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Why systemd is a problem for embedded Linux

kevinboone.me

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Re: Why systemd is a problem for embedded Linux

#81

Post by stefan_ »

phendrenad2 wrote: post #23

Wait so systemd is a problem for embedded Linux because... it uses 250MB of RAM? So it's only really a problem for systems where using a mainstream distro probably wouldn't even be a consideration anyway (yocto seems to be popular, as mentioned above). I'm not seeing a strong argument here. At the risk of inviting a parade of "actually, one time at band camp I saved the day with a first-gen raspberry pi zero", how ma…

Thats a weird question, every embedded system that is a consumer product will end up with limited RAM simply because less RAM is a $1 saved on the BOM. For most systems, RAM is a choice, and for many of them someone will ask at the end "how much can we get away with".

(Your WiFi router probably has 256 or 512 MB of RAM)

Re: Why systemd is a problem for embedded Linux

#82

Post by teunispeters »

If it can run X11 on a directly connected display, it's probably not embedded spaces ;). Don't take this comment too seriously, however raspberry pi is definitely at the "more desktop-like" end of the embedding pool.

As for systemd, it's an interesting set of tools, and one can if one wishes pick which ones are active in a system, if that system is complex enough to be running Linux (or other compatible OS) to begin with.

Re: Why systemd is a problem for embedded Linux

#83

Post by m463 »

I think what he's running into is "the unix philosophy".

It is basically about small tools, limited in scope, that solve a problem surgically and comprehensively. They work together by mixing and matching to solve the problem.

systemd is sort of like if microsoft word took on system init. In the beginning it was small, but now it is web based and does videoconferencing.

I don't know, it is sort of like busybox, replacing other system components in a limited Minimum Viable Product way, but more like limited function, not limited resources.

Re: Why systemd is a problem for embedded Linux

#84

Post by hansvm »

BenjiWiebe wrote: post #71
hansvm wrote: post #40

Not really embedded, but one of the easier classes of wins I've had over the years is moving prod servers to a non-systemd Gentoo. Random (rare) 200ms latency spikes and whatnot just disappear, and the system jitter drops down to the tens of microseconds range, significantly improving the qualitative performance of basically every piece of software I care about.

Did you ever dig in to see why that changed? I'm surprised that in a steady-state (not booting or restarting services) systemd/not-systemd would have an impact.

A little bit. The tldr; is that there are a lot of periodic activities including log rotation, automatic updates, time syncing, waking up to check if such things were currently needed, .... Those are generally nice (aside from automatic updates, which are sometimes good but I think usually more harmful than whatever they're fixing), but systemd doesn't know anything about what my userspace demands on the hardware are, and it's generally happy to hog system resources if it doesn't do so for long. For anything quasi-realtime, I can certainly hunt down and squash everything systemd is running at the wrong time, but in practice it's much easier to install something else, ensure no processes are running other than the ones I care about, and move those concerns to userspace.

Re: Why systemd is a problem for embedded Linux

#85

Post by fn-mote »

dcsommer wrote: post #77
transpute wrote: post #16

OpenEmbedded/Yocto, Devuan and Gentoo provide multiple init systems. systemd CVEs: https://ubuntu.com/security/cves?package=systemd&limit=100 Rust PoC: https://github.com/KillingSpark/rustysd > Rustysd is a service manager that tries to replicate systemd behaviour for a subset of the configuration possibilities. It focuses on the core functionality of a service manager, not requiring to be PID1 (aka init process).. c…

How many systemd CVEs are memory or thread safety related?

I can't tell if this is rhetorical but... it looks like quite a few on the list. (Note: the CVE list is long but it looks inflated / full of not-serious issues.)

* CVE-2022-3821 : off by one error leading to buffer overflow

* CVE-2022-2526 : use after free

* CVE-2021-33910 : "Memory Allocation with an Excessive Size Value" (not sure if this qualifies... not interested enough to read the source)

Re: Why systemd is a problem for embedded Linux

#86

Post by oguz-ismail »

m463 wrote: post #83

I think what he's running into is "the unix philosophy". It is basically about small tools, limited in scope, that solve a problem surgically and comprehensively. They work together by mixing and matching to solve the problem. systemd is sort of like if microsoft word took on system init. In the beginning it was small, but now it is web based and does videoconferencing. I don't know, it is sort of like busybox, repla…

> systemd is sort of like if microsoft word took on system init. In the beginning it was small, but now it is web based and does videoconferencing

And it's slow. Windows 11 boots in 5 seconds on my laptop, Ubuntu 22 used to take about a minute before I finally made the switch.

Re: Why systemd is a problem for embedded Linux

#87

Post by samatman »

righthand wrote: post #55
cbmuser wrote: post #39

Earlier quoted context omitted.

> How many people eat McDonalds? If you’re already starting like this it’s obvious that the following text will be non-scientific non-sense. As a reminder: There is no such thing as “healthy food” and “unhealthy food”, there is just healthy and unhealthy nutrition. Still baffles me that people think it would actually be legal to sell actual unhealthy food, i.e. poisonous food. Also, “organic food” is just a marketing…

It is legal to sell unhealthy food, ie poisonous food. Sugar is a poison, drugs are poisons. You can legally sell escolar a fish that if eaten too much is poisonous. What is poisonous food? You can sell plastic that breaks down into the environment and people are drinking it in water, eating it in fish. Is that legally sold poisonous food?

Sugar is not, in fact, a poison.

As for drugs:

> Alle Dinge sind Gift, und nichts ist ohne Gift; allein die Dosis macht, dass ein Ding kein Gift ist.

  - Paracelsus, 1538
https://en.wikipedia.org/wiki/The_dose_makes_the_poison

Re: Why systemd is a problem for embedded Linux

#88

Post by TacticalCoder »

cozzyd wrote: post #56

I run systemd-based Debian just fine on 512 MB RAM BeagleBoneBlack SBCs with 4GB emmcs. Now emacs, that's a problem due to the large install size.

> Now emacs, that's a problem due to the large install size.

I was running Emacs on a 486 with something like 16 MB of RAM. Don't remember the HDD size.

The Emacs executable I built from source is about 28 MB. Honestly I don't know what else is needed besides that executable that'd be really big.

Is it really that problematic that it wouldn't work with 512 MB of RAM and 4 GB of storage?

Re: Why systemd is a problem for embedded Linux

#89

Post by dralley »

oguz-ismail wrote: post #86
m463 wrote: post #83

I think what he's running into is "the unix philosophy". It is basically about small tools, limited in scope, that solve a problem surgically and comprehensively. They work together by mixing and matching to solve the problem. systemd is sort of like if microsoft word took on system init. In the beginning it was small, but now it is web based and does videoconferencing. I don't know, it is sort of like busybox, repla…

> systemd is sort of like if microsoft word took on system init. In the beginning it was small, but now it is web based and does videoconferencing And it's slow. Windows 11 boots in 5 seconds on my laptop, Ubuntu 22 used to take about a minute before I finally made the switch.

That almost certainly has little to do with systemd itself, and more to do with which services are enabled on boot.

Re: Why systemd is a problem for embedded Linux

#90

Post by iluvcommunism »

I like systemd sometimes. Other times it confuses me. Particularly the way cgroups work. The way splicing works. Why oracle mem usage is still uncontrollable when I set user splice restrictions. Idk, I’m still learning it. I don’t like the terminology it uses sometimes too like “snapshot.” When I first read about systemd snapshot I was like oh cool you can snapshot the system. No. Also some esoteric things it supposedly supports don’t work sometimes. I find the idea of systemd targets and fstab having anything to do with each other anathema. Idk.
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