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Maybe boot.debug1mounts should be documented as well? It's the same thing but it fails after neededForBoot file systems are mounted.

@jakobrs so what would you propose for the text

      Like <literal>boot.debug1devices</literal>, but continues stage1 until <literal>neededForBoot</literal> file systems are mounted.
      This may help with e.g. [making the keyboard work].

Does debug1mounts go further than debug1devices?

That's pretty much it, yes. It's basically just a variant of boot.debug1devices that fails only after all neededForBoot file systems are mounted, which may or may not be beneficial depending on what you're trying to do.

There are some technical details (see here), but those don't really matter. boot.debug1mounts fails right before stage 2 is launched, so it can be useful if you want to modify stuff inside the initrd with the system being "as usable as possible". And as a bonus, the file system is mounted for you.

It's also worth pointing out that if you exit from the shell launched by boot.debug1mounts, boot.debug1devices, boot.debug1, debug1 or boot.shell_on_fail, the boot will proceed normally, from where that option was handled. So you can, for example, use boot.debug1mounts to move system files before starting the rest of the system. And then you can just exit and the boot process will proceed as usual, provided you haven't broken anything. This does not apply if you choose the "start an interactive shell having pid 1" option, because the new shell is execed

@jakobrs you seem to know it in a lot more detail than me :) Would you mind updating the documentation for these options? If not, I'll try to copy what you wrote.

Is this fine?

merged, sorry for missing it