Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?解决方

致使这种状况的缘由暂时不明，不过通过一翻摸索找到一个解决办法

docker ps
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

解决办法以下：

经过命令查看容器名称

$docker-machine ls
NAME       ACTIVE   DRIVER      STATE   URL   SWARM   DOCKER   ERRORS
default    -        virtualbox  Saved                 Unknown   
defaultd   -        virtualbox  Saved                 Unknown

而后执行以下命令启动容器：

$docker-machine start default
Starting "default"...
(default) Waiting for an IP...
Machine "default" was started.
Waiting for SSH to be available...
Detecting the provisioner...
Started machines may have new IP addresses. You may need to re-run the `docker-machine env` command.

在执行以下命令：

$docker-machine env default
export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://192.168.99.100:2376"
export DOCKER_CERT_PATH="/Users/jack/.docker/machine/machines/default"
export DOCKER_MACHINE_NAME="default"
# Run this command to configure your shell: 
# eval $(docker-machine env default)

最后执行以下命令：

$eval $(docker-machine env default)

查看一下容器的状况：

$docker ps
CONTAINER ID        IMAGE                      COMMAND                  CREATED             STATUS               PORTS                               NAMES
be93b47435fd        mysql/mysql-server:latest  "/entrypoint.sh my..."   2 weeks ago         Up 3 days (healthy)   0.0.0.0:3306->3306/tcp, 33060/tcp   mysql

成功！！