Questionable Things found in dmesg

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

Hi everyone! Have successfully managed to install Gentoo and have been working with it for about a couple weeks now. No problems so far, but I decided to see what kind of output I got from dmesg. I found that it was throwing alot of errors and I was wondering if anyone knew what they meant

Ant P. · Watchman Joined: 18 Apr 2009 Posts: 6920

The kernel you're running doesn't match the modules it's loading. Either you forgot to `make install modules_install` somewhere or you need to reboot.

NeddySeagoon · Posted: Sat Oct 14, 2017 9:25 am Post subject:

zamlz,

For the kernel versions, its also possible that your clock has made a backwards step it time which has confused make.

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

NeddySeagoon · Posted: Sun Oct 15, 2017 5:44 pm Post subject:

zamlz,

Make tries to be clever to avoid making output files that cannot have changed.
To do that make compares the timestamp on existing output files with that on the input files.
If the input files are all older, then the output file cannot have changed ... unless your clock stepped backwards ...

To can work around that by removing the output files, so that they cannot be reused.

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

Haha, I didn't realize thats what you meant by timing issues with Makefile, I was interpreting that as maybe some multi-threading issue with the compiler. In any case, I did a full rebuild of the kernel, cleaned it up, made the kernel and the modules, and reinstalled both. My /boot is also mounted on startup so it does contain (what I believe to be) the correct files. Unfortunately, the errors still persist.
_________________
AI/ML/Robotics/Linux - zamlz

NeddySeagoon · Posted: Sun Oct 15, 2017 9:44 pm Post subject:

zamlz,

You must have skipped a step.

What does

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

Here is what I get

NeddySeagoon · Posted: Mon Oct 16, 2017 10:50 pm Post subject:

zamlz,

That's yesterday, so your kernel binary looks good. How have you been installing the kernel modules?

-- edit --

Do you have an initrd containing kernel modules?
That needs to be updated every kernel builhd too.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

NeddySeagoon · Posted: Tue Oct 17, 2017 9:17 am Post subject:

zamlz,

The initrd needs to follow the kernel, if it contains kernel modules.
If you build into the kernel, everything you need to boot, so the initrd only contains userspace tools, then its build once and forget.

My initrd is from 2009. It only has the things needed to start kernel raid (mdadm) and logical volume manager, since I have root on lvm on raid5.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

Ah I see. Thanks for the info. So as long I have modules, every time i compile the kernel, I'll need to remake an initrd. In that case, wouldn't it better if I just built all those modules into the kernel? After reading the kernel modules page, I was a little worried using compiled-into-kernel modules vs loadable kernel modules.
_________________
AI/ML/Robotics/Linux - zamlz

NeddySeagoon · Posted: Tue Oct 17, 2017 3:59 pm Post subject:

zamlz,

Only the kernel modules needed to mount the root filesystem need to be built into the kernel.
Once root is mounted, it can read modules from /lib/modules/ if more are needed.

It follows that if you do that and do not need any userspace tools to mount root, you don't need an initrd.

Binary distros and genkernel users get an initrd as these systems provide a run almost everywhere kernel.

There is a downside to built in. Some drivers, notably USB and Wifi are in two (or more parts).
All the parts need to be in the same place. Either built into the kernel or on the root filesystem.
Trial and error is hard, its a kernel rebuild. Modprobing a kernel module to see what its looking for is much faster.

If you are building a public facing server, it does allow module loading to be tumed off entirely, which is one less attack vector.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

zamlz · n00b Joined: 22 Jul 2017 Posts: 42

I see, thanks for the info, I'll definitely look into it some more! And thank you again very much for the help!

_________________
AI/ML/Robotics/Linux - zamlz