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Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

Docker can't reach its background service (the daemon). Every Docker command — run, build, pull — talks to the daemon through a socket file, and if that file isn't there or the daemon isn't listening, nothing works. Either Docker isn't running or the socket path is wrong.

Common causes

  • Docker Desktop isn't started — open the app and wait for it to be ready
  • The dockerd service isn't running on a Linux server: sudo systemctl status docker
  • The DOCKER_HOST environment variable is set to a wrong address
  • Running inside a CI container without Docker-in-Docker configured

How to fix it

  1. On Mac/Windows: start Docker Desktop from the Applications menu or system tray
  2. On Linux: start the service: sudo systemctl start docker, then enable it to start on boot: sudo systemctl enable docker
  3. Verify the daemon is up: sudo systemctl status docker or docker info
  4. If DOCKER_HOST is set, unset it or correct it: unset DOCKER_HOST

Example

$ docker ps Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

Running docker ps on a Linux machine where the Docker service hasn't been started

Related Docker Errors

Permission denied connecting to Docker socketDocker daemon not running on this hostImage not found or pull access deniedImage manifest not found (tag doesn't exist)Unauthorized — authentication required

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