assuming the kvm host is up and running already
requirements
which kvm man kvm mkdir -p /etc/qemu/ vi /etc/qemu/bridge.conf allow guestbr0
disk skeleton
guest=bookworm1
mkdir -p /data/guests/$guest/ cd /data/guests/$guest/
–either– skeleton sparse-file
dd if=/dev/zero of=$guest.ext4 bs=1G count=0 seek=10 mkfs.ext4 $guest.ext4 mkdir lala/ mount -o loop $guest lala/
bootstrap
# use same mirror as from host system
cat /etc/apt/sources.list
mirror=`cat /etc/apt/sources.list | awk '{print $2}'`
apt install lsb-release debootstrap
# use same release as host system
lsb_release -cs
time debootstrap --arch=amd64 `lsb_release -cs 2>/dev/null` lala/ $mirror
post-bootstrap
cat > lala/etc/fstab <<-EOF # override /dev/vda1 / ext4 defaults 0 0 proc /proc proc defaults 0 0 tmpfs /tmp tmpfs rw,nodev,nosuid,noatime,relatime 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 EOF
setup the network
vi lala/etc/network/interfaces
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address x.x.x.x/xx
gateway x.x.x.x
unlock the root account
chroot lala/ passwd root ^D
is host kernel suitable for serial output?
ls -lhF /boot/config* grep CONFIG_VIRTIO_CONSOLE /boot/config-6.1.0-32-cloud-amd64 grep -i virtio /boot/config-6.1.0-32-cloud-amd64
get guest kernel modules ready
mkdir lala/lib/modules/ cp -R /lib/modules/6.1.0-32-cloud-amd64/ lala/lib/modules/
fortunately here we’re using same kernel on both sides – anyhow that would be executed at boot-time
chroot lala/ depmod -a
and you’re good to go
umount -R lala/
rmdir lala/
kvm -nic model=help
screen -S consoles
vdisk=/root/guest1.ext4
vdisk=/root/guest2.ext4
vdisk=/root/guest3.ext4
bridge=guestbr0
# we are lucking we're doing a poc using nested virtualization here...
ls -lhF /boot/vmlinuz*
ls -lhF /boot/initrd*
kernel=/boot/vmlinuz-6.1.0-32-cloud-amd64
initrd=/boot/initrd.img-6.1.0-32-cloud-amd64
# beware the path here needs to be /dev/vda not /dev/vda1
kvm --enable-kvm -m 256 \
-display curses -serial pty \
-drive file=$vdisk,media=disk,if=virtio,format=raw \
-kernel $kernel -initrd $initrd -append "ro root=/dev/vda net.ifnames=0 biosdevname=0 mitigations=off" \
-nic bridge,br=guestbr0,model=virtio-net-pci
# init=/bin/bash
# ,mac=xx:xx:xx:xx:xx:xx
# -overcommit mem-lock=off \
# -display none -nographic -serial pty \
# -device virtio-serial-pci,id=serial0 \