How to fix Docker: Permission denied

I installed Docker on my Ubuntu machine.

When I run

sudo docker run hello-world

it works.

But if I write the command without sudo

docker run hello-world

it 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 a non-root user, then you need to add your user 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. Log in to the new docker group (to avoid having to log out and log in again; but if not enough, try to reboot):

$ newgrp docker

4. Check if Docker can be run without root:

$ docker run hello-world

Reboot if you still get an error:

$ reboot

---

From the official Docker documentation "Manage Docker as a non-root user":

⚠️ Warning

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