Got permission denied while trying to connect to the Docker daemon socket at unix

拉取Dockerimages时错误信息如下：

[master@localhost ~]$ docker pull redis
Using default tag: latest
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.39/images/create?fromImage=redis&tag=latest: dial unix /var/run/docker.sock: connect: permission denied

看样子是权限出问题了，将当前用户添加到docker属组中，然后退出重新登陆

usermod -a -G docker master