[Jack-Devel] How to use jackd as a 'system-wide' server?

[Ruslan N. Marchenko]

Am Donnerstag, den 10.05.2018, 15:50 +0200 schrieb Christophe Lohr:
> 
> Unfortunately I still have errors when I place a call to this
> asterisk
> channel:
>     ../..
>     -- Executing [6000 at default:5] JACK("SIP/6007-00000003", "") in
> new stack
> [May 10 13:34:25] NOTICE[2899][C-00000003]: app_jack.c:192
> log_jack_status: Client Open Status: Failure, Server Error
>   == Spawn extension (default, 6000, 5) exited non-zero on
> 'SIP/6007-00000003'
>   ../..
> 
> How can I get more log messages from the jackd server?
> 
Long time ago I was using Jack2 as a system-wide service on HTPC
running Ubuntu using following upstart script
////
start on runlevel [2345] or local-filesystems
stop on runlevel [!2345]
emits audio-bus

console log

env HOME=/root

pre-start script
if [ ! -f /run/dbus/.env ]; then
  eval `dbus-launch --auto-syntax`
  echo "export DBUS_SESSION_BUS_PID=$DBUS_SESSION_BUS_PID" >
/run/dbus/.env
  echo "export DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS" >>
/run/dbus/.env
  chmod 600 /run/dbus/.env
fi
end script

post-start script
. /run/dbus/.env
jack_control start
if [ -f /etc/default/jackd ]; then
  awk '/^[esdri]/{system("jack_control "$0)}' /etc/default/jackd
  awk '/^ /{system("jack_load "$0)}' /etc/default/jackd
  awk '/^>/{  
        system("jack_connect "$2":capture_1 "$3":playback_1");
        system("jack_connect "$2":capture_2 "$3":playback_2");
  }' /etc/default/jackd
fi
end script

post-stop script
. /run/dbus/.env
if [ -f /etc/default/jackd ]; then
  awk '/^ /{system("jack_unload "$1)}' /etc/default/jackd
fi
jack_control exit
end script
\\\\
upstart is now a history but the principle should be the same I guess.
systemd allows you even to have user-level session initiation, so
should be much mroe flexible in this regard.

The key point back then was /run/dbus/.env - that one allowed me to
join same DBus session where JackDBus was spawned.

Then each application which was going to use Jack should be started
with .env file loaded populating the environment variables.

You can ignore /etc/default/jackd - that one was my custom recipe file
which pre-loaded required modules and made required connections at the
early start.