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tuclogicguy
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Joined: 17 Dec 2013
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 Posted: Mon May 23, 2022 4:05 pm Post subject: How to get past a kernel panic? |
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I have an Intel DH77KC motherboard with an i5-3450 CPU and 12GB of memory. The board has UEFI.
I have two SATA drives configured as RAID0 in the BIOS (using the Intel Rapid Storage Technology feature, sometimes referred to as "fake raid" in these fora.)
I have Windows, Artix Linux and Rocky Linux installed in separate partitions. I'm not using a boot loader; I just use the UEFI boot loader selection screen to select which OS I want to boot.
I am trying to install Gentoo and have been going through the installation instructions carefully step-by-step. For configuring the kernel I only did the following:
Checked jfs file system, because that is how the root partition is formatted.
Unchecked [ ] EFI mixed-mode support
Checked [*] Built-in kernel command line
Added (root=/dev/md126p8) to the command line
I left all other kernel options at their default setting.
I created a new gentoo subdirectory on the EFI partition and followed the instructions at https://wiki.gentoo.org/wiki/EFI_stub
I copied arch/x86/boot/bzImage to /boot/EFI/gentoo/bzImage-5.15.32-gentoo-r1.efi
I used the efibootmgr command to create a new UEFI boot selection pointing to the Gentoo kernel.
When I try to boot Gentoo I get an immediate kernel panic. The screen goes blank and the keyboard Caps Lock and Scroll Lock lights start flashing. No messages are written to the screen.
How do I go about debugging this? What are the typical causes of an immediate kernel panic like this?
Thanks,
Charles Bailey |
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NeddySeagoon
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Joined: 05 Jul 2003
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Location: 56N 3W
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| Posted: Mon May 23, 2022 4:34 pm Post subject: |
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tuclogicguy,
Intel Rapid Storage Technology 'fake raid' requires an initrd to assemble the raid set before the kernel can see the root filesystem to mount it.
The initrd is a small temporary root filesystem used to do the things required to make the root filesystem visible to the kernel.
Some EFI firmware supports loading the initrd as a separate file, some does not, in which case the initrd needs to be built into the kernel.
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Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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tuclogicguy
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Joined: 17 Dec 2013
Posts: 24
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| Posted: Mon May 23, 2022 6:48 pm Post subject: |
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I would think that I would at least get some messages about "unable to mount root file system" or some such. But, I'm not getting any messages at all from the kernel. Is there a "quiet vs verbose" option somewhere?
Charles Bailey |
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NeddySeagoon
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Location: 56N 3W
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| Posted: Mon May 23, 2022 7:01 pm Post subject: |
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tuclogicguy,
You probably have your console support incorrectly configured.
See Framebuffer.
Check the section on Early framebuffer drivers
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Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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tuclogicguy
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Joined: 17 Dec 2013
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| Posted: Mon May 23, 2022 11:49 pm Post subject: |
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Thanks, Neddy, for the advice about Early framebuffer drivers. I didn't have any framebuffer driver enabled. I checked:
[*] EFI-based Framebuffer Support
and now I'm getting lots of messages from the kernel! It says that the cause of the kernel panic is
"VFS: Unable to mount root fs on unknown-block (0,0)"
Obviously, simply checking multi-disk RAID support in the kernel config was not sufficient.
Artix and Rocky Linux both use mdadm to access the RAID0 array. Now, I need to figure out how to get similar support into Gentoo.
Charles Bailey |
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NeddySeagoon
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Joined: 05 Jul 2003
Posts: 54237
Location: 56N 3W
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| Posted: Tue May 24, 2022 11:15 am Post subject: |
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tuclogicguy,
You need an initrd.
Kernel raid auto assembly is for mdadm version 0.90 raid sets only.
| Code: | | unknown-block (0,0) |
means that the kernel cannot communicate with the device holding the root filesystem.
If everything else was well, the kernel will have listed all the block devices it can see.
The empty list is difficult to spot. It says | Code: | | Unable to find root device in . |
where there should be a list in front of the period.
If the list is empty, your block device drivers are configured as modules.
You have two choices here. Add the modules to an initrd or make them built into the kernel binary.
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Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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tuclogicguy
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Hu
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| Posted: Fri May 27, 2022 3:31 pm Post subject: |
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| What had you done wrong, and what did you need to do to make it work properly? Would you consider this thread solved? |
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tuclogicguy
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Joined: 17 Dec 2013
Posts: 24
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| Posted: Sun May 29, 2022 9:19 pm Post subject: |
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I installed mdadm
| Code: | | root # emerge mdadm |
Made sure RAID gets started on boot:
| Code: | | root # rc-update add mdraid boot |
Added "domdadm" to kernel command line.
Rebuilt kernel
Generated initramfs using dracut.
Copied new kernel and initramfs to EFI partition.
Added "initrd=location of initramfs on EFI partition"
On reboot the RAID0 was recognized the Gentoo booted to a command prompt as expected.
Charles Bailey |
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Installing Gentoo
