How do binary distros do their kernel?

[The_Document]

I have been wondering about how binary distros like ubuntu and fedora do their kernel. Do they really enable ALL options? How do only applicable modules load? Does the software probe hardware EVERYTIME it is booted to find appropriate modules to load?(Seems like it already does even with monolithic kernels) How would I go about making a kernel in the same fashion as say ubuntu does but with gentoo? Is there a guide to this kernel fashion?

Couldn't find any answers on my own so I made this topic. I am accustomed to selecting applicable kernel options as built in, I don't use modules except for audio as I have some issues with it being built in.

[audiodef]

I think you want genkernel. Make sure to ~arch keyword it.
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[The_Document]

[Juippisi]

There's debian-sources available in Funtoo's repository. Just a warning, building it requires over 20 GB space so you can be sure it builds every module ;)

Anyway you can study that ebuild and their kernel eclass to do it on Gentoo as well. It uses genkernel.

[John R. Graham]

[Tony0945]

[The_Document]

[John R. Graham]

You're right; I misspoke. The kernel can be configured for many purposes, and depending on purpose, many options are on or off. A typical distro sets up the kernel for desktop usage; this is what Genkernel does. But essentially all of the device drivers are set to be built as modules so that the built-in hardware detection can load them if the hardware is present.

- John
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[The_Document]

[Tony0945]

[krinn]

they just build the kernel with make allmodconfig mostly and enable some critical ones that "should" appears in most users system and are critical to boot : ie, any generic kernel should have ahci build-in because everyone use such controller, if you want a kernel able to boot most adaptec raid cards, you will buildin aacraid (and this is where ubuntu and friends are bloated, because if user is not using aacraid, it will be load unconditionally as only a module may not be loaded if hardware is not present). For ahci it's like a 99% good bet, and even it might appears little to load aacraid, you have to do that for every controller user "might" have, and the list gets long then, adding little bloat over previous one (which might be lowered thru grub option with some "normal kernel" + "kernel for raid" options and proper initram set).
That's the biggest problem there: what controller you should build-in to get your kernel working fine with most configurations.
You have also usb and at keyboard support, for usb build-in or not, you might bet the computer has some usb ports and it will certainly be use, so build-in usb support allowing to boot an usb keyboard, but at keyboard support is adding bloat for user with usb keyboard...

for the other "non critical" modules to boot, they just let the device manager do the work for them as it will autoload module that are needed for hardware.

for other "software" tools (configs or loop per example), you have to either add them to your init autoload module list, or just use them as build-in (again always loaded even not of any use), but you can leave the task to the user to load them when need.
This gave 3 options: opt-in (user load them), opt-out (you have load them, user have to unload them), or bloat (you don't use them as module but buildin).
I don't know which options they use, i think a mix of opt-out and opt-in, and because some hard dumb, maybe bloat too.

[Naib]

this is Ubuntu's config

https://gist.github.com/eeyrjmr/279a0930253831a34be53e74ae4311cb
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#define HelloWorld int
#define Int main()
#define Return printf
#define Print return
#include <stdio>
HelloWorld Int {
Return("Hello, world!\n");
Print 0;

[NeddySeagoon]

Naib,

Postbin please.
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NeddySeagoon

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[audiodef]

If you do a manual kernel config, this tool is very useful. Use it with lspci -n: https://kmuto.jp/debian/hcl/

If you use genkernel, it pays to RTFM. There are many options, including saving/using custom configs to get the desired outcome.

It looks like with a combination of the tool above, genkernel options, and studying what other distros do, you could come up with a custom genkernel config to reliably maintain and update kernels as desired. If you, please share, others might benefit.
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[Jaglover]

Unfortunately kmuto.jp is not maintained. When I drop in my lspci -n it shows no drivers for my 2+ years old motherboard. Use https://cateee.net/lkddb/ instead.
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[Hu]

[The_Document]

[Tony0945]

[eccerr0r]

Also keep in mind many of the other distros keep even the rootfs disk driver as a module and loads it upon boot from the initramfs - so no unused drivers remain in memory despite a generic kernel being used.
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[The_Document]