slimtoolkit/slim · error

failed to scan files: %w

Error message

failed to scan files: %w

What it means

filepath.Walk over the layer directory returned an error, which is wrapped as "failed to scan files". Note the walk callback swallows per-file errors (returns nil), so this error comes from the walk machinery itself — e.g. the root directory is unreadable — or from any of the wrapped callback errors (relative path, tar header, unsupported type, copy).

Source

Thrown at pkg/imagebuilder/internalbuilder/engine.go:324

		if err := tw.WriteHeader(hdr); err != nil {
			return fmt.Errorf("failed to write tar header: %w", err)
		}
		if !info.IsDir() {
			f, err := os.Open(fp)
			if err != nil {
				return err
			}
			if _, err := io.Copy(tw, f); err != nil {
				return fmt.Errorf("failed to read file into the tar: %w", err)
			}
			f.Close()
		}
		return nil
	})

	if err != nil {
		return nil, fmt.Errorf("failed to scan files: %w", err)
	}
	if err := tw.Close(); err != nil {
		return nil, fmt.Errorf("failed to finish tar: %w", err)
	}

	return tarball.LayerFromReader(&b)
}

View on GitHub (pinned to 81940d17fa)

Solutions

1. Unwrap the error to find the root cause (unsupported file type vs. traversal failure).
2. Remove unsupported file types from the layer directory.
3. Verify read permissions on the layer directory and its contents.

Example fix

// before
os.Chmod("/build/rootfs", 0o000) // walk cannot read root
// after
os.Chmod("/build/rootfs", 0o755)
layerFromDir(LayerDataInfo{Source: "/build/rootfs"})

if info, err := os.Stat(src); err != nil || !info.IsDir() {
    return fmt.Errorf("cannot scan layer dir %q: %v", src, err)
}
if !isReadable(src) { return fmt.Errorf("layer dir not readable: %s", src) }

layer, err := build(ctx, opts)
var pathErr *fs.PathError
if errors.As(err, &pathErr) || strings.Contains(err.Error(), "failed to scan files") {
    // log errors.Unwrap chain, fix perms/unsupported types, retry
}

When it happens

Trigger: Any error escaping the walk callback (unsupported file type 203, header 204, copy 205, relative path 202) or filepath.Walk failing to traverse the root of input.Source.

Common situations: Layer directory containing symlinks/devices (via 203), permission-denied on the layer root, or the directory vanishing mid-build.

Related errors

• failed to calculate relative path: %w
• not implemented archiving file type %s (%s)
• failed to read file into the tar: %w
• bad output tar - %s
• failed to write tar header: %w

AI-assisted analysis of slimtoolkit/slim@81940d17fa (2026-08-31). Data as JSON: /api/errors/3ae7571ee4086cbc. Report an issue: GitHub.