[FAQF] KC11: Kernel compiling for the beginner.

smouge · Posted: Mon Jun 09, 2003 4:25 pm Post subject:

Nice tips,

I would add to these tips that it is very handy when you have a working kernel, to save the new kernels you make with a different name and to adapt lilo in such a way can boot from both kernels.

For example, my lilo looks like this:

wilburpan · l33t Joined: 21 Jan 2003 Posts: 977

Thanks for the suggestion. I incorporated it into my FAQ.

Stieltje · Posted: Thu Jun 19, 2003 6:42 pm Post subject:

I have 2 kernels now, gentoo-sources and ck-sources, took me a little while to figure out how to get my modules working in the later emerged kernel, ie ck-sources. (setting the symlink linux to my ck-sources directory) . happily I rebooted to see if my gentoo-kernel was still working properly, but no, it could not load any modules at all, the same problem as I had with ck-sources in the beginning......

I want my modules to work using any of my installed kernels, internet has been proven useful in the emerge process....

so, any ideas, did you run into this problem first time you used multiple kernels?

maybe I am missing out on something obvious.

I feel I am a little unclear here, but I really do not know what to state further....

thanks in advance
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smouge · Posted: Thu Jun 19, 2003 8:36 pm Post subject:

Normally you should find your compiled modules in a directory

/lib/modules/2.4.20/kernel
for kernel 2.4.20

or

/lib/modules/2.4.19/kernel
for kernel 2.4.19 etc.

Therefore look if you can find compiled modules in
above directory.

Stieltje · Posted: Thu Jun 19, 2003 9:55 pm Post subject:

nope, no drivers there, or any other place on my hdd except in my /lib/modules/2.4.20-ck6/kernel/drivers folder.

I tried to use copy my drivers into my /lib/modules/2.4.20-gentoo-r2/kernel/drivers folder and modprobe, does not work at all. all I get is the unresolved symbols error.

any other idea?

I have used multiple kernels before, but just the same kernel but with a different release #
but I cannot see why I cannot have a ck-kernel, a gentoo-kernel and a gaming-kernel with working modules installed on my system.....

well, I'll do it all over again :/ see if i stumble over something obvious.

/cheers
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Stieltje · Posted: Thu Jun 19, 2003 11:10 pm Post subject:

ok, I got the solution now.

when I run emerge, it erases the drivers in the other /lib/modules/ folders except for the one for the kernel in use..

the in my eyes uggly solution is to copy the folders with the old drivers, emerge whatever drivers, then copy the old drivers back again, ie saving them from deletion....

that whole system with the symlink thing should be disable-able, maybe it is...

but who many ppl use more than one kernel?

thanks anyway.

/cheers
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lurid · Guru Joined: 12 Mar 2003 Posts: 595 Location: Florida

Although it doesn't work with everything (ie. sometimes modules are required such as lm_sensors or certain video drivers) I generally suggest compiling everything you can into the kernel. Once upon a time when computers didn't have gigs of RAM, small kernels were good to have. Also once apon a time we used these silly things called floppy disks. As neither of these are required anymore (assuming you have at least 128mb ram and can boot from a CD) having mini kernels really servers no purpose.

I like to think of it this way. Lets say there is some catastrophic damage done to your root partition. If everything your kernel needs to boot and possibly repair your data are modules, and thus destroyed with all the other data, how do you boot? By having your kernel completly (as much as possible) self contained and sitting on a seperate unmounted partition (as per Gentoo install instructions) you are pretty much safe in that once you have a working kernel, you'll always have a working kernel.

Stieltje · Posted: Thu Jun 19, 2003 11:37 pm Post subject:

I only use a few modules, for my sound (alsa) and my internet (nvnet, did not see any support in the kernel last time I looked) and for nvidia drivers, ie things i cannot compile into my kernel.

I can boot and have my system running, but without sound and without internet.
I do not argue that a system becomes less waterproof using modules, but I would really like to be able to emerge and compile as many kernels as I want without the extra trouble of copying around my module-drivers. Ok it takes me 20 more seconds, but anyway!

I hope that I help someone to a solution a little faster by spamming this thread

/cheers
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smouge · Posted: Fri Jun 20, 2003 5:58 am Post subject:

It should be no problem running different kernels on one system. I do that as well, 2.4.19, gentoo-sources and openmosix.

I did not know that an emerge will delete the modules of the other kernels, seems weird.

It doesn't look right to copy the modules from one kernel directory to another kernel directory. Better try to have the kernel compilation make the modules. are you sure you used the make modules etc stuff when compiling the kernel?

Anyhow, I always use above mentioned script which you can adapt for other kernels. It is an easy way to change to another kernel and have all the modules compiled, including the NVidia driver and to update lilo (if you use the lilo boot manager).

