I have a laptop with Ubuntu 16.06. I am able to execute reboot command as a non-root user without sudo. How can I change this behaviour so that I am not able to run reboot without sudo? I tried checking where reboot actually points:
user:~$ which reboot
/sbin/reboot
user:/sbin$ ls -l reboot
reboot -> /bin/systemctl
But I do not know how to change systemctl behaviour.