Docker: Permission Denied on /var/run/docker.sock

You install Docker, run docker ps, and get slapped with:

permission denied while trying to connect to the Docker daemon socket at
unix:///var/run/docker.sock

This isn't a broken install. Docker talks to its daemon over a Unix socket, /var/run/docker.sock, and that socket is owned by root and the docker group. Your regular user is in neither — so the kernel refuses the connection.

Why sudo "fixes" it (and why that's a trap)

sudo docker ps works because root can open the socket. But typing sudo before every command is a symptom, not a cure — and it means files created by containers end up owned by root. The real fix is to grant your user access properly.

Step 1: Add your user to the docker group

sudo usermod -aG docker $USER    # -a appends, -G names the group

This makes your user a member of the docker group, which owns the socket.

Step 2: Start a fresh session

Group membership is only read at login, so your current shell still doesn't know about it. Log out and back in, or force a new session:

newgrp docker      # or just close the terminal and reopen it
docker ps          # should work now, no sudo

If docker ps still fails right after usermod, you almost certainly skipped the re-login step — the old session is running with your old group list.

If it's still denied

Check the daemon is actually running and the socket exists:

systemctl status docker          # is the daemon up?
ls -l /var/run/docker.sock       # srw-rw---- root docker

The socket should be group-owned by docker. If the daemon is stopped, sudo systemctl start docker first.

The security footnote

Being in the docker group is effectively root-equivalent — a container can mount the host filesystem. That's fine on your own machine; on a shared server, treat docker group membership as handing out admin.

The checklist

1. sudo usermod -aG docker $USER
2. Log out and back in (or newgrp docker).
3. docker ps with no sudo.
4. Still stuck? Check systemctl status docker and the socket's group.