Hacker News Reader

Comment by kaba0 | Hacker News Reader

> It increases boot times

Is it really the case? On desktops it is significantly faster than all the other alternatives. Of course if you do know your hardware there is no need for discovering stuff and the like, but I don't know. Would be interested in real-life experiences because to me systemd's boot time was always way faster than supposedly simpler alternatives.

View on HN

When Arch Linux switched to systemd, my laptop (with an HDD) boot times jumped from 11 seconds to over a minute. That 11 seconds was easy to achieve in Arch’s config by removing services from the boot list and marking some of the others as supposed to be started in parallel without blocking others. After the switch to systemd there was no longer a such a simple list in a text file, and systemd if asked for the list would produce such a giant graph that I had no energy to wade through it and improve things.

Later, when I got myself a laptop with an SSD, I discovered that what my older Arch configuration could do on an HDD is what systemd could do only with an SSD.

Arch changed to systemd in 2012, at which point systemd was 2 years old. It surely had quite a few growing pains, but I don't think that's representative of the project. In general it was the first init system that could properly parallelize, and as I mentioned, it is significantly faster on most desktop systems than anything.

it was only faster if you started with bloated redhat systems to begin with. but yes, it was the beginning of parallelism on init...

but the "faster boot" you're remembering are actually a joke at the time. since the team working on it were probably booting vms all the time, the system was incredible aggressive on shutdown and that was the source of it. something like it reboots so fast because it just throws everything out and reboot, or something. i don't really care much for the jokes but that was why everyone today remembers "systemd is fast".

It mandates strict session termination, unlike the unsustainable wild west approach of older Unix systems. Proper resource deallocation is crucial for modern service management. When a user exits without approval of "lingering user processes," all their processes should be signaled to quit and subsequently killed.

i think the "unsustainable wild west" of sending sigterm, waiting and sending sighup was very good because it was adaptable (you were on your own if you had non standard stuff, but at least you could expect a contract)

Nowadays if you start anything more serious from your user session (e.g. start a qemu vm from your user shell) it will get SIGHUP asap on shutdown, because systemd doesn't care about non service pids. but oh well.

...which is where the jokes about "systemd is good for really fast reboots" came from mostly.

The old way has literally no way to differentiate between a frozen process and one that just simply wants to keep on running after the session's end, e.g. tmux, screen.

It's trivial to run these as a user service, which can linger afterwards. Also, systemd has a configurable wait time before it kills a process (the "dreaded" 2 mins timer is usually something similar)

which was fine for everything that didn't need a watchdog. systemd on the other hand still lacks most common usecase and people bend over backwards to implement them with what's available. ask distro maintainers who know the difference between the main types of service files...

> In general it was the first init system that could properly parallelize

I'm not sure what you mean by "properly" but didn't initng and upstart (and probably some others I can't recall) do the parallel stuff before systemd?

I switched to systemd when Arch switched and from the get go, it was massively easier to parallelise with systemd than with the old system and that was with an HDD.

Systemd already parallelises by default so I don't know what insanely strange things you were doing but I fail to see how it could bring boot time form 11s to 1 minute. Also, it's very easy to get a list of every services enabled with systemctl (systemctl list-unit-files --state=enabled) so I don't really know what your point about a giant graph is.

Running things in parallel isn't going to make the disk faster... with a HDD I'd think it is actually even more likely to make the disk slower.

We don’t have to talk in hypotheticals here. Booting time benchmarks from the time systemd was released are everywhere and showed shorter boot times. It was discussed ad nauseam at the time.

I mean, this anecdote only tells us that if something is configured poorly it will behave poorly.

If you're working in the embedded space it's surely worth a little bit of time to optimize something like this.

Reply on news.ycombinator.com