Kevin Cui's Blog

Switch Kernel for Fedora(40)

A few days ago, I upgraded from Fedora 39 to Fedora 40. However, after the upgrade, my VirtualBox could not start properly due to a mismatch between the kernel and kernel-header versions.

By using uname -r and dnf list --installed | grep "kernel-headers", I found out the versions are as follows:

I tried to install the matching version of kernel-headers using sudo dnf install kernel-headers-$(uname -r), but found that there was no corresponding version available.

This can also be confirmed on fedoraproject/rpms/kernel and fedoraproject/rpms/kernel-headers, where the latest version of kernel-headers for Fedora 40 is 6.8.3-300.fc40.

Consequently, I decided to downgrade the kernel version to match the available kernel-headers. After verifying its existence, I attempted to install kernel version 6.8.3-300.fc40 using sudo dnf install kernel-6.8.3-300.fc40.x86_64, but dnf indicated that this version was unavailable.

Ultimately, I found a solution on discussion.fedoraproject, where information from Fedora Updates System For F40 allowed verification of the required kernel version, which could then be installed using koji download-build --arch=x86_64 <package name>. The process is as follows:

mkdir kernel-downloads
cd kernel-downloads
koji download-build --arch=x86_64 kernel-6.8.3-300.fc40
sudo dnf install ./kernel-*

Upon completion, it was necessary to switch to the newly installed kernel version. This could be managed using sudo grubby --info=ALL to view the list of system kernels, noting the desired index and kernel. For example:

Grubby info all

Next, a temporary switch to this kernel was made to ensure everything was working properly:

sudo grub2-reboot "3"

The above command sets the system to boot from kernel at index 3 on the next reboot (effective for one time only).

If everything functioned as expected, this kernel could be set as the default:

sudo grubby --set-default /boot/vmlinuz-6.8.3-300.fc40.x86_64

A final check to confirm the default setting was successful:

sudo grubby --default-kernel

From this point on, our system will use the 6.8.3-300.fc40 version of the kernel by default until a dnf update is performed or another version is manually selected.


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