If you are encountering the error "Kernel headers not found for target kernel" while installing VirtualBox Guest Additions, the solution to resolve the issue is by installing kernel-devel
package.
Open terminal and run command uname -r
to list current linux kernel version:
uname -r
The output is similar to:
6.2.9-300.fc38.x86_64
Then install the kernel-devel
package which matches the current linux kernel version:
sudo dnf install kernel-devel-6.2.9-300.fc38
When the installation is complete, go to directory where VirtualBox Guest Additions image file is mounted.
cd /run/media/$USER/VBox_GAs_7.0.8/
Then install the VirtualBox Guest Additions again
sudo ./VBoxLinuxAdditions.run
The error should disappear now.
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Then restart your system.
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If the Fedora guest still doesn't fit screen, try to resize the window.
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