make a debian-based os image and chroot for arm (run in arm64 qemu)

setup.sh

#!/bin/bash -e

apt install -y build-essential debootstrap unzip git

# create image
qemu-img create -f qcow2 -o preallocation=metadata rknullos.qcow2 2G
modprobe nbd max_part=8
qemu-nbd --connect=/dev/nbd0 rknullos.qcow2

# paritition
cat << EOF | sfdisk /dev/nbd0
/dev/nbd0p1 : start=        2048, size=      204800, type=6
/dev/nbd0p2 : start=      206848, size=     3987456, type=83
EOF

# setup filesystem
mkfs -j /dev/nbd0p2
mkfs -t fat /dev/nbd0p1
mkdir root
mount /dev/nbd0p2 root
mkdir -p root/boot
mount /dev/nbd0p1 root/boot
debootstrap bullseye root http://deb.debian.org/debian/


echo "type exit to leave the chroot"
chroot root bash

# cleanup
umount root/boot
umount root
qemu-nbd --disconnect /dev/nbd0