Very good point about Docker giving you a false idea about being to able to run old images on new OSs, which only real VMs can do. CentOS 6 isn't even old - it'

Very good point about Docker giving you a false idea about being to able to run old images on new OSs, which only real VMs can do. CentOS 6 isn't even old - it's used all over the place, and people hang on to it because it's systemd-free.