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If you’re an intermediate or advanced Linux user or sysadmin, you might have felt an odd fascination with the myth of systemd. I invite you to this deep dive into systemd's nuts and bolts. I'm not gonna beat around the bush: It's a hairy business, it will be hard, but I promise juicy and satisfying rewards if you keep it up.
Let’s start by uncovering the “D” of systemd, the secret sauce that doesn't get the love it deserves: D-Bus.
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Warning: This guide starts from systemd’s internals, and only towards the end reaches the user-facing interface. By this we aim for a deeper, “bottom-up,” solid understanding. Readers in urgent need of getting familiar with systemd are advised to look elsewhere (but feel free to skim and look at the pretty visual graphics, whose likeness is yet to be replicated elsewhere by any other systemd guide).
Don’t Miss D-Bus on This One
So, what is this D-Bus thing? D-Bus (short for “Desktop Bus”) is a high-level message-passing mechanism for Inter-Process Communication (IPC).