website/site/blog/2019-10-24-building-an-openbsd-kernel.md

Building an OpenBSD Kernel

I'm running OpenBSD-current for a while in order to support my port. It's only one port at the moment, but that's a start, right?

Anyway... every once in a while I stumble over a patch on the OpenBSD mailing list I want to try and this requires me to apply the patch and build the Kernel with it. But how?

Well, the documentation is where where you would expect it.

Download the kernel source

# cd /usr
# cvs -qd anoncvs@anoncvs.ca.openbsd.org:/cvs checkout -P src

Update the kernel source (if you downloaded it a while ago)

# cd /usr/src
# cvs -q up -Pd

Configure Kernel

# cd /usr/src/sys/arch/amd64/conf
# cp GENERIC.MP MYKERNEL
# config MYKERNEL

Build and install kernel (amd64)

# cd /sys/arch/amd64/compile/MYKERNEL
# make clean
# make
# make install # the old kernel is /obsd now

That's it. Reboot.

This is ONLY the Kernel. If you need to build the whole system, please consult the OpenBSD documentation. The manpage release(8) is a good start.