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

Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.29/containers/1e0ef7e6cf1a/archive?path=%2Fopt%2Fcaffe: dial unix /var/run/docker.sock: connect: permission denied

docker cp 1e0ef7e6cf1a:/opt/caffe /home/miao

Error reason: no sudo added

Change it to:

sudo docker cp 1e0ef7e6cf1a:/opt/deep_ocr /home/miao