This error is with libguestfs 1.20. Calling guestfs_launch() with tracing on: supermin helper [00065ms] finished creating appliance libguestfs: checksum of existing appliance: 2bd6811426e14b6fb661b4d52cebd6c21a41df1a068e8acf6a7a08e3b3bd4ada libguestfs: trace: get_cachedir libguestfs: trace: get_cachedir = "/var/tmp" libguestfs: [00071ms] begin building supermin appliance libguestfs: trace: get_cachedir libguestfs: trace: get_cachedir = "/var/tmp" libguestfs: [00071ms] run febootstrap-supermin-helper libguestfs: command: run: febootstrap-supermin-helper libguestfs: command: run: \ --verbose libguestfs: command: run: \ --copy-kernel libguestfs: command: run: \ -f ext2 libguestfs: command: run: \ /usr/local/lib/guestfs/supermin.d libguestfs: command: run: \ x86_64 libguestfs: command: run: \ /var/tmp/guestfs.lQs0RL/kernel libguestfs: command: run: \ /var/tmp/guestfs.lQs0RL/initrd libguestfs: command: run: \ /var/tmp/guestfs.lQs0RL/root febootstrap-supermin-helper: unrecognized option '--copy-kernel' febootstrap-supermin-helper: build the supermin appliance on the fly Usage: febootstrap-supermin-helper [-options] inputs [...] host_cpu kernel initrd <snip> Same code works on a different system. Both systems are Ubuntu 12.04. However the system that works is using Linux 3.6.4-pv whereas the system that fails is Linux 3.5.4-pv. Do I need to upgrade the kernel?