[jalgos_eminator]

OpenWRT is VERY sensitive to firmware size. I developed for a device with 16 MB flash that had both a normal (~11 MB) and recovery firmware (~3MB) on flash. The rest of flash was used for persistent storage, bootloaders, and calibration data. This is very common for older routers and APs which is the whole reason that OpenWRT exists.

[cyberax]

Well, OpenWRT doesn't even officially support devices with less than 16Mb of flash anymore: https://openwrt.org/toh/views/toh_available_16128

> The rest of flash was used for persistent storage, bootloaders, and calibration data.

So you couldn't spare around 1Mb of compressed flash or 2Mb of uncompressed flash for systemd?

> This is very common for older routers and APs which is the whole reason that OpenWRT exists.

That hasn't been the case in quite some while.

And it won't matter anymore, there is no price difference between 32Mb and 64Mb NOR or NAND flash. It's literally the same cost.

[jalgos_eminator]

> So you couldn't spare around 1Mb of compressed flash or 2Mb of uncompressed flash for systemd?

Absolutely not.

> That hasn't been the case in quite some while

These routers and APs still exist and are in use. Yes, they are 10+ years old, but they're still out there. One of the main goals of OpenWRT is to support legacy networking hardware that vendors abandoned.

[cyberax]

> Absolutely not.

So basically, you're dealing with devices that use obsolete hardware and are designed to be extra-brittle (no safety margin), with a built-in planned obsolescence (what if the new update requires just a bit more space for "calibration data"?). Got it.

sysvinit indeed fits perfectly. Make the system extra unreliable, to provide a stimulus to buy a newer version.

> One of the main goals of OpenWRT is to support legacy networking hardware that vendors abandoned.

And OpenWRT abandoned this goal. OpenWRT also can do nothing about firmware vulnerabilities in the old WiFi chipsets.

Moreover, 10 years ago, systems with 32Mb were already common.

[jalgos_eminator]

OpenWRT doesn't use sysv init, it has something called procd (~120KB compressed). Its very reliable, and they have a large install base on mission critical devices.

> And OpenWRT abandoned this goal.

They have not. Individual devices get too old to be supported, but there are plenty of 16 MB devices they still support. Its true that basically every device now has 32MB or more of flash, but there are still plenty out there that don't.

> with a built-in planned obsolescence (what if the new update requires just a bit more space for "calibration data"?). Got it.

The calibration data is from the factory to tune the wifi radios, it doesn't change since its specific to that individual device. I really hate to reply like this on HN, but you don't seem to know what you're talking about. The kinds of constraints you deal with in embedded networking are different than that in general computing. There's a reason systemd wasn't used, and there's a reason OpenWRT devs went through the trouble of developing their own init system. Just because you can't fathom those reasons doesn't mean they don't exist.

[cyberax]

> OpenWRT doesn't use sysv init, it has something called procd (~120KB compressed). Its very reliable, and they have a large install base on mission critical devices.

procd is only slightly better than sysvinit, it has the same ideas, and only adds simple and incorrectly implemented event triggers. And yes, I spent days debugging issues that it caused.

E.g. a USB drive for the logs becomes slow and changes the startup order, so now openvpn starts before the interface acquires the IPv6 address. Boom, broken IPv6 routing.

> They have not. Individual devices get too old to be supported, but there are plenty of 16 MB devices they still support. Its true that basically every device now has 32MB or more of flash, but there are still plenty out there that don't.

And systemd can live just fine at 16MB. I ran it on RouterBoards with 32MB (the smallest ones available) in 2014. It has grown a bit since then, but it can be slimmed down (remove compressors, auditing, SELinux/AppArmor, etc.).

> The calibration data is from the factory to tune the wifi radios, it doesn't change since its specific to that individual device. I really hate to reply like this on HN, but you don't seem to know what you're talking about.

The entire firmware for WiFi chips that were available during 16MB era is around 500KB-1MB. So it must be some other mysterious "calibration" data.

So you're thinking about more and more corner cases, that require the stars to be just right for the size of systemd to matter.

[jalgos_eminator]

> So you're thinking about more and more corner cases, that require the stars to be just right for the size of systemd to matter.

These weren't corner cases, they were everyday reality. We had to intentionally slim down the firmware size to get it to fit comfortably since we added quite a bit of application code. Like I said before, we got a recovery firmware down to ~3MB, and the normal firmware (without our application) was ~8MB. Every megabyte counts at that point, so having a 1MB init system would be a non-starter. We were buying commodity hardware, so we did lots of shopping and there were still plenty of 16MB APs on the market 10 years ago.

You're right its not a problem if you buy new hardware, but OpenWRT is used to support older devices with limited hardware specs. Its one of the reasons people install it, to give new life to old hardware (rather than being forced to buy a new device).

By the way, I use and like systemd on full size computers. I actually know of a product that runs a full rpm based distro (with systemd) on an embedded device and it works great. But systemd isn't one size fits all.