GoogleContainerTools/skaffold · error

inferring syncmap for image %q: %w

Error message

inferring syncmap for image %q: %w

What it means

`inferredSyncItem` wraps failures from `SyncMap`, which infers which container paths can be hot-synced by analyzing the image's history/layers. The error means skaffold could not infer a sync map for the image, so automatic (inferred) file sync cannot proceed for the artifact.

Source

Thrown at pkg/skaffold/sync/sync.go:132

		if err != nil {
			return nil, err
		}
		return &Item{
			Image:    tag,
			Artifact: a,
			Copy:     toCopy,
			Delete:   toDelete,
		}, nil
	}

	// deleted files are no longer contained in the syncMap, so we need to rebuild
	if len(e.Deleted) > 0 {
		return nil, nil
	}

	syncMap, err := SyncMap(ctx, a, cfg)
	if err != nil {
		return nil, fmt.Errorf("inferring syncmap for image %q: %w", a.ImageName, err)
	}

	toCopy := make(map[string][]string)
	for _, f := range append(e.Modified, e.Added...) {
		relPath, err := filepath.Rel(a.Workspace, f)
		if err != nil {
			return nil, fmt.Errorf("finding changed file %s relative to context %q: %w", f, a.Workspace, err)
		}

		matches := false
		for _, p := range a.Sync.Infer {
			matches, err = doublestar.PathMatch(filepath.FromSlash(p), relPath)
			if err != nil {
				return nil, fmt.Errorf("pattern error for %q: %w", relPath, err)
			}
			if matches {
				break
			}

View on GitHub (pinned to a1189de023)

Solutions

1. Authenticate to the image's registry (docker login / credential helper) so history can be read.
2. Verify the image exists locally or remotely and the docker daemon is reachable.
3. Define explicit manual sync rules (sync: manual: [...]) in skaffold.yaml to bypass inference.
4. Rebuild the image so fresh, inspectable metadata is available.

Example fix

// before
build:
  artifacts:
    - image: app // inference fails on private base image
// after
build:
  artifacts:
    - image: app
      sync:
        manual:
          - src: 'src/**/*.js'
            dest: /app/src

if _, _, err := exec.Command("docker", "image", "inspect", tag).CombinedOutput(); err != nil {
  // image metadata unreadable: inferred sync will fail, configure manual sync rules instead
  log.Printf("image %s not inspectable; manual sync rules required", tag)
}

item, err := sync.NewItem(ctx, artifact, events, builds, cfg)
if err != nil {
  if strings.Contains(err.Error(), "inferring syncmap") {
    log.Printf("sync inference failed (%v); using manual sync rules or rebuild", err)
    return triggerRebuild(artifact)
  }
  return err
}

When it happens

Trigger: Calling `NewItem` for an artifact using inferred sync where `SyncMap(ctx, a, cfg)` fails — e.g. image metadata is unavailable (image pruned, daemon unreachable), the image history can't be read from the registry due to auth, or the Dockerfile/image format isn't analyzable.

Common situations: Images built with builders whose metadata skaffold can't inspect (e.g. non-Docker builds like Jib/Kaniko output without local layers); private registry requiring docker login; base images from private registries breaking history analysis; docker daemon not running.

Related errors

• copying files: %w
• deleting files: %w
• retrieving working dir for %q: %w
• walking workspace: %w
• could not find latest tag for image %s in builds: %v

AI-assisted analysis of GoogleContainerTools/skaffold@a1189de023 (2026-09-05). Data as JSON: /api/errors/13d8babe3c74d8d1. Report an issue: GitHub.