Comment 2 for bug 674704

On a hunch, I decided to try testing for an undocumented dependency between udev and dbus.

Installing dbus failed to fix udev hang upon start.

# dpkg-query -l dbus udev
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Description
+++-================-================-================================================
un dbus <none> (no description available)
ii udev 151-12.3 rule-based device node and kernel event manager

# apt-get install dbus
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  dbus-x11
Recommended packages:
  consolekit
The following NEW packages will be installed:
  dbus
0 upgraded, 1 newly installed, 0 to remove and 1 not upgraded.
Need to get 189kB of archives.
After this operation, 618kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu/ lucid/main dbus 1.2.16-2ubuntu4 [189kB]
Fetched 189kB in 1s (157kB/s)
debconf: delaying package configuration, since apt-utils is not installed
Selecting previously deselected package dbus.
(Reading database ... 31546 files and directories currently installed.)
Unpacking dbus (from .../dbus_1.2.16-2ubuntu4_i386.deb) ...
Processing triggers for man-db ...
Setting up dbus (1.2.16-2ubuntu4) ...
Adding system user `messagebus' (UID 107) ...
Adding new group `messagebus' (GID 111) ...
Adding new user `messagebus' (UID 107) with group `messagebus' ...
Not creating home directory `/var/run/dbus'.
dbus start/running, process 4833

# status udev
udev start/running, process 348
# stop udev
udev stop/waiting
# status udev
udev stop/waiting
r# start udev
Terminated
# status udev
udev start/starting