nodm screen may not show up depending on plymouth and tty
Binary package hint: nodm
nodm may not start up properly. When this bug occurs, nodm starts up and runs the script that it is setup to run, but nothing shows up on the screen. The X display should be shown instead.
This is because the tty that nodm allocates for X may end up being either tty7 or tty8, where tty7 works correctly and tty8 does not always work. tty8 should work as well, but it does not at least in every case, which may depend on the used graphics card. I have noticed this bug happening especially on nvidia graphics hardware, both with nouveau and the closed driver, but have been unable to replicate this with some other graphics chips (I do not actually know if they always use tty7 or not, but no visible problems have appeared).
What happens is that plymouthd reserves tty7 in the boot process, and if nodm is started while tty7 is reserved, nodm ends up taking tty8, and the X display is not shown. It is also not possible to switch to tty8 to see the X display. If plymouthd exists before nodm is started up, nodm takes tty7 and everything is normal.
It is possible to avoid this by requesting plymouth to quit before starting up nodm. Adding a line:
plymouth --wait --quit || true
before "start-stop-daemon ... --exec /usr/sbin/nodm" in /etc/init.d/nodm is one way to work around this problem.
$ lsb_release -rd
Description: Ubuntu 10.04.1 LTS
$ apt-cache policy nodm
*** 0.6-1 0