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

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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

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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).