As for Linux from Scratch - This is something that's been on my radar, but without the part I'm truly interested in (learning more about SysV) then I'm less inclined to bother. I don't buy the reason of Gnome/KDE - isn't LfS all about the basics of the distro than building a fully fledged system? If it's the foundation for the other courses, but it still feels weak that it's so guided by a future GUI requirement for systemd when it's talking about building web servers and the like in a 500Mb or less as the motivation.
All the compliants I see tend to be philisophical criticism of systemd being "not unixy" or "monolithic".
But there's a reason it's being adopted: it does it's job well. It's a pleasure being able to manage timers, socket activations, sandboxing, and resource slices, all of which suck to configure on script based init systems.
People complain in website comment sections how "bloated" systemd is, while typing into reddit webpage that loads megabytes of JS crap.
Meanwhile a default systemd build with libraries is about 1.8MB. That's peanuts.
Systemd is leaps and bounds in front of other init systems, with robust tooling and documentation, and despite misconceptions it actually quite modular, with almost all features gated with options. It gives a consistent interface for linux across distributions, and provides a familar predictible tools for administators.
But it lacks any consistency. It's not a cohesive project with a vision, it's a collection of tools without any overarching idea. This is reflected in its documentation, it's an OK reference manual, but go on and try to build a full picture of system startup.
To give you concrete examples:
1. Systemd has mount units, that you would expect to behave like regular units but for mounts. Except that they don't. You can specify the service retry/restart policy for regular units, including start/stop timeouts, but not for mounts.
2. Except that you can, but only if you use the /etc/fstab compat.
3. Except that you can not, if systemd thinks that your mounts are "local". How does it determine if mounts are local? By checking its mount device.
4. Systemd has separate behaviors for network and local filesystems.
5. One fun example of above, there's a unit that fires up after each system update. It inserts itself _before_ the network startup. Except that in my case, the /dev/sda is actually an iSCSI device and so it's remote. So systemd deadlocks, but only after a system update. FUN!!!
6. How does systemd recognize network filesystems? Why, it has a pre-configured list of them: https://github.com/systemd/systemd/blob/4c6afaab193fcdcb1f5a... Yes, you read it correctly. A low-level mount code has special case for sshfs, that it detects by string-matching.
7. But you can override it, right? Nope. This list is complete and authoritative. Nobody would ever need fuse.s3fs . And if you do, see figure 1.
I can go on for a looooong time.
The iSCSI loop issue: https://github.com/systemd/systemd/issues/34164 It keeps popping up again and again and is summarily ignored.
The remote FS detection also came up multiple times, and the maintainers don't care.
How do we determine that a specific instance of a filesystem mount is "remote", or even requires a "network"? Consider that the network endpoint might be localhost, a netlink/unix/other socket, or, say, an IP address of the virtual host (practically guaranteed to be there and not truly "remote").
systemd has .mount units which are way more configurable than /etc/fstab lines, so they'd let you, as the administrator, describe the network dependency for that specific instance.
But what if all we have is the filesystem type (e.g. if someone used mount or /etc/fstab)?
Linux doesn't tell us that the filesystem type is a network filesystem. Linux doesn't tell us that the specific mount request for that filesystem type will depend on the "network". Linux doesn't tell us that the specific mount request for that filesystem type will require true network connectivity beyond the machine itself.
So, before/without investing in a long-winded and potentially controversial improvement to Linux, we're stuck with heuristics. And systemd's chosen heuristic is pretty reasonable - match against a list of filesystem types that probably require network connectivity.
If you think that's stupid, how would you solve it?
Like systemd authors do! Hard-code the list of them in the kernel, including support for fuse and sshfs. Everything else is pure blasphemy and should be avoided.
Me? I'd have an explicit setting in the mount unit file, with defaults inferred from the device type. I would also make sure to not just randomly add landmines, like systemd-update-done.service. It has an unusual dependency requirements, it runs before the network filesystems but after the local filesystems.
I bet you didn't know about it? It's a service that runs _once_ after a system update. So the effect is that your system _sometimes_ fails to boot.
> systemd has .mount units which are way more configurable than /etc/fstab lines
It's literally the inverse. As in, /etc/fstab has _more_ options than native mount units. No, I'm not joking.
Look at this man page: https://www.freedesktop.org/software/systemd/man/latest/syst... The options with "x-systemd." prefix are available for fstab.
Look for the string: "Note that this option can only be used in /etc/fstab, and will be ignored when part of the Options= setting in a unit file."
The "can only be used in /etc/fstab" systemd settings are essentially workarounds to do those things via fstab (and workaround fstab related issues) rather than depend on other systemd facilities (c.f. systemd-gpt-auto-generator). From a "what can you do in /etc/fstab without knowing systemd is working behind the scenes" point of view, then yes, systemd units are vastly more configurable.