> I wouldn't be against systemd if it were just an init system. The problem is that it's not. That's the end of my argument.
All of systemd's functionality, as far as I'm concerned, is rationally motivated by wanting to orchestrate and instrument system startup in a sensible way. What functionality do you think systemd should not have that it has today? What is a better way of achieving the result provided by that functionality?
If your perspective is that you don't care about that functionality or the related user experience, and so all of its complexity is dead weight to you, OK. That makes sense. But as a software engineer and system administrator, I find the features extremely useful, and I think many other people do too. That's why systemd has been adopted by major distributions.
I wrote a comment earlier [1] about systemd that reviews Russ Allbery's analysis of systemd [2], from when Debian was evaluating switching to systemd and upstart. Russ's comment reviews a number of different systemd functions, such as its integrated journal, and then explains the pros and cons of each. Russ even said:
Integrated daemon status. This one caught me by surprise, since the
systemd journal was functionality that I expected to dislike. But I was
surprised at how well-implemented it is, and systemctl status blew me
away. [lots more details in linked comment]
[1]
https://news.ycombinator.com/item?id=13387989 [2]
https://lists.debian.org/debian-ctte/2013/12/msg00234.htmlSure, you could argue an init system "shouldn't" have an integrated journal (for example), but then you'd lose the clear benefits that Russ outlines. You wouldn't achieve the same benefits or user experience. Similarly, systemd's configuration-driven approach to service definition makes it possible to employ a wide variety of standard configuration options across all services. From my previous comment:
> I can launch my service at the appropriate time during boot with configuration as simple as:
[Unit]
Description=Demo service
[Service]
Type=forking
ExecStart=/usr/sbin/my-daemon
> Now let's say that I didn't author this daemon, but I'd like to run it with a private network, private temp folder, or a private /dev namespace. Or perhaps the daemon needs to run as root, but I want to drop all capabilities it doesn't need. It's as simple as adding these lines to the service's configuration:
PrivateTmp=yes
PrivateDevices=yes
PrivateNetwork=yes
CapabilityBoundingSet=CAP_NET_BIND_SERVICE
> The fact that systemd supports these configuration options means that there's a simple and standard way to employ them with any service. The service itself doesn't need to support them, and needn't complicate its own daemonization logic to do so correctly. Indeed, I don't need to trust the service to daemonize or drop capabilities, since I can tell the init system do that before launching the service.
> I can drop capabilities with CapabilityBoundingSet=, or limit resource usage with CPUSchedulingPriority=, IOSchedulingPriority=, etc. I could even tell systemd to open the listening socket for me so the service doesn't need CAP_NET_BIND_SERVICE! Moving these options into the init system makes a ton of sense, because it gives administrators the ability to employ these features from outside applications, not just by enabling them within applications that bother to explicitly support them via command line arguments. Systemd better encourages the principle of least privilege: if a system daemon does not need the ability to "ptrace" other processes, or bind to ports <1024, then as the administrator I can take those away with CapabilityBoundingSet= in the unit file. Chrooting the service is as easy as RootDirectory=. This is a huge step forward compared to the world where every service must be relied upon to expose these settings, and must be trusted to implement them correctly.