[gentoo-user] multiple kernel configs

[gentoo-user] multiple kernel configs

[John Dangler]

I changed some options to the menuconfig (trying to get that splash to
work), and saved the changes to an alternate config file.
I'd like to make a kernel with _that_ config file and keep it separate from
my default 2.6-r12 kernel, since, when the splash causes the panic, I have
some way to get back in.

How do I compile a new kernel that I can add to the grub.conf with the
alternate config ?

Thanks for the input

John D



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Re: [gentoo-user] multiple kernel configs

[Marco Matthies]

John Dangler wrote:
> I changed some options to the menuconfig (trying to get that splash to
> work), and saved the changes to an alternate config file.
> I'd like to make a kernel with _that_ config file and keep it separate from
> my default 2.6-r12 kernel, since, when the splash causes the panic, I have
> some way to get back in.
> 
> How do I compile a new kernel that I can add to the grub.conf with the
> alternate config ?

The kernel config file used for compiling the kernel is called .config
So, to compile a kernel with that config file, just replace the .config 
with your alternate file, saving the old .config of course if you want 
to keep it:
mv .config my-old-config
mv my-new-config .config
(do this in the kernel source dir)
  You might have to call 'make clean' before you compile your new 
kernel, i'm not 100% sure on that -- it won't harm though.
You can add as many kernels to your grub config as you like -- you might 
want to check with the install guide how to do that exactly:
http://www.gentoo.org/doc/en/handbook/2005.1/handbook-x86.xml?part=1&chap=10

Basically, your second kernel gets the same kind of entry just as your 
first, but you will want to change the title and of course the kernel 
(the root line should be the same as in the first block). Move your 
kernel under the name you specified to the same location where your 
other kernel is, using the name you specified in the config. (you will 
probably have to mount your /boot partition to do all this naturally)

I.e. add an extra block something like this to your grub.conf:

title=Gentoo Linux 2.6.11-r11
root (hd0,0)
kernel /kernel-2.6.11-gentoo-r11

Marco
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RE: [gentoo-user] multiple kernel configs

[John Dangler]

Does the moving of the config files have any effect on the already compiled
kernel? (I was under the impression that a .config _went with_ a specific
build) or is that a throwback to too much time in a m$ environment?

John D

-----Original Message-----
From: Marco Matthies [mailto:marco-ml@gmx.net] 
Sent: Friday, August 19, 2005 9:46 PM
To: gentoo-user@lists.gentoo.org
Subject: Re: [gentoo-user] multiple kernel configs

John Dangler wrote:
> I changed some options to the menuconfig (trying to get that splash to
> work), and saved the changes to an alternate config file.
> I'd like to make a kernel with _that_ config file and keep it separate
from
> my default 2.6-r12 kernel, since, when the splash causes the panic, I have
> some way to get back in.
> 
> How do I compile a new kernel that I can add to the grub.conf with the
> alternate config ?

The kernel config file used for compiling the kernel is called .config
So, to compile a kernel with that config file, just replace the .config 
with your alternate file, saving the old .config of course if you want 
to keep it:
mv .config my-old-config
mv my-new-config .config
(do this in the kernel source dir)
  You might have to call 'make clean' before you compile your new 
kernel, i'm not 100% sure on that -- it won't harm though.
You can add as many kernels to your grub config as you like -- you might 
want to check with the install guide how to do that exactly:
http://www.gentoo.org/doc/en/handbook/2005.1/handbook-x86.xml?part=1&chap=10

Basically, your second kernel gets the same kind of entry just as your 
first, but you will want to change the title and of course the kernel 
(the root line should be the same as in the first block). Move your 
kernel under the name you specified to the same location where your 
other kernel is, using the name you specified in the config. (you will 
probably have to mount your /boot partition to do all this naturally)

I.e. add an extra block something like this to your grub.conf:

title=Gentoo Linux 2.6.11-r11
root (hd0,0)
kernel /kernel-2.6.11-gentoo-r11

Marco
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Re: [gentoo-user] multiple kernel configs

[Marco Matthies]

John Dangler wrote:
> Does the moving of the config files have any effect on the already compiled
> kernel? (I was under the impression that a .config _went with_ a specific
> build) or is that a throwback to too much time in a m$ environment?

the .config file determines how and especially which parts of the kernel 
are built by the kernel build environment -- the .config has no effect 
after the kernel has been built.
a windows kernel will probably be built similarly, though who knows what 
happens in the kernel caverns of redmond... :)

Marco
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Re: [gentoo-user] multiple kernel configs

[Etaoin Shrdlu]

John Dangler wrote:

> I changed some options to the menuconfig (trying to get that splash
> to work), and saved the changes to an alternate config file.
> I'd like to make a kernel with _that_ config file and keep it
> separate from my default 2.6-r12 kernel, since, when the splash
> causes the panic, I have some way to get back in.
>
> How do I compile a new kernel that I can add to the grub.conf with
> the alternate config ?

Just copy it in /boot with a different name, and add an entry in 
grub.conf for that. For future reference, I also always save the 
config files in a dedicated directory.

Example (with a lot of fantasy, I name kernels using their version 
number, but that's of course just personal preference):

# ls /boot
2.6.11.11  Sytem.map-2.6.11.11

This is where I save the configs (again, you might want to do it 
differently):

# ls /root/conf
2.6.11.11.conf

Relevant section of grub.conf:

title 2.6.11.11
        root (hd-whatever,n)
        kernel (hd-whatever,m)/2.6.11.11 root=/dev/hda3

Now suppose I want to do some tests with new features, so this is what 
I do:

# cd /usr/src/linux
# make mrproper    (I think this is not strictly required, I usually 
do it)
# make menuconfig

(load the config file from /root/conf/2.6.11.11.conf, adjust what you 
want to change, and save the config back to /root/conf but with a 
different name to preserve the old one, 
e.g. /root/conf/2.6.11.11-newfeatures.conf

Optionally you may also want to append an EXTRAVERSION to the kernel 
version - something that will show up when you do "uname -a" - IIRC 
there's now a dedicated menuconfig entry to do this, otherwise you 
can just edit the Makefile after menuconfig)

# make && make modules_install
# cp arch/i386/boot/bzImage /boot/2.6.11.11-newfeatures

(Optional, but I usually do this, expecially if I set the 
extraversion)
# cp System.map /boot/System.map-2.6.11.11-newfeatures

Edit grub.conf, and add a line like this after the existing one:

title 2.6.11.11-newfeatures
        root (hd-whatever,n)
        kernel (hd-whatever,m)/2.6.11.11-newfeatures root=/dev/hda3

Reboot and you'll see both entries in the grub boot menu.

Hope this helps.
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