Jan Danielsson <jan.m.danielsson@gmail.com> wrote:

>    I've always assumed that /netbsd is loaded entirely into memory at
> boot, and is thereafter just laying there, waiting for the next reboot.
> 
>    But when I boot from a special boot device, and "sysctl init.root" to
> wd0a, and /netbsd is missing from wd0a, I get warnings. It seems to boot
> anyway; but is the presence of /netbsd important on a root partition,
> even if it isn't actually used for boot?

High level answer, with a little hand waving: some programs look at
/netbsd to get the addresses of symbols in memory.  Such programs are
out of fashion (search with your favourite search engine for "kmem
grovellers".

Keeping a copy of /netbsd (which should exactly match the actual boot
kernel!) on your root partition is good practice, and may indeed be
needed for full functionality.

Giles