Cannot connect to the Docker daemon. Is the docker daemon running on this host?

Problem:
Cannot connect to the Docker daemon. Is the docker daemon running on this host?

Solution:
docker-machine restart 

then

docker-machine env

eval $(docker-machine env)

ref:
https://github.com/docker/toolbox/issues/296



Following Problems:
1. Too many retries waiting for SSH to be available. Last error: Maximum number of retries (60) exceeded

docker-machine restart

Restarting "default"...

Waiting for SSH to be available...

Too many retries waiting for SSH to be available.  Last error: Maximum number of retries (60) exceeded

2. Error checking TLS connection: Host is not running

docker-machine env

Error checking TLS connection: Host is not running

Solution:

docker-machine start default

docker-machine env

eval $(docker-machine env)

then (to check)

docker image list

Ref:
https://stackoverflow.com/questions/36193300/mac-os-x-sudo-docker-cannot-connect-to-the-docker-daemon-is-the-docker-daemon-r