Docker socket permission prevents Traefik from discovering containers

Traefik cannot read /var/run/docker.sock due to insufficient permissions, preventing Docker provider from discovering containers. Occurs when Traefik runs as non-root user and socket permissions don't grant access. Results in no routers being created, provider errors in logs, and complete inability to route traffic to Docker containers.

Check socket permissions from Traefik container with 'docker exec traefik ls -l /var/run/docker.sock'. Verify socket is mounted with 'docker inspect traefik' checking Mounts section. Check Traefik logs for provider connection errors. Solutions: run Traefik with user in docker group, mount socket with appropriate permissions, or adjust socket group permissions on host. Ensure socket mount is read-only (:ro) for security.