Comment 5 for bug 1925822

Reproducer from scratch:

# download current cloud image
curl -L -O https://cloud-images.ubuntu.com/daily/server/hirsute/current/hirsute-server-cloudimg-amd64.img
# nothing fancy, just admin:foobar and root:foobar
curl -L -O https://github.com/cockpit-project/bots/raw/master/machine/cloud-init.iso
# create second disk image for formatting
qemu-img create -f qcow2 disk2.img 100M
# boot it
qemu-system-x86_64 -cpu host -enable-kvm -nographic -m 2048 -drive file=hirsute-server-cloudimg-amd64.img,if=virtio -snapshot -cdrom cloud-init.iso -drive file=disk2.img,if=virtio

Log in on the console (root:foobar), then

# sanity check: should be empty
blkid -p /dev/vdb

busctl call org.freedesktop.UDisks2 /org/freedesktop/UDisks2/block_devices/vdb org.freedesktop.UDisks2.Block Format 'sa{sv}' vfat 0

→ hangs.