This is steps to edit configuration.yaml if dashboard is inaccessible due to configuration.yaml error.

  1. login to get out of hassio cli and into bash
  2. docker ps to get a list of containers
  3. note the first 3 characters  for homeassistant - for raspberry pi, the container is something like homeassistant.raspberrypi
  4. docker exec -it 51a /bin/bash
  5. ls to make sure configuration.yaml is there
  6. vi configuration.yaml to edit the file
  7. edit your mistake
  8. esc + :wq to save and exit
  9. exit then login to get back to hassio CLI
  10. core check to make sure the conf is right this time
  11. core restart