Docker: permission denied while trying to connect to the Docker daemon socket

Docker produces "permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock" when the current user is not in the docker group.

What Causes This Error

The Docker daemon socket ( /var/run/docker.sock) is owned by root and the docker group. Non-root users without docker group membership cannot access the socket.

How to Fix

1. Add the current user to the docker group:

sudo usermod -aG docker $USER

2. Log out and log back in for the group change to take effect. Verify with:

groups
docker ps

The groups command should include docker. The docker ps command should work without sudo.