I am a newcomer to Linux and Ubuntu; I was about to start the gdm environment with the command sudo start gdm but I got this message error:
start: unable to connect to Upstart: Failed to connect to socket
/com/ubuntu/upstart: Connection refused
Searching more about this issue I realised that I have to move from upstart to systemd and Upstart is no longer used by Ubuntu.
But when I type which upstart I get /sbin/upstart; while which systemctl gave /bin/systemctl.
My question is, how can I use upstart, since it is installed already on my system?