Re: kernel panic booting from USB flash drive

Am 14.10.24 um 06:22 schrieb Michael Peters ([email protected]
via lfs-support Mailing List):
> Build Host: x86_64 LFS 11.3 SystemV running kernel 6.6.56
> 
> I'm building LFS 12.2 SystemD (also kernel 6.6.56, I prefer LTS kernels) to
> a
> USB flash drive (using shell scripts) with the intent of then booting from
> the
> USB flash drive to re-run my scripts to build it to a partition on the hd.
> 
> Everything is working well *except* the boot.
> 
> The flash drive is a single ext4 partition created by using fdisk (LFS
> 11.3) to
> delete what the manufacturer put on it, create a single primary partition of
> type Linux, and marking the partition bootable in fdisk.
> 
> I then format the single partition with mkfs.ext4 (I *probably* should have
> used
> ext2 but that's not the issue).
> 
> LFS builds on it (albeit slowly), kernel installs, grub-install on /dev/sdi
> from
> within the chroot after building kernel reports no problems.
> 
> This is the grub.cfg I initially tried:
> 
>     # Begin /boot/grub/grub.cfg
>     set default=0
>     set timeout=5
> 
>     insmod part_gpt
>     insmod ext2
>     search --set=root --fs-uuid add2119a-1a46-4c72-b212-863ee869ebd1
> 
>     #USB Flash Grub
> 
>     menuentry "USB Flash GNU/Linux, Linux 6.6.56-lfs-12.2-systemd" {
>       linux /boot/vmlinuz-6.6.56-lfs-12.2-systemd root=PARTUUID=8d5d11ba-01
> ro
>     }
> 
> The UUID and PARTUUID are from the `blkid` command and are correct, and LFS
> 11.3
> booting from a hard drive is just fine with me using them so that changes
> in the
> device name don't cause issues.
> 
> When booting off the flash drive, the grub menu appears and it actually
> starts
> to boot but I get
> 
>     [    0.605403]  msdos
>     [    0.605474]  iso9660
>     [    0.605545]
>     [    0.605685] Kernel panic - not syncing: VFS: Unable to mount root fs
> on unkno
>     wn-block(0,0)
>     [    0.605770] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 6.6.56 #1
>     [    0.605850] Hardware name: Supermicro X10SLH-F/X10SLM+-F/X10SLM+-F,
>     BIOS 3.3 03/27/2020
>     [    0.605934] Call Trace:
>     [    0.606011]  <TASK>
>     [    0.606077]  dump_stack_lvl+0x38/0x50
>     [    0.606157]  panic+0x170/0x320
>     [    0.606238]  mount_root_generic+0x24b/0x300
>     [    0.606317]  ? rest_init+0xc0/0xc0
>     [    0.606394]  prepare_namespace+0x5e/0x270
>     [    0.606471]  kernel_init+0x11/0x1a0
>     [    0.606567]  ret_from_fork+0x28/0x40
>     [    0.606646]  ? rest_init+0xc0/0xc0
>     [    0.606722]  ret_from_fork_asm+0x11/0x20
>     [    0.606799]  </TASK>
>     [    0.606897] Kernel Offset: 0x16c00000 from 0xffffffff81000000
> (relocation ran
>     ge: 0xffffffff80000000-0xffffffffbfffffff)
>     [    0.606987] ---[ end Kernel panic - not syncing: VFS: Unable to
> mount root fs
>      on unknown- block(0,0) ]---
> 
> (above manually transcribed from photo)
> 
> It's definitely the Linux kernel and not a bios related kernel as the kernel
> version is clearly visible.
> 
> I tried changing
> 
>     search --set=root --fs-uuid add2119a-1a46-4c72-b212-863ee869ebd1
> 
> to
> 
>     set root=(hd4,1)
> 
> and I tried changing
> 
>     root=PARTUUID=8d5d11ba-01
> 
> to
> 
>     /dev/sdi1
> 
> but when I do that, grub can't even find the kernel. Clearly one or both of
> those relative device references is wrong when I try it, I suspect the
> `set root=(hd4,1)` as I have four physical SATA drives which I think should
> correspond to (hd0--hd3) but with bios boot order set to USB first, who
> knows?
> 
> But anyway I think the `UUID` and `PARTUUID` should work and when used,
> clearly
> the kernel loads enough to panic.
> 
> Same kernel config used as what works with LFS 11.3 but I wonder if maybe
> there
> are some kernel options I need (or need as built-in instead of modular) to
> boot
> a kernel off of USB? Anyone know?
Your original grub.cfg seems OK to me.  The problem is that the kernel
can't load the root file-system.  I'd check the partition-table-type of
the stick with
lsblk -lo NAME,PTTYPE

and then check whether you have built the kernel with support for that type:
grep -Ei "msdos_partition|efi_partition" .config

Perhaps one of the following is missing:
CONFIG_MSDOS_PARTITION=y
CONFIG_EFI_PARTITION=y

HTH

Rainer

> 
> Would it be better to make an initramfs that lets kernel modules load
> before the
> filesystem is mounted and does anyone have a clear reference to that
> process?
> 
> Thank you for your time.
> 
>

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