Create the shairport-sync user and shairport-sync group, create the service and link it to run.
In a terminal:
sudo groupadd shairport-sync
sudo useradd -G shairport-sync shairport-sync
sudo nano /etc/runit/sv/shairport/run
Add the following lines:
#!/bin/sh
sv check avahi-daemon > /dev/null || exit 1
exec chpst -u shairport-sync shairport-sync
and make it executable by
sudo chmod +x /etc/runit/sv/shairport/run
and enable it after by linking:
sudo ln -s /etc/runit/sv/shairport /run/runit/service
and finally check it's status with the following:
sudo sv status shairport
ps aux | grep shairport
Awaiting your feedback.