GoogleContainerTools/skaffold · error

docker build failure: %w

Error message

docker build failure: %w

What it means

While streaming the build's JSON messages, a *jsonstream.Error was received — the daemon reported the build itself failed (e.g. a RUN command exited non-zero). Skaffold detects the error type via errors.As and rewraps it as `docker build failure` to distinguish a real build failure from a transport problem.

Source

Thrown at pkg/skaffold/docker/image.go:402

	var imageID string
	auxCallback := func(msg jsonstream.Message) {
		if msg.Aux == nil {
			return
		}

		var result BuildResult
		if err := json.Unmarshal(*msg.Aux, &result); err != nil {
			log.Entry(ctx).Debug("Unable to parse build output:", err)
			return
		}
		imageID = result.ID
	}

	if err := streamDockerMessages(out, resp.Body, auxCallback); err != nil {
		var jm *jsonstream.Error
		if errors.As(err, &jm) {
			return "", fmt.Errorf("docker build failure: %w", err)
		}
		return "", fmt.Errorf("unable to stream build output: %w", err)
	}

	if imageID == "" {
		// Maybe this version of Docker doesn't return the digest of the image
		// that has been built.
		imageID, err = l.ImageID(ctx, opts.Tag)
		if err != nil {
			return "", fmt.Errorf("getting digest: %w", err)
		}
	}

	return imageID, nil
}

// streamDockerMessages streams formatted json output from the docker daemon
func streamDockerMessages(dst io.Writer, src io.Reader, auxCallback func(jsonstream.Message)) error {

View on GitHub (pinned to a1189de023)

Solutions

1. Read the wrapped jsonstream error output to find the failing Dockerfile step
2. Fix the failing instruction in the Dockerfile
3. Rebuild with --no-cache if a cached layer masks the issue
4. Check base image names/tags and registry authentication

Example fix

// before
RUN npm test   # failing step
// after
RUN npm run build   # corrected/removed failing step

var jm *jsonstream.Error
if err := ...; errors.As(err, &jm) {
	// inspect jm for the failing Dockerfile step and fix the Dockerfile
	return fmt.Errorf("build step failed: %v", jm)
}

When it happens

Trigger: streamDockerMessages returns a *jsonstream.Error, i.e. the Docker daemon sent an error message during the build — a failing RUN/COPY step, exit code != 0 in a Dockerfile instruction, or a step the daemon could not execute.

Common situations: Dockerfile bug (typo in package name, failing test in RUN); missing base image or registry auth; COPY of a file excluded by .dockerignore; disk full on the daemon host.

Related errors

• normalizing dockerfile path: %w
• reading dockerfile: %w
• removing unused default args: %w
• normalizing dockerfilePath path: %w
• normalizing dockerfile path: %w

AI-assisted analysis of GoogleContainerTools/skaffold@a1189de023 (2026-09-05). Data as JSON: /api/errors/c31053a2caa0c27a. Report an issue: GitHub.