docker/cli · error

writing config to tar file for config copy: %w

Error message

writing config to tar file for config copy: %w

What it means

Error "writing config to tar file for config copy: %w" thrown in docker/cli.

Source

Thrown at cli/command/container/create.go:420

// /root/.docker/config.json.
func copyDockerConfigIntoContainer(ctx context.Context, apiClient client.APIClient, containerID string, configPath string, config *configfile.ConfigFile) error {
	var configBuf bytes.Buffer
	if err := config.SaveToWriter(&configBuf); err != nil {
		return fmt.Errorf("saving creds: %w", err)
	}

	// We don't need to get super fancy with the tar creation.
	var tarBuf bytes.Buffer
	tarWriter := tar.NewWriter(&tarBuf)
	_ = tarWriter.WriteHeader(&tar.Header{
		Name: configPath,
		Size: int64(configBuf.Len()),
		Mode: 0o600,
	})

	if _, err := io.Copy(tarWriter, &configBuf); err != nil {
		_ = tarWriter.Close()
		return fmt.Errorf("writing config to tar file for config copy: %w", err)
	}

	if err := tarWriter.Close(); err != nil {
		return fmt.Errorf("closing tar for config copy failed: %w", err)
	}

	_, err := apiClient.CopyToContainer(ctx, containerID, client.CopyToContainerOptions{
		DestinationPath: "/",
		Content:         &tarBuf,
	})
	if err != nil {
		return fmt.Errorf("copying config.json into container failed: %w", err)
	}

	return nil
}

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at cli/command/container/create.go:420 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/6fe5874b8a728151.json. Report an issue: GitHub.