@fabian , Thanks for the nifty pointer.
But there appears to be a size mismatch, created 12G:
# pct config 108
arch: amd64
hostname: hdi.loc
memory: 1024
net0: name=eth0,bridge=vmbr0,gw=192.168.63.1,hwaddr=42:E4:13:94:32:93,ip=192.168.63.108/24,type=veth
onboot: 0
ostype: ubuntu
rootfs...