We have installed some systemd stuff on our Ubuntu 14.04 but we are still using the old upstart as init system.
The postinst script will try to use systemctl to enable the wazuh agent if the systemd directory /run/systemd/system exists:

This call fails:

# systemctl enable wazuh-agent
Failed to issue method call: No such file or directory

Could we add another test to check if we still run with upstart?
Something like:

if [ -d /run/systemd/system ] && [[ ! `/sbin/init --version 2>/dev/null` =~ upstart ]]; then