Docker daemon unavailable

What this failure means

Docker could not reach the daemon socket or service, so the step failed before it could inspect containers or run a build.

Symptoms

Faultline looks for one or more of these log fragments:

Cannot connect to the Docker daemon
Cannot connect to the docker daemon
Is the docker daemon running?
Docker daemon is not running
failed to connect to the Docker daemon
failed to connect to docker daemon
unable to connect to the Docker daemon
dockerd failed to start

Diagnosis

Docker could not reach the daemon socket or service, so the step failed before it could inspect containers or run a build.

This usually means the daemon is stopped, the socket path is wrong, or the environment does not expose Docker at all.

Fix steps

1. Check whether the Docker daemon is actually running on the host or runner.

2. Verify the expected socket is mounted or the Docker service is available to the job.

3. If you are using Docker-in-Docker, confirm the sidecar or service container started before the job step.

4. Re-run a minimal probe from the same environment:

   docker info
   docker ps
   

Validation

• docker info succeeds from the same job environment.
• Re-run the failing step and confirm the Docker daemon is reachable.

Why it matters

If the daemon is unavailable, every downstream Docker action fails: image pulls, container starts, registry checks, and build steps.

Prevention

• Start the Docker service before the job tries to use it.
• Mount the socket or configure DinD explicitly instead of assuming a host daemon exists.
• Add a lightweight docker info probe at the top of jobs that depend on Docker.

Try it locally

docker info
docker info

How Faultline detects it

Use faultline explain docker-daemon-unavailable to see the full playbook.

faultline analyze build.log
faultline explain docker-daemon-unavailable

Generated from playbooks/bundled/log/runtime/docker-daemon-unavailable.yaml. Do not edit directly.