How can I tell which init system Ansible runs when I use the "service" module?

Question

From the Ansible documentation, the service module:

Controls services on remote hosts. Supported init systems include BSD init, OpenRC, SysV, Solaris SMF, systemd, upstart.

For a given machine, how can I tell which init system Ansible is using? A system may have init and systemd on it, for example.

Answer 1

The init system on a host is available as Ansible fact ansible_service_mgr.

Answer 2

Let's look into the modules' code:

Inside def main()::

# Find service management tools
service.get_service_tools()

Then to class LinuxService(Service): and to def get_service_tools(self):

    # Locate a tool to enable/disable a service
    if check_systemd():
        # service is managed by systemd
        ...
    elif location.get('initctl', False) and os.path.exists("/etc/init/%s.conf" % self.name):
        # service is managed by upstart
        ...
    elif location.get('rc-service', False):
        # service is managed by OpenRC
        ...
    elif self.svc_initscript:
        # service is managed by with SysV init scripts
        ...

I've cut some code, but this snippet should answer your question: what system Ansible is likely to choose if there are many.

Systemd is the first one to search, then upstart, etc...