How to fix docker: Got permission denied issue

I installed Docker in my machine where I have Ubuntu OS.
When I run:

sudo docker run hello-world

All is ok, but I want to hide the sudo command to make the command shorter.
If I write the command without sudo

docker run hello-world

That displays the following:

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/v1.35/containers/create: dial unix /var/run/docker.sock: connect: permission denied. See 'docker run --help'.

The same happens when I try to run:

docker-compose up

How can I resolve this?

If you want to run docker as non-root user then you need to add it to the docker group.

1. Create the docker group if it does not exist

$ sudo groupadd docker

2. Add your user to the docker group.

$ sudo usermod -aG docker $USER

3. Run the following command or Logout and login again and run (that doesn't work you may need to reboot your machine first)

$ newgrp docker

4. Check if docker can be run without root

$ docker run hello-world

Reboot if still got error

$ reboot

Warning

The docker group grants privileges equivalent to the root user. For details on how this impacts security in your system, see Docker Daemon Attack Surface..

Taken from the docker official documentation: manage-docker-as-a-non-root-user

After an upgrade I got the permission denied. Doing the steps of 'mkb' post install steps don't have change anything because my user was already in the 'docker' group; I retry-it twice any way without success.

After an search hour this following solution finaly worked :

sudo chmod 666 /var/run/docker.sock

Solution came from Olshansk.

Look like the upgrade have recreate the socket without enough permission for the 'docker' group.

Problems

This hard chmod open security hole and after each reboot, this error start again and again and you have to re-execute the above command each time. I want a solution once and for all. For that you have two problems :

• 1) Problem with SystemD : The socket will be create only with owner 'root' and group 'root'.

  You can check this first problem with this command :

  ls -l /lib/systemd/system/docker.socket
  

  If every this is good, you should see 'root/docker' not 'root/root'.

• 2 ) Problem with graphical Login : https://superuser.com/questions/1348196/why-my-linux-account-only-belongs-to-one-group

  You can check this second problem with this command :

  groups
  

  If everything is correct you should see the docker group in the list. If not try the command

  sudo su $USER  -c groups
  

  if you see then the docker group it is because of the bug.

Solutions

If you manage to to get a workaround for the graphical login, this should do the job :

sudo chgrp docker /lib/systemd/system/docker.socket
sudo chmod g+w /lib/systemd/system/docker.socket

But If you can't manage this bug, a not so bad solution could be this :

sudo chgrp $USER /lib/systemd/system/docker.socket
sudo chmod g+w /lib/systemd/system/docker.socket

This work because you are in a graphical environnement and probably the only user on your computer. In both case you need a reboot (or an sudo chmod 666 /var/run/docker.sock)