D-Bus Service Activation through Upstart

[Scott James Remnant]

With the most recent upload of D-Bus (1.4.1-0ubuntu2) it is now possible 
for D-Bus services to be activated via Upstart.

For example, let's say we wanted to convert the existing 
com.ubuntu.LanguageSelector service over.  First you need to edit the 
D-Bus service file:

/usr/share/dbus-1/system-services/com.ubuntu.LanguageSelector.service

         [D-BUS Service]
         Name=com.ubuntu.LanguageSelector
         Exec=/usr/lib/language-selector/ls-dbus-backend
         User=root
+      UpstartJob=y

(I've marked the new UpstartJob=y line you need to add)

Next create an Upstart Job for it

/etc/init/LanguageSelector.conf

     start on dbus-activation com.ubuntu.LanguageSelector
     exec /usr/lib/language-selector/ls-dbus-backend

And you're done.


Obviously it gets much more useful when you add other Upstart features 
into the mix; D-Bus activated services are just Upstart jobs, so you can 
have pre-start scripts, you can have custom umasks, chroots, oom 
adjustments, etc.

And you can also put more things in that "start on" line, for example to 
start something on activation or some other event:

     start on surprise \
         or dbus-activation com.ubuntu.Example

You can use "and" here too, but be careful since that may prevent it 
from being activated more than once.  (It waits for both events each time).

Scott