I'm sick of the automatic rename of /kernel to /kernel.old while doing
development that leads to lots of crashes during boot.

I have made a 'reinstall' target (like in ports, and reinstall.debug)
This is most useful if you want to keep /kernel.old as a known bootable
kernel. If you test a new kernel and have to reboot for a fix, a
'make reinstall' will install the new kernel over the top of the old
non-viable one, leaving the old one untouched. This is mainly meant
for development, not general users.