Quck and dirty qemu linux image from linux

qnd.sh

#!/bin/sh

# initially empty image with 8GiB max size
truncate -s 8GiB sda.img
# make dos (mbr) table with one partition
cfdisk sda.img

# mount image as loopback
DEV=$(sudo losetup --find --show --partscan sda.img)
# make root fs
sudo mkfs.ext4 ${DEV}p1

# mount it
sudo mount ${DEV}p1 /mnt

# bootstrap
sudo debootstrap --include=linux-image-amd64,grub2 --components=main,universe stable /mnt

# install-configure loader
sudo systemd-nspawn -D /mnt --bind=$DEV --bind=${DEV}p1 bash -c 'grub-install
--target=i386-pc $DEV && grub-mkconfig -o /boot/grub/grub.cfg'
# fix root partition
sudo sed s/loop.p1/sda1/g -i /mnt/boot/grub/grub.cfg
# reset root password
sudo sed 's/root:[^:]\+/root:/g' -i /mnt/etc/shadow

# unmount
sudo umount /mnt
sudo losetup -d $DEV