uinit (think of "micro init", "user init" or "you init") is a simple process controller. It is designed after the old UNIX /sbin/init (or just init) and I started it out of curiosity when I read about systemd in Debian some years ago. My question was what it would take to write something that works similar to init. Later I found some interesting use cases.
Here's an example to show what uinit is.
smbd::restart:/usr/sbin/smbd --foreground nmbd::restart:/usr/sbin/nmbd --foreground sshd::re,helper:/path/to/sshd-helper start
would start three services: smbd, nmbd and sshd. That's also what you can get from systemd (with three unit files) but it's just as an example for illustration.
Here is another. This uinit.tab starts the services dhcpd and apd and both create a W-LAN hotspot on your Pi.
dhcpd:::dnsmasq -k -i wlan0 -F 192.168.1.11,192.168.1.55,255.255.255.0,24h apd::restart:$THIS apd ex1::exit:$THIS exit
There are two interesting things (which you cannot fully see in the example lines but see wlan-hotspot for the full script):
$THISdoes some "magic". There is no such thing as an apd service (or an ex1 handler to exit from the hotspot). Instead, this is implemented as some shell script code, which is bundled with everything else (like uinit's configuration file) into a single shell script.
ExecStartfrom a systemd service unit or another uinit.