SystemD Quickstart

Varokas Panusuwan

• 2 min read
SystemD Quickstart

A quite handy framework built-in to most Linux distro. SystemD helps in setting up a process that restarts itself on boot, and when it crash. This is what many packages do when apt-installed.

Doing it by hand is not complicated. But I couldn't find a single quickstart source to refer to. This is my public tl;dr notes in setting up systemd that should match most needs.

Let's say we are setting up homebridge. Replace that name with your service.

The Service File

Describe the service, where's the executable, who's the user that should run it as.

file: /etc/systemd/system/homebridge.service

[Unit]
Description=HomeBridge server # A description 
After=syslog.target network-online.target

[Service]
Type=simple
User=pi # A username to run this service as
EnvironmentFile=/etc/default/homebridge #Environment Variable for the service. This is a separate file creating below

# See comments below for more information
ExecStart=/usr/bin/homebridge $HOMEBRIDGE_OPTS #As you'd type in command line. $HOMEBRIDGE_OPTS is from the EnvironmentFile defined below
Restart=on-failure
RestartSec=10
KillMode=process

[Install]
WantedBy=multi-user.target

The Environment File

Many processes are controlled by environments variable. It is usually better to separate those out as a file.  

file: /etc/default/homebridge

HOMEBRIDGE_OPTS=-U /var/lib/homebridge
# DEBUG=*

Startup and Logging

A 3 step dance.

# This is to load any changes
# Do this everytime you a file content is changed
sudo systemctl daemon-reload

# Make the service restart every boot
sudo systemctl enable homebridge

# Start up the service
sudo systemctl start homebridge

To see if the service really started up corrrectly.

$ sudo systemctl status homebridge

● homebridge.service - Node.js HomeKit Server
   Loaded: loaded (/etc/systemd/system/homebridge.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2019-05-25 17:56:31 BST; 5s ago
 Main PID: 13572 (homebridge)
   CGroup: /system.slice/homebridge.service
           └─13572 homebridge

To see the logs printed out by the service to system out

$ sudo journalctl -u homebridge

May 25 17:56:31 raspberrypi systemd[1]: Started Node.js HomeKit Server.
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] Loaded config.json with 1 accessories and 0 platforms.
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] ---
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] Loaded plugin: homebridge-webos-tv
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] Registering accessory 'homebridge-webos-tv.webostv'
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] ---
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] Loading 1 accessories...
May 25 17:56:34 raspberrypi homebridge[13572]: [2019-5-25 17:56:34] [TV] Initializing webostv accessory...

References