You need to change group to docker for user (non-privileged user) otherwise you get following error:-

[user@debasiseric1 ~]$ docker images
 Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get //%2Fvar%2Frun%2Fdocker.sock/v1.37/images/json: dial unix /var/run/docker.sock: connect: permission denied

Now I will login to root

sudo su -

cd /var/run

[root@debasiseric1 run]# ls -al docker.sock
 srw-rw---- 1 root docker 0 Apr 7 07:33 docker.sock

docker is the group which own docker.sock

[root@debasiseric1 run]# id -a user
 uid=1001(user) gid=1001(user) groups=1001(user),10(wheel)

Now add to the group to docker now

[root@debasiseric1 ~]# usermod -aG docker user

[root@debasiseric1 ~]# id -a user
 uid=1001(user) gid=1001(user) groups=1001(user),10(wheel),988(docker)

Now you will be able to run docker command from user

[user@debasiseric1 ~]$ docker images
 REPOSITORY TAG IMAGE ID CREATED SIZE