With the following instructions, an OpenBSD virtual machine (guest) could be bootstrapped (unattended, autoinstalled) on an OpenBSD host using vmd(8).

To autoinstall(8) OpenBSD vm unattended, it needs to be netbooted following which the installer picks up an answer file via HTTP where the url is a combination of DHCP option server-name and the answer file name; for example: `http://100.64.1.2/install.conf. further details: https://man.openbsd.org/autoinstall.8. With '-L' option, vmctl(8) configures and runs a simple DHCP server for the vm.

First, the host configurations...

1. Enable vmd(8) with...

	rcctl enable vmd && rcctl start vmd

2. A simple config file for httpd(8)...

	doas sh -c 'cat << EOF > /etc/httpd.conf
	server "default" {
		listen on lo0 port 80
	}
	EOF'

3. Enable httpd(8) with...

	rcctl enable httpd && rcctl start httpd

4. An answer file as install.conf is required in /var/www/htdocs, refer to Examples in autoinstall(8).
5. Configure host's firewall to NAT virtual machine traffic with...

	pass out on egress from 100.64.0.0/10 to any nat-to egress

appended to /etc/pf.conf

6. Enable ip forwarding with...

	sysctl net.inet.ip.forwarding=1

Add it to /etc/sysctl.conf as well.

Create a disk for virtual machine...

	vmctl create -s 4.5G disk.qcow2

Start a virtual machine netbooted with the host's ramdisk kernel..

	vmctl start -Bnet -b/bsd.rd -L -m1G -ddisk.qcow2 "vmm1"

This should autoinstall OpenBSD after initial 5 second timeout at boot and pick options given in install.conf answer file. Append -c option to actually see what's happening on the console.

Once the installation completes, the installer reboots the system.

Boot and login to the new virtual machine and attach a console with...

	vmctl start -L -m1G -ddisk.qcow2 -c "vmm1"

With "Local Interfaces" used with option -L, vmctl(8) creates a tap(4) interface on the host which could be used to derive the DHCP IP allocated to the guest vm using its name. Following shell script outputs the vm's IP given its name. The scheme of IP allocation is documented under "LOCAL INTERFACES" section of vmctl(8).

#! /bin/sh

if [ $# -ne 1 ]; then
	echo "usage: $(basename $0) vm_name" >&2 && exit 1
fi

local _n=0
while ifconfig tap$_n > /dev/null 2>&1; do
	ifconfig tap$_n | grep -q "$1" &&
	ifconfig tap$_n | awk '/inet/ { print $2 }' |
	awk 'BEGIN { FS="." } {printf "%d.%d.%d.%d\n", $1,$2,$3,$4+1}' && exit 0
	_n=$((_n+1))
done

exit 1

Example usage:

ip=$(vm_ip.sh vmm1); scp project.tar.gz puffy@$ip: && ssh puffy@$ip 'tar zxvf project.tar.gz && cd project && make'