So it turns out that setting your AWS EC2 server's hostname to be persistent across reboots is a surprising pain in the ass, at least with my usual OS of choice - RedHat/CentOS Linux. If you're like me, setting a hostname is the sort of trivial non-task that at this point you really feel like you dont need to RTFM to figure out. You know about `hostnamectl set-hostname`. You've tried `nmcli general hostname`. You've manually set /etc/hostname. None of its persists past a reboot. Which can make life very difficult for those planning to use EC2 for email or dozens of other tasks. Here's how to do it the right way, the first time. I'll also describe some circumstances that setting your own hostname will break things, and why its such a hassle to get this done in AWS in the first place. Amazon relies on cloud-init to manage a variety of initialization tasks for its cloud servers; cloud-init was originally built to support Ubuntu images , but it is now used fo...