Matt,
The simplest way of running it as a system service (guessing that's what you're actually getting at?) is with a systemd unit file:
=== /etc/systemd/system/jackd.service ====
[Unit]
Description=JACK Server daemon
[Service]
Restart=always
RestartSec=5
ExecStart=/usr/bin/jackd -d alsa -r 48000 -i 2 -o 2
================
systemctl daemon-reload
systemctl restart jackd
For the 'jack_load netmanager' try adding
ExecStartPost=/bin/sleep 2
ExecStartPost=/usr/bin/jack_load netmanager -i -c
Each command needs the /full/path/to/binary with systemd :)
Cheers,
Gavin.