I was setting up a shiny new CentOS 7 EC2 instance, but when I tried to set the hostname using all of the typical Linux-y ways, none of them stuck after a reboot. It just kept going back to the default EC2 naming convention of ‘ip-172.31.x.x’. Since I am still getting used to CentOS 7 and all of the stuff they changed from 6, I figured it was a CentOS 7 thing. Not so…