Tiny init script in plain shell. Suitable for Docker. Handles signals and forwards them to the child processes for a clean shutdown.

myinit.sh

#!/usr/bin/env sh

# Define your services here. One line per service.
services='
    php-fpm -F
    nginx -g "daemon off;"
'

pids=""
die(){ [ -n "$pids" ] && kill $pids 2>/dev/null; wait $pids; }
trap die SIGINT SIGTERM

# Starting services
while IFS= read -r s ; do
    if [ -n "$s" ]; then
        eval "$s &" || die
        pids="$pids ""$!"
    fi
done << EE
$services
EE

# Healthchecker. Kills all services if any service goes down. Starts in a subshell.
(
while true; do
    kill -0 $pids 2> /dev/null || { die && exit;}
    sleep 2
done
) &

wait $pids