Docker - Cannot connect to the Docker daemon

Start docker, and pull bkimminich/juice-shop. Console says

$ docker pull bkimminich/juice-shopUsing default tag: latestWarning: failed to get default registry endpoint from daemon (Cannot connect to the Docker daemon. Is the docker daemon running on this host?). Using system default: https://index.docker.io/v1/Cannot connect to the Docker daemon. Is the docker daemon running on this host?

If docker restarts, it pops up an error windows. Message as follow:

Failed to retrieve settings values.Cannot open socket /Users/someone/Library/Containers/com.docker.docker/Data/s20

How to solve the problem ?

Please try it in your way, maybe you have some important data here.

$ ls -al ~/Library/Containers/com.docker.dockertotal 0drwxr-xr-x    3 someone  staff   102 Jul 28 09:56 .drwx------  174 someone  staff  5916 Dec 15 01:41 ..drwxr-xr-x   20 someone  staff   680 Dec 27 03:50 Data$ ls -al ~/Library/Containers/com.docker.docker/Datatotal 24srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 *00000002.00000202srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 *00000002.000005f4srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 *00000003.000005f5srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 *00000003.00000948drwxr-xr-x  20 someone  staff  680 Dec 27 03:50 .drwxr-xr-x   3 someone  staff  102 Jul 28 09:56 ..srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 @connectdrwxr-xr-x  12 someone  staff  408 Dec 25 22:48 com.docker.driver.amd64-linuxdrwxr-xr-x   3 someone  staff  102 Jul 28 09:57 databaselrwxr-xr-x   1 someone  staff   18 Dec 25 22:48 guest.000005f5 -> *00000003.000005f5lrwxr-xr-x   1 someone  staff   18 Dec 25 22:48 guest.00000948 -> *00000003.00000948srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 s30srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 s31srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 s40srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 s50srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 s51srwxr-xr-x   1 someone  staff    0 Dec 25 22:48 s60-rw-r--r--   1 someone  staff    0 Jul 28 09:57 task.lockdrwxr-xr-x   3 someone  staff  102 Dec 25 22:48 tasks-rw-r--r--   1 someone  staff   37 Dec 25 22:53 user.id$ rm -rf ~/Library/Containers/com.docker.docker/Data

References

1. https://forums.docker.com/t/docker-for-mac-cannot-start/17045/6
2. http://stackoverflow.com/questions/21871479/docker-cant-connect-to-docker-daemon