was looking for. Two things: 1.) I had to press Ctrl+C before being dropped into the initramfs shell and 2.) because I use GRUB2 the line is called linux :)