Know if a systemd is really enabled or not

Question

I want to figure out if a service is enabled or not.

With the SysV Init was easy. But with systemctl status <service name> is confusing and systemd is too complex to dig in.

Specifically, I try enabling with

# systemctl enable watchdog.service

but after reboot it's gives me this status:

# systemctl status watchdog.service
● watchdog.service - watchdog daemon
   Loaded: loaded (/lib/systemd/system/watchdog.service; static; vendor preset: enabled)
   Active: inactive (dead)

But I can't understand id it's enable but something happening, or if the enable service command failed.

At any moment, starting the service manually works fine:

# systemctl start watchdog.service
# systemctl status watchdog.service
● watchdog.service - watchdog daemon
   Loaded: loaded (/lib/systemd/system/watchdog.service; static; vendor preset: enabled)
   Active: active (running) since Qua 2016-12-21 04:03:26 BRST; 2s ago
  Process: 9111 ExecStart=/bin/sh -c [ $run_watchdog != 1 ] || exec /usr/sbin/watchdog $watchdog_options (code=exited, sta
  Process: 9109 ExecStartPre=/bin/sh -c [ -z "${watchdog_module}" ] || [ "${watchdog_module}" = "none" ] || /sbin/modprobe
 Main PID: 9115 (watchdog)
   CGroup: /system.slice/watchdog.service
           └─9115 /usr/sbin/watchdog

watchdog[9115]: int=1s realtime=yes sync=no soft=no mla=24 mem=0
watchdog[9115]: ping: no machine to check
watchdog[9115]: file: no file to check
watchdog[9115]: pidfile: no server process to check
systemd[1]: Started watchdog daemon.
watchdog[9115]: interface: no interface to check
watchdog[9115]: temperature: no sensors to check
watchdog[9115]: test=none(0) repair=none(0) alive=/dev/watchdog heartbeat=none to=root no_act=
watchdog[9115]: watchdog now set to 15 seconds
watchdog[9115]: hardware watchdog identity: Broadcom BCM2835 Watchdog timer

Answer 1

systemctl status tell us the unit is in status static:

# systemctl status watchdog.service
● watchdog.service - watchdog daemon
   Loaded: loaded (/lib/systemd/system/watchdog.service; static; vendor preset: enabled)
   Active: inactive (dead)

From man systemctl:

"static" | The unit file is not enabled, and has no provisions for enabling in the "[Install]" unit file section.

This basically means there is no [Install] section in the service file and thus you cannot enable it by systemctl enable. The way to enable such unit is to pull it into a dependency chain, i.e. make it being required or wanted by other units.