nodm screen may not show up depending on plymouth and tty

Bug #714492 reported by Juha Erkkilä on 2011-02-07
26
This bug affects 5 people
Affects Status Importance Assigned to Milestone
nodm (Ubuntu)
Undecided
Unassigned

Bug Description

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
Release: 10.04

$ apt-cache policy nodm
nodm:
  Asennettu: 0.6-1
  Ehdokas: 0.6-1
  Versiotaulukko:
 *** 0.6-1 0
        500 http://fi.archive.ubuntu.com/ubuntu/ lucid/universe Packages
        100 /var/lib/dpkg/status

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in nodm (Ubuntu):
status: New → Confirmed
Michal Suchanek (hramrach) wrote :

it seems this still happens on Oneiric.

or perhaps nodm requires xinit but does not depend on it

Michal Suchanek (hramrach) wrote :

hmm, the workaround works for me.

Joona Manner (joona-manner) wrote :

One important observation related to NODM not starting every time reliably :

If you have installed normal package with Gnome, you must disable lightdm loading on background while starting NODM.

- to do this you just have to create file:

 /etc/init/lightdm.override

- and type in it:

manual

- and reboot the computer after that.

If gnome graphic interface is loaded on background when user wants to use e.g. NODM and Openbox instead of Gnome, loading lightdm ( Gnome graphic login interface) makes starting NODM totally random. Every once in a while system does not load NODM at all but ends up with normal Gnome Unity greeter, which is something that no one wants if thet want to use NODM.

James Cameron (quozl) wrote :

For me on 13.04 an alternate workaround was to configure /etc/default/nodm to start on vt8, although this leaves plymouth active on vt7, whether or not the splash option is on the kernel command line.

The workaround to add "plymouth --wait --quit || true" to /etc/init.d/nodm worked fine for me.

Initially the symptoms matched #1070677, which somewhat confused my investigation.

Ville Ranki (ville-ranki) wrote :

"me too".

Looks like nodm is not actively maintained anymore: http://bugs.debian.org/cgi-bin/pkgreport.cgi?dist=unstable;package=nodm

Any good alternatives available?

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