On a machine WITH bluetooth hardware, the 'bluetoothctl' command works correctly. For example, the command 'bluetoothctl < /dev/null' terminates correctly. On a machine WITHOUT bluetooth hardware, the 'bluetoothctl' command systematically hangs. Even the command 'bluetoothctl < /dev/null' systematically hangs. I have already reported this issue at https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/1565940