CentOS 8 or RedHat 8 : docker run give error - docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.40/containers/create: dial unix /var/run/docker.sock: connect: permission denied.

After successful installation when i Try to test docker installation with sample container it give following error

[yogesh@devBase ~]$ systemctl start docker
[yogesh@devBase ~]$ docker run test
docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.40/containers/create: dial unix /var/run/docker.sock: connect: permission denied.
See 'docker run --help'.

Solution
Step 1 : Check docker group

[yogesh@devBase ~]$ cat /etc/group

docker:x:970:

if docker group does not exist create it

Step 2 : Add user to docker group

[yogesh@devBase ~]$ sudo usermod -aG docker ${USER}

Step 3 : Above two step not solved the problem now check /lib/systemd/system/docker.socket file.

[yogesh@devBase ~]$ ls -l /lib/systemd/system/docker.socket 
-rw-r--r--. 1 root root 197 Mar 11 06:56 /lib/systemd/system/docker.socket

if user and group of this file is root then change group to docker.

[yogesh@devBase ~]$ sudo chgrp docker /lib/systemd/system/docker.socket 
[sudo] password for yogesh: 
[yogesh@devBase ~]$ 

Step 4 : Give permission to group
[yogesh@devBase ~]$ sudo chmod g+w /lib/systemd/system/docker.socket
Step 5 : open new terminal and restart docker. now run docker run hello-world its working perfectly.

[yogesh@devBase ~]$ ls -l /lib/systemd/system/docker.socket 
-rw-rw-r--. 1 root docker 197 Mar 11 06:56 /lib/systemd/system/docker.socket