Problem with vmlinuz-5.4.60-gentoo-x86_64

davidbryant

I've been running Gentoo pretty happily since the end of June. I upgraded my kernel from 5.4.38 to 5.4.48 about a month ago without any trouble.

Yesterday when I updated my system Portage found a new set of kernel sources (5.4.60). So this morning I followed the procedure outlined in the wiki ("Kernel/Upgrade") to update my configuration file, and then compiled the new kernel, generated a new initramfs with "genkernel", and updated my grub.cfg file. All of that went smoothly.

But now, when I boot the new kernel it dies in about 3 seconds: kernel panic, can't locate root file system. I tried re-generating the initramfs file ... it was a little bit bigger the second time, but boot still fails with the same error.

I went through the "kern.log" file for the latest boot with 5.4.48, and I do see some messages I hadn't noticed before.

Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

The shown message seems to be unrelated to me.

Please always post exact error message genkernel/initramfs is showing you.

In case root cannot be found, please show us used kernel command-line and output of the following command:

davidbryant · Posted: Mon Aug 24, 2020 3:10 pm Post subject:

Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

This error message is coming from kernel, not from genkernel's initramfs.

Do you actually see anything genkernel-related on boot? Like "Genkernel 4.1.0 (<your build date>), Linux 5.4.60-gentoo-x86_64"? At the moment I would assume that for some reason, initramfs isn't used.
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davidbryant · Posted: Mon Aug 24, 2020 6:04 pm Post subject:

Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

You cannot compare dracut and genkernel initramfs by size. They don't share anything. They are completely different initramfs.
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davidbryant · Posted: Tue Aug 25, 2020 12:06 pm Post subject:

Banana · Posted: Tue Aug 25, 2020 12:47 pm Post subject:

Does the UUID of a device change with different kernel options?
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Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

NeddySeagoon · Posted: Tue Aug 25, 2020 2:40 pm Post subject:

davidbryant,

Compare the sha512sum of the two files.
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davidbryant · Posted: Tue Aug 25, 2020 6:23 pm Post subject:

Thanks for the suggestion, Neddy.

davidbryant · Posted: Tue Aug 25, 2020 11:21 pm Post subject:

OK, I got some work done. I did all this at one sitting, Whissie. Here is some terminal output.

Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

I am really not understanding what you are trying to proof. See source code, genkernel's initramfs is created completely differently from dracut's initramfs.
Now that you have dracut installed, do "lsinitrd" on dracut's and genkernel's initramfs. This should be really obvious.

Also, I did a comparison for you, https://dev.gentoo.org/~whissi/initrd_comparison.txt

telis · n00b Joined: 01 May 2019 Posts: 5

Hello.
Sorry to jump in, but I had exactly the same problem.
Although I followed the same procedure as always to manually build the kernel and generate an initramfs with genkernel, I got that kernel panic at bootup.
For some reason sys-kernel/genkernel-4.1.0-r2 generated an xz-compressed initramfs (I verified that all previous initramfs images were gzip-compressed, created with older genkernel versions), which the kernel couldn't handle.
I had to turn on CONFIG_RD_XZ in the kernel configuration to make it work.
It seems to me as a change in the default behavior of genkernel?

Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

Please create an own thread for your problem -- this has nothing to do with the discussed topic.

In genkernel-4.0.10, compression handling was fixed (see https://gitweb.gentoo.org/proj/genkernel.git/commit/?id=944da1fc61bd64a47c2bc6415da5e5d5611b6ff5 / https://gitweb.gentoo.org/proj/genkernel.git/commit/?id=0b5192921d06797c806bf908a0e88c1269f56794 and following commits). This maybe cause switching compression from gzip to xz because

telis · n00b Joined: 01 May 2019 Posts: 5

Thank you for the clarifications Whissi.
I understand that manually building the kernel and then using genkernel just to create an initramfs image may lead to incompatible configurations.
The procedure I've been always using to create a new kernel/initramfs pair just happened to work in the past and stopped working after my latest world update (on which genkernel got updated to 4.1.0-r2 and sys-kernel/gentoo-sources got updated to 5.4.60).
It resulted into a non-booting system, I searched for the symptom and the first hit was this thread -- the problem description in the first post matched my case. The discussion that followed triggered me to look at the type of the generated initramfs images and I was able to figure out what was going on. So I thought to report a solution for the next person that runs into the same problem as me and ends up here.

davidbryant · Posted: Wed Aug 26, 2020 9:13 pm Post subject:

I may have created a monster.

I'm sorry to have stirred up so much controversy. When I went back and reviewed what I had done, I realized that I had made a mistake. I'm sorry, Whissi.

I think the real problem is in the "Handbook". It encourages newbies like me to work on kernel configuration, and also points to genkernel as a handy tool for creating an initramfs file. Maybe it ought to reference "dracut".

Here's a link to the chapter I'm talking about. I would gladly edit it, but it's write-protected. And most of the suggestions I have made on the talk pages have been ignored. So there's not much incentive to try to help improve the handbook.

https://wiki.gentoo.org/wiki/Handbook:AMD64/Installation/Kernel

Anyway, it looks as if the bottom line is that one ought not use genkernel to create an initramfs file unless one has also used genkernel to generate the kernel configuration. I'll test that out later today, and post one final message here to let everybody know how it turned out.
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David Bryant
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NeddySeagoon · Posted: Wed Aug 26, 2020 9:18 pm Post subject:

davidbryant,

davidbryant · Posted: Wed Aug 26, 2020 10:53 pm Post subject:

Thank you for the information, Neddy. I'll give it a try.

I did regenerate the kernel and the initramfs file for 5.4.60 using "genkernel all". It boots up fine. The kernel / initrd combination came out about 20% larger than my custom version (19.9 MiB vs. 16.0 MiB), and it takes about 20% longer to get to my sddm login screen (55 seconds vs. 47 seconds). So genkernel is really a very nice tool that saves a lot of work for people who don't want to spend time configuring a custom kernel.

Thanks for the discussion, y'all. I learned a few things.
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David Bryant
Canyon Lake, Texas

Whissi · Retired Dev Joined: 12 Jan 2011 Posts: 222

@davidbryant:

Don't worry, glad we sorted it. I updated handbook in the meanwhile to display a warning, https://wiki.gentoo.org/wiki/Handbook:Parts/Installation/Kernel#Optional:_Building_an_initramfs
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Whissi

davidbryant · Posted: Mon Aug 31, 2020 7:04 pm Post subject:

@Whissi:

Looks good. Thank you.
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David Bryant
Canyon Lake, Texas