GoogleContainerTools/skaffold · error

extracting sync rules from labels for %q: %w

Error message

extracting sync rules from labels for %q: %w

What it means

For buildpack artifacts, autoSyncItem extracts container filesystem sync rules (which files to copy/delete) from the image's buildpack metadata labels. If buildpacks.SyncRules cannot parse those labels (missing or malformed lifecycle metadata), Skaffold returns this wrapped error.

Source

Thrown at pkg/skaffold/sync/sync.go:197

	case a.KanikoArtifact != nil:
		return docker.SyncMap(ctx, a.Workspace, a.KanikoArtifact.DockerfilePath, a.KanikoArtifact.BuildArgs, cfg)

	default:
		return nil, build.ErrSyncMapNotSupported{}
	}
}

func autoSyncItem(ctx context.Context, a *latest.Artifact, tag string, e filemon.Events, cfg docker.Config) (*Item, error) {
	switch {
	case a.BuildpackArtifact != nil:
		labels, err := Labels(ctx, tag, cfg)
		if err != nil {
			return nil, fmt.Errorf("retrieving labels for %q: %w", tag, err)
		}

		rules, err := buildpacks.SyncRules(labels)
		if err != nil {
			return nil, fmt.Errorf("extracting sync rules from labels for %q: %w", tag, err)
		}

		return syncItem(ctx, a, tag, e, rules, cfg)

	case a.JibArtifact != nil:
		toCopy, toDelete, err := jib.GetSyncDiff(ctx, a.Workspace, a.JibArtifact, e)
		if err != nil {
			return nil, err
		}
		if toCopy == nil && toDelete == nil {
			// do a rebuild
			return nil, nil
		}
		return &Item{Image: tag, Artifact: a, Copy: toCopy, Delete: toDelete}, nil

	default:
		// TODO: this error does appear a little late in the build, perhaps it could surface at first run, rather than first sync?
		return nil, fmt.Errorf("Sync: Auto is not supported by the build of %s", a.ImageName)

View on GitHub (pinned to a1189de023)

Solutions

1. Rebuild the image with `pack build` using a current CNB-compliant builder so lifecycle labels are present
2. Confirm the artifact really is a buildpack build in skaffold.yaml; if not, switch the build type or use explicit `sync.manual` rules instead of auto sync
3. Inspect labels with `docker image inspect <tag> --format '{{json .Config.Labels}}'` and verify io.buildpacks lifecycle JSON parses

Example fix

// before (docker-built image but buildpack artifact config)
build:
  artifacts:
    - image: app
      buildpacks: {builder: ""}
// after
build:
  artifacts:
    - image: app
      buildpacks:
        builder: paketobuildpacks/builder:base

labels, err := sync.Labels(ctx, tag, cfg)
if err != nil { return err }
if _, err := buildpacks.SyncRules(labels); err != nil { return err }

item, err := sync.NewItem(ctx, a, tag, e, cfg, builds)
if err != nil { return err }

When it happens

Trigger: The image referenced by `tag` lacks well-formed `io.buildpacks.*` label JSON — e.g. built by a non-CNB builder, built with an unsupported lifecycle version, or the labels were stripped by a registry/rewrite step.

Common situations: Pointing skaffold at an image built outside pack (plain docker build) but configured as a buildpack artifact; migrating to a new pack/CLI version with changed label schema; using a builder image whose lifecycle metadata is outdated.

Related errors

• retrieving labels for %q: %w
• failed to execute host %s hook %d for artifact %q: %w
• failed to execute container %s hook %d for artifact %q: %w
• exiting dev mode because initializing sync state failed: %w
• finding changed file %s relative to context %q: %w

AI-assisted analysis of GoogleContainerTools/skaffold@a1189de023 (2026-09-05). Data as JSON: /api/errors/e72529e5e4eb54c4. Report an issue: GitHub.