If you use Zabbix to monitor your servers you may want to monitor systemd services with it especially if you have some custom services.

These simple checks were enough for me:

systemd.unit.is-active[<unit name>]  # 1 if unit is active, 0 if inactive
systemd.unit.is-failed[<unit name>]  # 1 if unit if in failed state, 0 if not
systemd.unit.is-enabled[<unit name>] # 1 if unit is enabled, 0 if not

It's very simple. Just place userparameter_systemd.conf to your zabbix config dir (usually /etc/zabbix_agentd.conf.d) with the following content:

# checks to determine if specified unit is active, failed or enabled
UserParameter=systemd.unit.is-active[*],systemctl is-active --quiet '$1' && echo 1 || echo 0
UserParameter=systemd.unit.is-failed[*],systemctl is-failed --quiet '$1' && echo 1 || echo 0
UserParameter=systemd.unit.is-enabled[*],systemctl is-enabled --quiet '$1' && echo 1 || echo 0