With the current state of the initrd, the-tool is currently not exiting if systemd-mount exits with non-zero status, which is problematic in and of itself, but this combined with the fact that mounts are not effectively "re-tried" because systemd-mount starts a transient unit with the args that the-tool uses means that if the mount initially fails the first time, we will never try again.
On top of all that, there is a race between the mounting /dev/disk/by-label/ubuntu-seed and systemd-modules-load.service because in order to mount /dev/disk/by-label/ubuntu-seed, we need to have the nls_iso8859_1 kernel module loaded (which it is by systemd-modules-load.service).
This race combined with the first point about the-tool never trying again means that when we hit this race we will fail to mount /dev/disk/by-label/ubuntu-seed, and then never effectively re-try it, infinitely looping in the initrd, and thus never proceeding or failing the-tool, and finally we can't get a debug shell in the initrd because the debug shell depends on the-tool exiting (or probably more accurately depends on something else failing which depends on the-tool).
The right thing to do here I think is to have the-tool depend on systemd-modules-load.service.
MP up: https:/