The script in this repo bootstraps Debian bullseye from a grml live environment. Design decisions and usage instructions are outlined in the beginning of the script.
img="/var/lib/libvirt/images/ts-linux-testing.qcow2"
qemu-img create -f qcow2 -o size=20G $img # create image
qemu-nbd -c /dev/nbd0 $img # create device from image
qemu-nbd -d /dev/nbd0 # release device
# boot grml and setup network if neccessary
git clone https://git.in-ulm.de/ulpeters/bootstrap.git
cp config.sh.template config.sh
vi config.sh
./bootstrap-bullseye.sh install
# reboot
/installer/bootstrap-bullseye.sh postinstall