What exactly does systemd do?

Linux@lemmy.ml – 171 points – 11 months ago

I am a Linux user, but I don't really know how most things work, even after years of casual use on my Main, I just started getting into Devuan and wondered then, what exacly does systemd do that most distros have it? What even is init freedom? And why should I care?

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This is a good post.

As for why people don't like systemd, it follows the kitchen-sink approach to software and does a lot of things at once.

For people new to Linux I just want to point out - for better or for worse this goes against the Unix philosophy.

Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface.

One thing that people miss - either out of ignorance, or because it goes against the narrative - is that systemd is modular.

One part handles init and services (and related things like mounts and sockets, because it makes sense to do that), one handles user sessions (logind), one handles logging (journald), one handles networking (networkd) etc etc.

You don't have to use networkd, or their efi bootloader, or their kernel install tool, or the other hostname/name resolution/userdb/tmpfiles etc etc tools.

Could one argue that a monolithic kernel such as the Linux kernel also goes against that principle?

Technically the Linux kernel is just an interface with lots of modules

So is systemd. It is definitely modular and I think it has multiple interfaces as well. I’m not sure if you have configure systemd modules like GRUB does.