Comment 2 for bug 1648995

FWIW, here's my approach for resizing an existing file-backed device, which isn't too much harder than James's original sequence:

  sudo truncate -s +5G /var/lib/lxd/zfs.img
  sudo zpool set autoexpand=on lxd
  sudo zpool online -e lxd /var/lib/lxd/zfs.img
  sudo zpool set autoexpand=off lxd