Gentoo-sources: How to build your kernel without dying trying

Well, this is one more of those points that I cannot ignore before starting the Gentoo installation guide 🙂 I know that many will already be looking forward to this post, and sorry for making you wait, but I also consider that I do not explain this carefully against my Gentoo user status 😛 Without further ado, let's get started.

What is the kernel?

The kernel is properly the Linux part of any distribution, it is the program that allows us to communicate each piece of hardware on our computer with the programs that we run on it. Its creator, Linus Torvalds, decided to release it under the GPL license and thanks to him, and the GNU project, we can now enjoy so many distributions and varieties to choose from. It is mostly written in C, with a bit of Assembly here and there, and today it is the largest free software project, with thousands of developers working on it, both hobbyists and professionals, and maintains a line constant accelerated growth for several years now. Here is the kernel official page so they can take an in-depth look.

How are you on Gentoo?

Well, as is to be expected in Gentoo, there are many kernel options, I leave here a small list for you to see better what I mean:

• gentoo-sources: Kernel 4.12 with special patches for Gentoo Linux.
• git-sources: Kernel directly downloaded from the Linus Git repository.
• vanilla-sources: Full kernel without any patch.
• xbox-sources: Full kernel for Xbox Linux.
• zen-sources: Zen's living kernel
• ...

For a complete list I leave you the wiki link where you can find all the kernels Gentoo maintains in their repositories. (everything ending with -sources)

I have the code, now what?

Well, unlike all other Linux packages, the kernel DO NOT it is updated, it is installed. This allows us to have multiple kernels in our system at the same time, of course, you can always run only one at a time. In order to compile it, it is necessary to use the tools that we have already discussed in a previous post. But since in Gentoo the community does 80% of your work, let's do it the simplest way 😉

genkernel-next:

Let me introduce you to a tool that is just great 🙂 it's called genkernel-next, you can find it in the Gentoo repositories.

The list of options is even bigger, but here are some of my favorite options. One of the most important steps when installing Gentoo is setting of your kernel, this will allow you to get the most out of your computer and at the same time avoid all that extra weight that many pre-compiled kernels have.

CLI and GUI:

As you might expect, the kernel configuration also has various ways of being made 🙂 choices all over the place, just awesome. Here are some of the photos of what the options look like:

genkernel --xconfig all

genkernel –qconfig all

genkernel --nconfig all

genkernel –menuconfig all (my favorite)

Great, but how do I find things?

A wise question that everyone is surely asking themselves right now. If you don't want to have to search line by line, remember that «/ » Y "?» They are your friends on this mission. But since it is better to see than to read, I show you what I mean by this.

Suppose we need to check our processor, the kernel supports both intel and amd, and ours is intel. If you press / (slash), it will take us to the following menu:

Great, now let's see the magic in action 🙂

Great! Now we have a drop-down list with all the information we may need, the technical name of the module, the path, the type of value, etc. And now the question ... how do I get to the location? Also very simple! if we look at the left part, we have numbers inside parentheses. Press one of them and you will see the magic happen again.

As fast as this! We are already in the location we need. But ... wait, I told you that ? is your friend, do you remember? Well let's see what happens if we press? right now.

A short description of the module, its options and dependencies 🙂 all at your fingertips. Once your search is finished, you can exit. You will notice that the top bar has returned to the Search (intel) line, if you exit again, it will return you to the main menu where you can start a new search.

What to move and what not?

At this point you should already feel totally powerful, because you have achieved something that few humans do in their life, compile a kernel. Congratulations! But now the question arises… what should I modify? That my friend, is something that only you can discover, but of course I can give you a couple of recommendations that help me a lot:

The default works

As with all programs, Linux is configured to work with the default settings. This guarantees that even if you don't want to configure anything, when compiling you will have a working kernel.

If you don't know it, don't move it

This is something that perhaps the most adventurous will overlook. It's great to be able to quickly navigate through the options, but if you're interested in really getting to know how your machine thinks, a read of each option is a great way to get used to the idea. Always remembering what you change and searching or comparing with a browser is highly recommended as well.

The biggest weight is on the drivers

Many drivers are loaded by default, this makes the kernel heavy. For example, only for network cards, there are about 10 official drivers in the kernel, and many distributions compile all 10, or more, but in reality you will only use one on your computer (note that for Wi-Fi there is another separate section). If you want to reduce the weight of your kernel considerably, your first option is there. For this, your best friends will be lspci, lsusb, y Google. With this you can have a fairly clear idea of ​​what your system has and only leave the necessary drivers to make it work. For example I leave my lspci output:

With this I can have quite clear critical information, such as my network controller, the Wi-Fi controller, my SATA hard drive, and many other things that help me reduce the weight of my kernel.

Check well that you are compiling what is necessary with *

Thanks again to our partner njord, an important point that I forgot to mention because of the emotion 🙂

It should also be mentioned that there are features of the kernel that should be included within it (*), and others can be handled as modules (M). I remember my first compiled kernel, wanting to leave my root reiserfs support as a module, when in life was it going to work?!?! xD ...

Certainly, if your kernel needs something to work, it cannot be a module. By default, modules load after the kernel has done all the startup process. If your kernel needs something to start, it better be compiled into instead of as module … Which brings us to the first point again "?"  is our friend 😉

In summary:

Well now that you've dived into the kernel world a bit, I think I've already met another milestone needed to be able to generate a ~ 20-step Gentoo install guide 🙂 but if I find anything else out there I'll try to explain before just let loose in the air.

Greetings and I leave you other of my posts in case you miss them:

Gentoo Linux: The Story of a Journey

Gentoo: Why did I choose to compile my own programs?

Gentoo: Heart of the Beast