How should I get kernel headers?

[Luluc]

I need kernel headers for Virtualbox. That is available on Synaptic, but considering I upgraded the kernel from a built-in menu rather than from Synaptic, I wonder if the repository kernel headers will work. I tried and I'm having problems. Not sure if it's because of that.

[fredx181]

@Luluc Can you tell more about what you did ? On Bullseye I assume ?
Anyway, it should work, but the linux-headers version must match exactly with the kernel you are running.