Documentation for SystemD

Add documentation references for SystemD .service files

Improved documentation

Not all services are well known, or well documented. The on-call personnel may not be the one responsible for the architecture or the day-to-day operations for that server.

You don’t need to edit the original unit file, you can add a drop-in file in /etc/systemd/system/<yourservice>.d/<something>.conf:

# mkdir /etc/systemd/system/mystery.service.d
# cat > /etc/systemd/system/mystery.service.d/documentation.conf
[Unit]
Documentation=https://wiki.corp.example.org/SomeClient/CommonFailures \
  https://www.enterpricy.example.org/Documentation/ \
  man:mysteryd(8) \
  file:///opt/mystery/doc/index.html
^D

The content of the “Documentation=” directive is visible when running “systemctl status servicename”. This helps your on-call person, when the alarm goes off, to figure out what is wrong, and how to fix it. Add your own service documentation, and a link to the upstream documentation.

The output will look like this:

root@turbotape:~# systemctl status mystery.service
● mystery.service - MYSTERY Scheduler
   Loaded: loaded (/lib/systemd/system/mystery.service; enabled; vendor preset: enabled)
  Drop-In: /etc/systemd/system/mystery.service.d
           └─documentation.conf
   Active: active (running) since Mon 2016-11-28 06:25:01 CET; 6h ago
     Docs: man:mysteryd(8)
           https://wiki.corp.example.org/SomeClient/CommonFailures
           https://www.enterpricy.example.org/Documentation/
           man:mysteryd(8)
           file:///opt/mystery/doc/index.html
 Main PID: 10015 (mysteryd)
      CPU: 251ms
   CGroup: /system.slice/mystery.service
           ├─10015 /usr/sbin/mysteryd -l
           └─10218 /usr/lib/mystery/notifier/dbus dbus://

Nov 28 06:25:01 turbotape systemd[1]: Started MYSTERY Scheduler

Source : https://www.redpill-linpro.com/sysadvent/2016/12/22/systemd-at-3am.html