Upgrading Ubuntu OS causes symbol mismatch on older kernels

[norman-a]

On a 22.04 Ubuntu I have my dkms module installed on a 6.8.0-87-generic kernel.

When I upgrade Ubuntu from 22.04 to 24.04, DKMS correctly installs the module on the new kernel 6.8.0-88-generic and the module runs fine on it.

However, booting into the older kernel once the upgrade is finished will fail to load the DKMS module, with dmesg printing:

module: disagrees about version of symbol X
module: Unknown symbol X (err -22)

If I reinstall the dkms debian package on the older kernel after the upgrade the issue gets resolved, but I'm curious if there's a way to prevent this.

[scaronni]

Why are you booting the Ubuntu 22.04 kernel on 24.04? If there's something that there's too many copies around, it's kernels in Ubuntu.

[scaronni]

Also, you did not post any output of the state of your system (dkms status, log files, kernel packages installed, etc.) and on top of that the compiler in Ubuntu 24.04 is not the same as in 22.04, so the compiler does not match with the kernel used in the 22.04; so I doubt that will work.

[norman-a]

@scaronni here's dkms status

module/4.9.0.10, 5.15.0-43-generic, x86_64: installed
module/4.9.0.10, 6.8.0-87-generic, x86_64: installed
module/4.9.0.10, 6.8.0-88-generic, x86_64: installed

5.15.0-43 and 6.8.0-87 were installed on 22.04, and while i was on that OS the modules would load fine. As for why booting into the old kernel, I'm just testing my DKMS package to see if it'll work for other people who might want to do that for whatever reason. By compiler do you mean the gcc compiler?

[scaronni]

5.15.0-43 and 6.8.0-87 were installed on 22.04, and while i was on that OS the modules would load fine.

Exactly, the compiler must match. https://github.com/dkms-project/dkms/blob/main/dkms.in#L1445

[norman-a]

is there a way to have dkms rebuild and install the module on all the kernel versions during an OS upgrade with the new compiler? setting autoinstall_all_kernels=yes in /etc/dkms/framework.conf didn't do the trick

[scaronni]

It should already, but the compiler is different for the old kernels and not installed, so as I already said, probably it won't work. You should not mix pre-packaged kernels across distributions.

Also, you did not specify which DKMS version are you using.

[norman-a]

~# dkms --version
dkms-3.0.11