The issue is well documented here
I downgraded to the boot2docker.iso 18.06.1-CE that you can download here
Destroy your VMs, then create them again specifying the path to your downloaded boot2docker iso with " --virtualbox-boot2docker-url
".
For example:
docker-machine create --driver virtualbox --virtualbox-boot2docker-url ~/.docker/machine/cache/boot2dockerv18061CE.iso myvm1
Then start again part 4…