I'm new to docker.I can't restart virtual machine in docker.I don't know what 'exit status 255' means, while running docker-machine restart vdocker it shows 
$docker-machine restart vdocker
Restarting "vdocker"...
Starting "vdocker"...
<vdocker> Check network to re-create if needed...
<vdocker> Waiting for an IP...
Too many retries waiting for SSH to be available. Last error:Maximum number of retries <60> exceeded
running docker-machine ls shows 
$docker-machine ls
NAME     ACTIVE  DRIVER      STATE    URL                       SWARM        DOCKER    ERRORS
default    *     virtualbox  Running  tcp://192.168.99.100:2376              v1.11.2
vdocker    -     virtualbox  Running                                         Unknown   Somthing went wrong running an SSH command!
command : ip addr show
err     : exit status 255
output  :  
but default machine is working well.
Please let me know if you need any more info or clarity on the problem.