Hi Len,
i am using ubuntu studio.
the pc i refer to is used for audio processing and routing primarily - it is a jack client server.
so without any user intervention apart from powering it ON , it gets audio through ethernet from the jack master, processes it and sends it out through its local soundcards.
on occasions I want to log on and use this computer for local audio capturing and / or playback. so jack would ideally run independent of a user session. Having said that, I usually don't need to log out and back in, I tend to lock the system as I am a single user. no need to deal with multiple user case now.
I use a locally compiled jack2 version without dbus support because I had a version mismatch between windows and linux jack.
some audio applications (namely calf) need an X server so in my custom startup scripts I start a vnc session as well.
The problem as I understand it is that after log on, pam.d elevates logged in user's privileges to access hardware. The main problem is that alsa_(in|out) is can not grab the local soundcards... and I do not know what could be the conflict. people over at jack-devel mailing list said it could bea number of things like pulseaudio or lightdm....
there seems to be a conflict or ideologies because some one suggests I make a system init script and another says jack is not designed to run as a system service.
Personally, I think that jack is indeed not designed as a system service, but I could be wrong. what is more a jack run as root, would never be available to applications that I would start as a user. is that so?
I think I replied to everything :)