Regression in 7.1-rc1 in booting Ubuntu distro kernel

[Steve French]

It still is failing with today's Ubuntu mainline build but I don't
think it is related to the module package not being installed.  I see
dpkg showing e.g. "linux-modules-7.1.0-070100rc2daily20260507-generic"
installed, and I also see
"linux-image-unsigned-7.1.0-070100rc2daily20260507-generic" installed

But I am suspicious that the packages are simply missing the initrd
file.  I don't see any initrd fails for 7.1-rc1 or later:

/boot# ls initrd* -lot | more
lrwxrwxrwx 1 root        47 May  7 17:14 initrd.img ->
initrd.img-7.1.0-070100rc2daily20260507-
generic
lrwxrwxrwx 1 root        28 May  7 17:14 initrd.img.old ->
initrd.img-6.17.0-23-generic
-rw-r--r-- 1 root  87410754 May  6 06:41 initrd.img-6.17.0-23-generic
-rw-r--r-- 1 root  88310841 May  1 08:26 initrd.img-7.0.0-070000rc5-generic
-rw-r--r-- 1 root  88290147 Apr 26 20:15
initrd.img-7.0.0-070000daily20260426-generic
-rw-r--r-- 1 root  88327325 Apr 18 20:10 initrd.img-7.0.0-070000-generic

The most recent initrd I see that works is the one from the day before
7.1-rc1 ("initrd.img-7.0.0-070000daily20260426-generic") but I don't
see any of the 7.1 initrd files which looks like a packaging bug in
the Ubuntu mainline kernel since the corresponding linux-image package
is installed.

When I manually extract all of the files from the image .deb:

    dpkg-deb -x
linux-image-unsigned-7.1.0-070100rc2daily20260507-generic /tmppkg/

I only see /boot/vmlinuz not /boot/initrd so it looks like the package
is missing file(s)

root at smfrench-ThinkPad-P16s-Gen-2:/tmppkg/boot# ls
vmlinuz-7.1.0-070100rc2daily20260507-generic

Any ideas how to get current Ubuntu to boot with recent mainline?

On Wed, May 6, 2026 at 2:57 AM Aaron Ma <aaron.ma at canonical.com> wrote:
>
> Hi Steve,
>
> This error is indicated that rootfs is not loaded, please check if the
> kernel module package is installed and initramfs is made for the new
> kernel.
>
> Regards,
> Aaron
>
> On Wed, May 6, 2026 at 2:16 PM Steve French <smfrench at gmail.com> wrote:
> >
> > I notice failures in booting Ubuntu 25.10 on my Lenovo Thinkpad laptop
> > since 7.1-rc1 kernel.  I have not seen this error before.
> >
> > "KERNEL PANIC! Please reboot your computer.  VFS: Unable to mount root
> > fs on unknown-block(0,0)"
> >
> > which doesn't make any sense because that isn't the root fs.  /etc/fstab shows:
> >
> > /dev/disk/by-uuid/6ca90829-120e-4d09-be02-46422daffdcd / ext4 defaults 0 1
> >
> >
> > The last kernel that booted successfully was the daily build from the
> > day before (4/26/26
> > https://kernel.ubuntu.com/mainline/daily/2026-04-26/).  It also fails
> > on current daily builds and on 7.1-rc2 kernel
> > (https://kernel.ubuntu.com/mainline/v7.1-rc2/) so I have been stuck
> > doing my testing on out of tree builds booting from a few weeks old
> > kernel.
> >
> > Any ideas how to find out what regressed in the mainline kernel in
> > 7.1-rc1 (or in the ubuntu mainline daily build) or how to workaround
> > or debug this?
> > --
> > Thanks,
> >
> > Steve
> >
> > --
> > kernel-team mailing list
> > kernel-team at lists.ubuntu.com
> > https://lists.ubuntu.com/mailman/listinfo/kernel-team



-- 
Thanks,

Steve