FAQ: kernel upgrade (and how to avoid unresolved symbols)

jay · l33t Joined: 08 May 2002 Posts: 980

I am posting this because this question has been asked a few times, so here's the Frequently Given Answer. Please feel free to add more informations, if you have any.

First: Here's a little step-by-step instruction:

1. Backup your old kernel

Code:

# mount /dev/hda1 /boot
# cp /boot/bzImage /boot/bzImage.r1
# nano -w /boot/grub/menu.lst

First you're mounting your boot partition, in our case hda1, then we copy the kernel image into a new location and add a boot option in nano:

Code:

title=Gentoo Linux
root(hd0,0)
kernel /boot/bzImage root=/dev/hda3 hdc=ide-scsi

title=Gentoo Linux (Backup kernel)
root(hd0,0)
kernel /boot/bzImage.r1 root=/dev/hda3

2. Download the kernel you want. Normally this is the latest, so you type:

Code:

emerge gentoo-souces

If you prefer a unpatched kernel, then the vanilla-sources are the right option.

3. Change the Symlink The kernels will be placed into /usr/src and the directory tree of /usr/src/linux still points to your old kernel.

Code:

bash-2.05a# ls -l /usr/src
total 16
lrwxrwxrwx 1 root root 22 May 30 14:50 linux -> linux-2.4.19-gentoo-r1
drwxr-xr-x 14 root root 4096 May 30 14:36 linux-2.4.18
drwxr-xr-x 15 root root 4096 May 30 14:55 linux-2.4.19-gentoo-r5
drwxr-xr-x 15 root root 4096 May 23 17:50 linux-2.4.19-r1
drwxr-xr-x 7 root root 4096 May 24 02:47 pc
bash-2.05a#

In our case we have three kernels, 2.4.18 (the vanilla sources) and 2.4.19-rc1 and rc5. We have to change the symlink to the new rc5 kernel. It should look like this then:

Code:

bash-2.05a# ls -l /usr/src
total 16
lrwxrwxrwx 2 root root 22 May 30 14:50 linux -> linux-2.4.19-gentoo-r5
drwxr-xr-x 14 root root 4096 May 30 14:36 linux-2.4.18
drwxr-xr-x 15 root root 4096 Jun 1 18:34 linux-2.4.19-gentoo-r5

drwxr-xr-x 15 root root 4096 Jun 1 18:41 linux-2.4.19-r1
drwxr-xr-x 7 root root 4096 May 24 02:47 pc
bash-2.05a#

4. Clean the directory then compile the kernel to avoid unresolved symbols later.

Code:

#cd /usr/src/linux
#cp .config ../
#make mrproper
#cp ../.config ./
#make menuconfig
#make dep && make clean bzImage modules modules_install
#copy /usr/src/linux/arch/i386/boot/bzImage /boot

This copies your kernel configuration out of the way, before cleaning up module dependencies. When compiling the kernel I recommend to disable in "Processor Types and Features" the Option "Symmetric Multiprocessor Support" unless you have more than one processor in your system, because this causes problems with nvidia drivers very often.

5. Re-Emerge everything that has added modules to your kernel. This is especially true for the nvidia drivers and alsa sound - if you forget this you'll run again into unresolved symbols.

Code:

#emerge nvidia-kernels
#emerge alsa
#umount /dev/hdb1

Then reboot and test if your new kernel works.

Most common problems:

Q: I have emerged the gentoo-sources and when I try to compile I get this error at the end.

T2 · n00b Joined: 01 Jun 2002 Posts: 67 Location: Slovenia

Instead of just copying bzImage to /boot one can rename it to some more meaningful name like

spendabuck · Apprentice Joined: 28 Apr 2002 Posts: 256

what's the code for the symbolic link to change the kernels?

spendabuck · Apprentice Joined: 28 Apr 2002 Posts: 256

https://forums.gentoo.org/viewtopic.php?t=3913&highlight=alsa
what's the code for the symbolic link to change the kernels?

leej · Apprentice Joined: 18 May 2002 Posts: 280

If your new kernel source is:

/usr/src/linux-2.4.19-gentoo-r5

Then you would do a:

spendabuck · Apprentice Joined: 28 Apr 2002 Posts: 256

yes you did thanks.

fghellar · Posted: Tue Jun 04, 2002 5:13 pm Post subject:

Did you have a reason to post your question twice within 10 minutes?
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jay · l33t Joined: 08 May 2002 Posts: 980

You have to remove first the previous symbolik link. For instance

rew · n00b Joined: 28 Aug 2002 Posts: 47 Location: Oregon

jay wrote,

milothurston · Posted: Thu Aug 29, 2002 4:47 pm Post subject:

jay · l33t Joined: 08 May 2002 Posts: 980

You're both right. I think the problem appears only if you are using the SMP kernel with only one processor. At least it was mentioned several times in this forum and mailing list and it happened to me too. So I thought that it wouldn't work on a dual processor system as well. But I'm happy to hear that this is wrong.
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kybber · Posted: Fri Aug 30, 2002 7:25 am Post subject:

rac · Posted: Fri Aug 30, 2002 7:44 am Post subject:

Also note that as of 1.0.2960-r1, you no longer need to reemerge nvidia-kernel after compiling a new kernel. See this thread for details.
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kybber · Posted: Fri Aug 30, 2002 8:04 am Post subject:

Ah, that's very nice indeed - thanks for the tip :-)

However, this is only valid if you don't do any 'serious' changes to your kernel which require a recompilation of the nvidia-kernel against the other modules/libraries etc., right?

rac · Posted: Fri Aug 30, 2002 8:46 am Post subject:

RayVan · n00b Joined: 12 Aug 2002 Posts: 40 Location: Houston, Tx

The step where you move the /usr/src/linux symlink is incorrect, despite the fact that nearly even distribution gets it wrong. Linus' comments on this point are here.

The brief (and less technical) version is this. The /usr/src/linux symlink is /not/ supposed to point at the current kernel version, and has not been supposed to point there since 1.x versions of the kernel. The /usr/src/linux symlink exists so that gcc can find the kernel headers that glibc was compiled against.

IOW, leave the /usr/src/linux symlink alone unless you recompile glibc against the new kernel version.

rac · Posted: Sat Aug 31, 2002 2:10 am Post subject:

rac · Posted: Wed Sep 18, 2002 8:11 am Post subject:

zatalian's kernel compilation question has been split into its own thread here.
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rac · Posted: Thu Sep 19, 2002 7:27 pm Post subject:

bkv's question about keeping old kernel sources around has gone here. Please don't post support questions to threads in Documentation, Tips, & Tricks.
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iKiddo · Guru Joined: 27 Jun 2002 Posts: 341 Location: Europe?

ilovenina · n00b Joined: 02 Oct 2002 Posts: 4

Hi, I am getting unresolved symbols, but I have not upgraded my kernel. this is a fresh install of 1.4.
see my topic
for more info.

Is there anything I can do? Remove my current kernel sources and emerge again? How would I do this safely? Please help...

nbrown · Posted: Tue Oct 29, 2002 7:00 pm Post subject: Still Getting Unresolved Symbols

This guide says that unresolved symbols are a symptom of forgetting to set the symlink correctly, but mine points to my new sources (vanilla) and somehow I'm getting unresolved symbols in my old sources (gentoo). Any ideas on why this is happening? Thanks

Nate

rac · Posted: Wed Oct 30, 2002 1:45 am Post subject:

Please don't post questions to threads in the Documentation, Tips and Tricks forum. This is not a support forum. Ask your question somewhere else. I would split it out myself, but it lacks enough context to make sense on its own in its current form.
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