Long story short, I got tired of Windows 10 a couple of weeks ago. The performance on my five year old dual core laptop was less than satisfying, and I wanted to get more out of my laptop. Enter FreeBSD.
I started out with 10.2-RELEASE and KDE4. It had some annoying issues, particularly in switching to a virtual console locking up the system. It didn't take long for me to decide there's not much reason to stay on -RELEASE, so I moved to -CURRENT. This background comes in now because it may be relevant in future posts about FreeBSD exploits.
Anywho! In my weekly update to the latest -CURRENT && rebuilding world, I started running mergemaster. I was in a little bit of a hurry and managed to nuke my /etc/group and overwrite /etc/passwd. Cue a good six minutes figuring out an easy way to restore all of the passwords and groups I lost, until I came across a post mentioning that there should be backups of my previous revision in /var/backups. Restored all, happiness returns, thank you internet.