This mod is a large, powerful API, which contains a variety of tools that are extremely useful to server owners, debuggers, and game/modpack creators who need a powerful, central compatibility layer which also contains several useful tools for routine tasks that can become tiresome after repeatedly having to implement them the same way for several mods.
The most notable feature in this mod is the concept of services, dynamically toggleable and reloadable daemons which can be used to apply changes to a mod's code in real-time without having to restart the server that it is running on.
If only a small portion of its functionality is used, mods should not hard-depend on minetest_systemd, but should instead support it as an optional compatibility layer.
Details on how to use the various tools and services provided by minetest_systemd, read through the readme.md file in the mod's repository.
After 2019_3_12, all updates which do not require a full server restart when transitioning from the previous release are marked with "-R". Use the command "/minetestd reload core" to apply them.