Getting started with systemd

This document describes the simple intro of systemd, sample systemd service file for your aah application and steps to accomplish it.

systemd is an init system that provides many powerful features for starting, stopping, reload configuration and managing processes. Refer to systemd man page.

systemd consists of two main concepts:

  • A unit is a configuration file that describes the properties of the process that you’d like to run.
  • A target is a grouping mechanism that allows systemd to start up groups of processes at the same time. This happens at every boot as processes are started at different run levels.

Table of Contents

Sample systemd service file

This is aahframework.org website service file. aah application build archive extracted at location /home/aah/website.

[Unit]
Description=aahframework.org
After=network.target

[Service]
EnvironmentFile=/home/aah/env_values
User=aah
Group=aah
Type=forking
ExecStart=/home/aah/website/aah.sh start
ExecStop=/home/aah/website/aah.sh stop
Restart=on-failure

[Install]
WantedBy=multi-user.target

Steps to Configure and Enable

  • Step 1: create a service file at /etc/systemd/system/aahwebsite.service with above reference for your application.
  • Step 2: we are gonna reload it sudo systemctl daemon-reload.
  • Step 3: to enable aahwebsite.service file; execute sudo systemctl enable aahwebsite.service.
  • Step 4: congrats, you have successfully created service file.

How to Start, Stop, Restart and Status

We have successfully created a service file, let’s see how to run it. Don’t forget to replace your service filename with below example commands.

Start your application

sudo systemctl start aahwebsite.service

# OR
sudo systemctl start aahwebsite

# OR
sudo service aahwebsite start

Stop your application

sudo systemctl stop aahwebsite.service

# OR
sudo systemctl stop aahwebsite

# OR
sudo service aahwebsite stop

Restart your application

sudo systemctl restart aahwebsite.service

# OR
sudo systemctl restart aahwebsite

# OR
sudo service aahwebsite restart

Status of your application

sudo systemctl status aahwebsite.service

# OR
sudo systemctl status aahwebsite

# OR
sudo service aahwebsite status


You will get similar output:

● aahwebsite.service - aahframework.org
   Loaded: loaded (/etc/systemd/system/aahwebsite.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2017-09-22 17:05:20 PDT; 6s ago
  Process: 16623 ExecStart=/home/aah/website/aah.sh start (code=exited, status=0/SUCCESS)
 Main PID: 16629 (aahwebsite)
    Tasks: 6
   Memory: 8.4M
      CPU: 748ms
   CGroup: /system.slice/aahwebsite.service
           └─16629 /home/aah/website/bin/aahwebsite -profile=prod

Sep 22 17:05:20 cn01-sfo.aahframework.org systemd[1]: Starting aahframework.org...
Sep 22 17:05:20 cn01-sfo.aahframework.org aah.sh[16623]: aahwebsite started.
Sep 22 17:05:20 cn01-sfo.aahframework.org systemd[1]: Started aahframework.org.

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