Look inside .qcow2 files

alpine.txt

pi@4a:~ $ ./vm-explore.sh nocloud_alpine-3.20.3-aarch64-uefi-cloudinit-r0.qcow2 -M alpine
Mounted /dev/nbd0p2 at /media/root/_
Spawning container alpine on /media/root/_.
Press ^] three times within 1s to kill container.
alpine:~#

openwrt.txt

pi@4a:~ $ ./vm-explore.sh openwrt-23.05.2-armsr-armv8-generic-ext4-combined.qcow2 
Mounted /dev/nbd0p2 at /media/root/rootfs
Spawning container rootfs on /media/root/rootfs.
Press ^] three times within 1s to kill container.
  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 -----------------------------------------------------
 OpenWrt 23.05.2, r23630-842932a63d
 -----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------

vm-explore.sh

#!/usr/bin/env -S sudo bash

img=$1

if [[ "$1" == *.qcow2 ]]; then
    img="$1"
else
    img=/var/lib/libvirt/images/$1.qcow2
fi

if ! test -f "$img"; then
    echo $img does not exist
    exit 1
fi

modprobe nbd
qemu-nbd -c /dev/nbd0 "$img"
sleep 0.5
p=$(lsblk -bJ /dev/nbd0 | jq -r '.blockdevices[].children | max_by(.size).name')
udisksctl mount -b /dev/$p
systemd-nspawn -D $(udisksctl info -b /dev/$p | grep -Po '^ *MountPoints: *\K.*') "${@:2}"
udisksctl unmount -b /dev/$p
qemu-nbd -d /dev/nbd0