The only thing I have to compile manuallly when using another kernel is for example the driver fo my pcmcia wifi card. Maybe there are some other modules on your system as well that you have to recompile as well.

using kernel modules yes or no should make no difference in letting your system run. In the beginning I always compiled everything in the kernel, now I use modules as well. Sometimes I need to be able to load or unload a module.

OhSh33t · Posted: Tue Jan 20, 2004 4:17 am Post subject:

why are the initial "kernel conifg suggestions" within this FAQ almost the exact oppisite or whats posted here:

https://forums.gentoo.org/viewtopic.php?t=124530&highlight=

Just seemed strange that when researching on the Gentoo site that I would run into completetly oppisite suggested ways of compiling the Kernel. Not sure what is the right way to proceed now.

Thanks for any suggested clarification.

I'm running 2.4.20-gentoo-r7....and specifically referencing where this FAQ says:

OhSh33t · Posted: Tue Jan 20, 2004 8:16 am Post subject:

I love it when I read the "README" file that accompanies linux pkgs. But this might help others as well if they stumble into looking at this FAQ and the new Genkernel "genkernel-3.0.1" How-To.

Readme..... located at ... "/usr/share/genkernel"

ScottTFrazer · n00b Joined: 19 Sep 2004 Posts: 5

Thanks in no small part to this thread and FAQ, I've managed to compile my first kernel from scratch (actually, I've done five now, each building on the last and adding or removing some little bit of functionality)

One thing I never saw mentioned explicitly was the possibility of using dmesg's output from the livecd as a way of determining what hardware is inside your computer (assuming you don't just know, of course :-)

)

For me it helped determine the chipset of my IDE controller and soundcard on a machine that I had no clue what was inside. Is there a downside to this? Did I just get lucky?

OhSh33t · Posted: Mon Sep 20, 2004 6:03 pm Post subject:

ScottTFrazer · n00b Joined: 19 Sep 2004 Posts: 5

sweet. That's much nicer :-)

griffinme · n00b Joined: 24 Apr 2005 Posts: 23

Two of the three resource links at the end of the article appear to be dead.

Double Click · Tux's lil' helper Joined: 21 May 2004 Posts: 148

Any suggestion on how to deal with remote (through SSH/Putty) compiles? In other words if the new kernel does not work it will default back to a specified working kernel without requiring a manual/physical reboot or intervention?
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nader emami · Posted: Thu Sep 14, 2006 9:38 pm Post subject: A question!

[quote="smouge"]Nice tips,

I would add to these tips that it is very handy when you have a working kernel, to save the new kernels you make with a different name and to adapt lilo in such a way can boot from both kernels.

For example, my lilo looks like this:

truc · Advocate Joined: 25 Jul 2005 Posts: 3199

golding · Posted: Thu Sep 14, 2006 11:05 pm Post subject:

I would like to pare my kernel and modules down to just those needed for this machine.

How would I go about finding exactly what has been loaded so I can answer [N] to all other options in .config?

Is it just a matter of looking at dmesg and lsmod?
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d2_racing · Posted: Sat Feb 10, 2007 9:02 pm Post subject:

Great post

A newbie will know how to debug his kernel with a backup kernel in case that something goes wrong...kernel panic

wynn · Advocate Joined: 01 Apr 2005 Posts: 2421 Location: UK

d2_racing: Thanks â though most of the credit should go to wilburpan as the ideas come from KC11.

If you can spare the time, please keep an eye on it as it evolves. Your comments and corrections are appreciated.
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rodia · Posted: Thu Mar 08, 2007 11:37 am Post subject:

Hello Wynn

Thanks for the link. This is a very full and good tut.

Although I don't use :

wynn · Advocate Joined: 01 Apr 2005 Posts: 2421 Location: UK

Yes, I'd copied the .config from the previous kernel version and used it as the base of the new one with "make oldconfig" for quite some time but recently this failed to work or work properly. For instance, I upgraded from 2.6.18 to 2.6.19 here â carefully adding the SATA drivers, testing the experimental PATA drivers and going back to "old PATA" when they didn't work â but burning CDs was very slow with the minimum buffer fill going down to 7% when it was a minimum of 77% before.

I eventually found out that the DMA on the CD burner hadn't been enabled.

Based on that, I think reconfiguring the kernel starting from "make defconfig" may well take less time, all in all, than just running "make oldconfig" on the old one.

That's why I've written it as it is but, of course, everybody will have their own opinion â these Forums are proof of that, if any was needed

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d2_racing · Posted: Fri Mar 09, 2007 6:08 pm Post subject:

I use make oldconfig when I change of kernel release only.

Exemple : 2.6.19-Gentoo-r2 --> 2.6.19-Gentoo-r5.

Earthwings · Posted: Fri Mar 30, 2007 12:34 pm Post subject:

Updated the old FAQ and merged the comments to the new one to this thread.
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