[regression] Unable to shut down, login screen keeps coming up

I catted the process list and contents of /dev when the system works fine and when the issue occurs. Maybe somebody can find the information useful in case the diffs show something valuable..

I don't think this is a duplicate. Even though the main symptoms are the same, this bug was introduced newly by some update in Lucid after the alpha release. Also the other bug report is about GDM, which has since been completely rewritten.

After investigateing this some more, I noticed that when the system is in the "broken state", the attributes of some devices are different. Listing of ls -la /dev/dvb/adapter0/ in normal state:
drwxr-xr-x 2 root root 140 2010-03-14 08:20 .
drwxr-xr-x 3 root root 60 2010-03-14 08:20 ..
crw-rw----+ 1 root video 212, 4 2010-03-14 08:20 ca0
crw-rw----+ 1 root video 212, 0 2010-03-14 08:20 demux0
crw-rw----+ 1 root video 212, 1 2010-03-14 08:20 dvr0
crw-rw----+ 1 root video 212, 3 2010-03-14 08:20 frontend0
crw-rw----+ 1 root video 212, 2 2010-03-14 08:20 net0

Listing in "broken state":
drwxr-xr-x 2 root root 140 2010-03-13 14:38 .
drwxr-xr-x 3 root root 60 2010-03-13 14:38 ..
crw-rw---- 1 root video 212, 4 2010-03-13 14:38 ca0
crw-rw---- 1 root video 212, 0 2010-03-13 14:38 demux0
crw-rw---- 1 root video 212, 1 2010-03-13 14:38 dvr0
crw-rw---- 1 root video 212, 3 2010-03-13 14:38 frontend0
crw-rw---- 1 root video 212, 2 2010-03-13 14:38 net0

The plus sign is missing. According to "info coreutils 'ls invocation'":

     A file with any other combination of alternate access methods is
     marked with a `+' character.

Maybe the bug is related to something in policykit or apparmor?

After asking about this on a mailing list, Martin Pitt kindly informed me that ACL is indeed used in Ubuntu and thus the +-signs. The ACL is set by udev using the ruleset in /lib/udev/rules.d/70-acl.rules

The rationale to use ACL in Ubuntu is that with it the system can control that e.g. inserted USB-drives can be accessed by the user who's console is currently active in stead of any user who is logged in.

I tried toggling consoles with Ctrl+Alt+F1-8, but it didn't help.

Restarting udev just says:
$ restart udev
restart: Rejected send message, 1 matched rules; type="method_call", sender=":1.51" (uid=1000 pid=2038 comm="restart) interface="com.ubuntu.Upstart0_6.Job" member="Restart" error name="(unset)" requested_reply=0 destination="com.ubuntu.Upstart" (uid=0 pid=1 comm="/sbin/init"))

udev logs, ConsoleKit logs etc. does not show anything suspicious.

However in syslog I found lines like:
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Could not determine active console
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 4 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 5 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 7 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 9 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 11 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 13 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 15 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 3 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 28 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 48 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 6 activation: Invalid argument
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error waiting for native console 54 activation: Invalid argument

Might they be related? Any tips on how to continue debugging this?

I'm seeing this in lucid with the latest packages installed as of 20/03.

Same behaviour as in description. Only possible to shutdown the machine using the command line, e.g sudo shutdown -h now, which then works as expected. Graphic shutdown from usermenu logs you out of your session but does not halt/reboot. Login in screen is displayed and shutdown/reboot options do not work.

This very much sounds like a duplicate of bug 544139. I'll mark it as such for now. Once we fixed that one, please re-test and yell here if you still have the problem.