The basics about kernel compiling?

[Garrosh]

I've been running a linux box with a quad core for nearly a year now. I've managed to make work most of everything I set my mind to except for one very important thing: the four cores. As I gather, I would need to compile my kernel with "the right options" and then I could avoid seeing my computer hang with only 26-27% CPU usage... So I wonder what those right options are, and where do I find them, and what do I need to know to find them. I basically need someone to point me in the right direction so I can avoid destroying my OS, since its a risk to take if I try to compile. I hear a lot about tweaking, but haven't found anything really clear on that topic either.

Thanks in advance.

[UndiFineD]

There is a chance that your kernel along with all your libraries are running in "i686" mode, so when you have build your new kernel your libs would not work (properly)
Do you have a /lib64 ?
maybe you like to have fun with linux and learn a few bits: www.linuxfromscratch.org

[Garrosh]

I am running a 64 bit OS since my chip is native 64 bit. Its AMD, by the way. So I do have a /lib64, and a very smal /lib. What I currently have running is some pretty standard Mandriva setup, I guess. I've started to read that link you gave me, and I am really impressed. It seems that the task of using my four cores is more complex than I expected, but building from scratch would let me do this and streamline my system as well, wich is awesome. Thanks!

It might be important to specify that due to issues with SATA2 and DVDs (i could elaborate) I installed a very basic install from a dual arch CD. It was the only way I could find to install a 64 bit system on my box. I then proceeded to insall everything I need, including KDE 4. I am fairly satisfied with what I've done so far since everything works as I like, but for my 3 other cores. I will probably build from scratch to remove all the spam my explorations may have put on my hard drive, but I would like confirmation that I can't just install something or run a script that would just fix everything :D

[UndiFineD]

well it is good to hear you like it. lfs is a great way to expand your knowledge.
but in your case a different kernel would solve your immediate issue.

in a shell type 'uname -a' to get your current running kernel info

download the following kernel package that is the same as your current kernel:
http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.30.4.tar.bz2
is the current latest 'stable'
you may need a new copy of linux-headers too.

/usr/src/linux is a symlink to your kernel source tree.
if not there? 'ln -s linux-source-2.6.30 linux'
go there and type: 'make mrproper'

copy your current running kernel config file /boot/config* to /usr/src/linux
rename the copied config* file to /usr/src/linux//.config

and follow the guide: README

[Garrosh]

So a kernel update would fix my problem you think? I do have 2.6.29.6 running, and checked my .config file, and its apparently setup to use all four... Oh, wait, I think I get it. What you just gave me are the few simple steps to compile the newest kernel on my system, right? So it doesn't need fancy options and I just have to carry over my .config file?

[UndiFineD]

well, this way you can check if all the kernel settings are right,
if you need changes you can make them,
if you want to upgrade the kernel, be my guest.
maybe there are patches floating around the internet you may need, etc
processor tweaks, ramdisk size, better support for your hardware,
network stack, etc

and the lfs part can be done in a virtual machine like qemu :-)

[Garrosh]

When you say I can check if all the kernel settings are right, do you mean by trial and error? Because there sure are lots of them in the .config file. I have no idea some of them mean, but I guess I could figure it out. The patches you mentionned, are they kernel patches? If so would one be required to get my 4 cores working? I'm asking this because I've never compiled my kernel, see. I've only installed the precompiled versions for AMD x86_64 architectures. I'm starting to get the feeling the precompiled stuff is far from perfect, so LSF would allow me to make it so. However, would it resolve my outstanding issue if I just compile my kernel? From what you tell me, it might. And from what you also told me, compiling the kernel isn't anything really fancy, I just have to make sure I carry over my old .config file, then make changes to it as needed. Did I understand everything? If yes, then this situation is solved!

[UndiFineD]

the guide is in
/usr/src/linux/README
if you taken the steps I showed you before
all you have to type now is
'make menuconfig'

patches can be found on the ftp of kernel.org
but the kernel image by itself is usually good enough
it may be that mandrake / mandriva added a couple of patches of themselves
but even those end up in the kernel eventually
(when those patches are good enough)

[Garrosh]

All right, I did the make menuconfig thing, and there a quite a lot of kernel options to swich through. I don't know if I can sort through all of them, but slowly I'll work my way through them. The LSF site is very helpful to get me the information I need to pick the right options. Thanks a bunch!