[Solved] Fastboot oem unlock problem, installing /e/ with Linux, Fedora

On my pc screen it shows:
adb devices

  • daemon not running; starting now at tcp:5037
  • daemon started successfully
    List of devices attached
    A209xxxxxxxx device

So I do:
fastboot oem unlock 6bxxxxxx

and I get on the pc screen:
< waiting for any device >

and my phone is showing the following picture
fastboot

Can anybody tell me what I have to do get the command ‘fastboot oem unlock 6bxxxxxx’ work?