What to do when you see the dreaded "Call to undefined function filter_var()" error message in your Apache logs. It's actually easier that it sounds but I recommend matching the version of the PHP source you download to that installed from your distro's official package.
How to configure password complexity on Redhat Linux machines (and its derivatives). After playing with it for a while, I'd call this a best practice because it requires all of the different character classes but doesn't give you bonus points for using any one (i.e., you have to use them all, but they could the same insofar as character scoring is concerned).
github repo for a script that sets up openvpn vpn on debian, ubuntu, centos, and arch linux. Interactive, will ask you questions used to generate configuration settings. tool utility network vm vps privacy security