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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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What exactly does systemd do? (lemmy.zip)

submitted 1 year ago by [email protected] to c/[email protected]

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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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[–] [email protected] 17 points 1 year ago* (last edited 1 year ago)

I mean to a certain degree, I can understand if people find a problem with Poetterings approach of doing things !CORRECT!. Like, systemd-resolved resolving A-records with multiple addresses ina deterministic fashion because it's not defined not to be deterministic, and because actual load balancing would be better. It's not wrong, but it's breaking everything. And it got patched after some uproar. And there are a few things like that.

But at the same time - I don't think people appreciate how hard doing process management right on linux can be, especially if the daemon to run is shitty. Like, init scripts just triggering the shutdown port on a tomcat - except the tomcat is stuck and not reacting to the normal shutdown port and now you have a zombie process and an init script in a fucked up step. Or, just killing the main process and for some reason not really removing the children, now there's zombies all over the place. Or, not trying appropriate shutdown procedures first and just killing things, "because it's easier". Or, just trying soft and "Pwease wexit Mr Pwocess" signals and then just giving up. Or having "start" just crash because there was a stale PID from an OOM killed process around. Man I'm getting anxiety just thinking about this.

And that's just talking about ExecStart and ExecStop, pretty much, which I have done somewhat correct in a few init scripts back in the day (over months of iteration of edge cases). Now start thinking about the security features systemd-analyze can tell you about, like namespaces, unmapping syscalls, masking parts of the filesystem, ... imagine doing that with the jankyness of the average init.d script. At that point I'd start thinking about rebooting systems instead of trying to restart services, honestly.

And similarly, I'm growing fond of things like systemd-networkd, systemd-timesyncd. I've had to try to manage NetworkManager automatically and jeez... Or just directly handling networking with network-scripts. Always a pleasure. Chucking a bunch of pretty readable ini-files into /etc/systemd/networkd is a blessing. They are even readable even to people rather faint on the networking heart.