-# this one doesn't need to be done every time
-s qemu-img create -o preallocation=metadata -f qcow2 \
- /var/lib/libvirt/images/demohost 30G
-s qemu-img create -o preallocation=metadata -f qcow2 \
- /var/lib/libvirt/images/demohostb 30G
+
+for f in /var/lib/libvirt/images/demohost{,b}; do
+ [[ -e $f ]] || s qemu-img create -o preallocation=metadata -f qcow2 $f 30G
+done