Security Enhanced Linux (SELinux).
For the longest time, I've always considered SELinux a bit of a PITA, in large part because I didn't take the time to learn anything about it. It was always spitting out these annoying error messages, and keeping things from working properly. Anytime I installed/reinstalled Fedora on a machine, disabling SELinux was usually the first thing I did.
I decided it was about time I changed that and learned how to use SELinux properly.
At Flock to Fedora this past weekend, two of the talks were on SELinux: SELinux for Mere Mortals and What's New in SELinux. On top of the smattering I picked up on my own by following the troubleshooting prompts provided by
sealert(1), it was enough to make the light bulb in my head start to glow dimly. Still lots more to figure out, but it's starting to make a little more sense to me now.