What creates /var/run/dbus/system_bus_socket?

Martin Pauly pauly at hrz.uni-marburg.de
Mon Dec 26 06:43:30 PST 2011

Hi everyone,

hope you're enjoying x-mas ...
I have run into an awkward problem:
It all started when I thoroughly screwed up one of my Ubuntu
Natty machines. I did this by adding (mistakenly, of course)
Debian Squeeze repositories to apt/sources.list and running
apt-get upgrade. This left me with a mess of SysV-Init related
Debian Stuff that had mangled the Upstart-based Ubuntu-packets.
Normally, this would have been the point to reinstall.
But rather, I opted for a repair -- isn't Linux just a
big gearbox where you can exchange every single part?
With a lot of apt-get reinstall and dpkg-reconfigure,
I've actually come quite close now to my goal of
repairing things. But one problem keeps puzzling me:
Unlike on my working Natty machine, the essential
is destroyed in every boot cycle. Only calling
   dpkg -r dbus
   apt-get install dbus
will make it reappear. As soon as it is there,
gdm comes on, and work can begin.

In contrast, apt-get reinstall dbus won't work,
nor can you pack a Unix Domain socket into
some tar file. Curious what was going on,
I examined Ubuntu's dbus debian package,
but only found some seemingly systemd-related
configuration hints for that socket in the
control branch. That is probably left from
the "original" debian package before it was
migrated to Ubuntu. Running the above commands
under strace -f confirmed my suspicion: Not
a single line in the output pointing to socket
creation. So the remove-install cycle must provoke
some indirect effect, ie trigger some other event
that creates /var/run/dbus/system_bus_socket.

What the hell is that effect?

Thx for any hints

   Dr. Martin Pauly     Phone:  49-6421-28-23527
   HRZ Univ. Marburg    Fax:    49-6421-28-26994
   Hans-Meerwein-Str.   E-Mail: pauly at HRZ.Uni-Marburg.DE
   D-35032 Marburg

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