I am often confused by the exact init system being used on a Ubuntu system since there are 3 of them: sysvinit, upstart and systemd. And it's not rare to see packages including multiple scripts for different init systems. I'm wondering how these init systems coexist in Ubuntu right now. Since newer versions of Ubuntu have shifted from upstart to systemd, I'm interested in when we can completely forget upstart. I'm currently using 14.04 LTS. Should I upgrade to 16.04 LTS if I want to stick with systemd?