Re: Kernel panic, Unable to mount root fs

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On 3/15/26 1:34 PM, Willem Oldeman ([email protected] via lfs-support Mailing 
List) wrote:
> Dear LFS community,
> 
> I am building an LFS 13.0 system, but I run into an issue booting it. Version 13.0- 
> systemd.
> 
> I followed the steps in
> https://www.linuxfromscratch.org/lfs/view/stable-systemd/index.html <https:// 
> www.linuxfromscratch.org/lfs/view/stable-systemd/index.html>
> but my system doesn't want to boot into LFS yet.
> When booting LFS, I get an error: Kernel Panic "Please reboot your computer. VFS: 
> Unable to mount root fs on unknown-block(0,0)".
> 
> Current setup:
> - Ubuntu 24.04 on an Asus laptop, using an nvme drive. Ubuntu loads fine.
> - For now, I want to keep Ubuntu in place as the "mother", since it works.
> - I do not follow https://www.linuxfromscratch.org/lfs/view/stable-systemd/chapter10/ 
> grub.html <https://www.linuxfromscratch.org/lfs/view/stable-systemd/chapter10/ 
> grub.html>, because I do not want to break the mother.
> - The nvme drive has been repartitioned, nvme0p1 through nvme0p3 are for Ubuntu, new 
> partitions nvme0n1p4 (root) and nvme0n1p5 (home) were added for LFS.
> - I have added the entry /etc/grub.d/42_lfs (on mother system) with contents:
> 
> #!/bin/sh
> exec tail -n +3 $0
> menuentry "Linux From Scratch 13.0 (console safe mode)" {
>      insmod part_gpt
>      insmod ext2
>      set gfxpayload=1024x768x32
>      search --no-floppy --fs-uuid --set=root 85dd9c2b-a614-4f09-xxxx
>      linux /boot/vmlinuz-6.18.10-lfs-13.0-systemd \
>          root=uuid=85dd9c2b-a614-4f09-9069-xxxx \
>          ro \
>          nomodeset \
>          nouveau.modeset=0 \
>          modprobe.blacklist=nouveau,nvidia,nvidia_drm,nvidia_modeset,nvidia_uvm
> }
> 
> Where do I go wrong?
> Any hints are welcome :-)

You cannot use root=uuid without an initrd.  Look at the host /dev/disk/by-partuuid/
to find the partition uuid and use:
   root=PARTUUID=<appropriate partition uuid>

Note that 85dd9c2b-a614-4f09-9069-xxxx  is an invalid uuid anyway.
Also the search line and gfxpayload line are meaningless for LFS.

   -- Bruce



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