After installing maas 0.1+bzr1264+dfsg-0+1264+133~ppa0~quantal1 dbus and avahi-daemon are not started causing this error in /var/log/apache2/error.log
eNotFound: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] mod_wsgi (pid=10965): Target WSGI script '/usr/share/maas/wsgi.py' cannot be loaded as Python module.
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] mod_wsgi (pid=10965): Exception occurred processing WSGI script '/usr/share/maas/wsgi.py'.
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] Traceback (most recent call last):
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/share/maas/wsgi.py", line 30, in <module>
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] start_up()
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/maasserver/start_up.py", line 59, in start_up
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] inner_start_up()
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/maasserver/start_up.py", line 81, in inner_start_up
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] setup_maas_avahi_service()
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/maasserver/maasavahi.py", line 52, in setup_maas_avahi_service
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] service.publish()
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/maasserver/maasavahi.py", line 44, in publish
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] self.service.publish()
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/maasserver/zeroconfservice.py", line 44, in publish
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] bus = dbus.SystemBus()
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/dbus/_dbus.py", line 194, in __new__
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] private=private)
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/dbus/_dbus.py", line 100, in __new__
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 122, in __new__
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
[Fri Oct 12 00:38:23 2012] [error] [client 10.98.0.13] DBusException: org.freedesktop.DBus.Error.FileNotFound: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory
Restarting both services and apache2 makes the web ui work again.
I routinely see these problems when running tests in a dev branch, depending on where I am. The problem seems to be that Avahi may decide to exit after starting if it sees that it's not on the right kind of network.