How to filter SSH connections with hosts.allow on Rocky Linux / CentOS 8

The TCP Wrappers suite of programs is no longer included in RHEL 8, meaning the hosts.allow/deny files no longer exist nor work. This makes quick filtering SSH connections per IP address a bit more difficult as it requires configuring the firewall.

Luckily, the tcp_wrappers package is still available in the EPEL repository even for versions 8 so the previous functionality can be restored, albeit with some additional steps.

How to play sounds (or run anything) on startup and shutdown with Raspbian

The Raspberry Pi is very handy for fun projects, and sometimes these projects require running specific events (like playing a sound) on startup or shutdown, or even in both instances – for an interactive machine that reacts to user input and presence, for example.

Sounds on startup and shutdown can also be used as a means of confirming those specific actions taking place – startup is complete and shutdown is taking place (and will complete in a very short while).