feat: Add an command line option to exclude root directory in the tarball

Fixes GoogleContainerTools#1375

Signed-off-by: Zhiyuan Chen <[email protected]>

Author: zhiyuan-chn

Diff for: README.md

@@ -80,6 +80,7 @@ _If you are interested in contributing to kaniko, see
       - [Flag `--custom-platform`](#flag---custom-platform)
       - [Flag `--digest-file`](#flag---digest-file)
       - [Flag `--dockerfile`](#flag---dockerfile)
+      - [Flag `--exclude-root-dir-tarball`](#flag---exclude-root-dir-tarball)
       - [Flag `--force`](#flag---force)
       - [Flag `--git`](#flag---git)
       - [Flag `--image-name-with-digest-file`](#flag---image-name-with-digest-file)
@@ -891,6 +892,10 @@ the digest to that file, which is picked up by Kubernetes automatically as the
 
 Path to the dockerfile to be built. (default "Dockerfile")
 
+#### Flag `--exclude-root-dir-tarball`
+
+Set this flag to exclude root directory in tar archive. This can enable tools like Flux that use non-GNU tar to extract images created by Kaniko.
+
 #### Flag `--force`
 
 Force building outside of a container

Diff for: cmd/executor/cmd/root.go

@@ -280,6 +280,7 @@ func addKanikoOptionsFlags() {
 	RootCmd.PersistentFlags().VarP(&opts.IgnorePaths, "ignore-path", "", "Ignore these paths when taking a snapshot. Set it repeatedly for multiple paths.")
 	RootCmd.PersistentFlags().BoolVarP(&opts.ForceBuildMetadata, "force-build-metadata", "", false, "Force add metadata layers to build image")
 	RootCmd.PersistentFlags().BoolVarP(&opts.SkipPushPermissionCheck, "skip-push-permission-check", "", false, "Skip check of the push permission")
+	RootCmd.PersistentFlags().BoolVarP(&opts.ExcludeRootDirTarball, "exclude-root-dir-tarball", "", false, "Exclude root directory in tarball")
 
 	// Deprecated flags.
 	RootCmd.PersistentFlags().StringVarP(&opts.SnapshotModeDeprecated, "snapshotMode", "", "", "This flag is deprecated. Please use '--snapshot-mode'.")

Diff for: pkg/config/options.go

@@ -91,6 +91,7 @@ type KanikoOptions struct {
 	ForceBuildMetadata       bool
 	InitialFSUnpacked        bool
 	SkipPushPermissionCheck  bool
+	ExcludeRootDirTarball    bool
 }
 
 type KanikoGitOptions struct {

Diff for: pkg/executor/build.go

@@ -112,6 +112,7 @@ func newStageBuilder(args *dockerfile.BuildArgs, opts *config.KanikoOptions, sta
 	}
 	l := snapshot.NewLayeredMap(hasher)
 	snapshotter := snapshot.NewSnapshotter(l, config.RootDir)
+	snapshotter.SetExcludeRootDirTarball(opts.ExcludeRootDirTarball)
 
 	digest, err := sourceImage.Digest()
 	if err != nil {

Diff for: pkg/snapshot/snapshot.go

@@ -39,9 +39,10 @@ var snapshotPathPrefix = ""
 
 // Snapshotter holds the root directory from which to take snapshots, and a list of snapshots taken
 type Snapshotter struct {
-	l          *LayeredMap
-	directory  string
-	ignorelist []util.IgnoreListEntry
+	l                     *LayeredMap
+	directory             string
+	ignorelist            []util.IgnoreListEntry
+	excludeRootDirTarball bool
 }
 
 // NewSnapshotter creates a new snapshotter rooted at d
@@ -114,7 +115,7 @@ func (s *Snapshotter) TakeSnapshot(files []string, shdCheckDelete bool, forceBui
 
 	t := util.NewTar(f)
 	defer t.Close()
-	if err := writeToTar(t, filesToAdd, filesToWhiteout); err != nil {
+	if err := writeToTar(t, filesToAdd, filesToWhiteout, s.excludeRootDirTarball); err != nil {
 		return "", err
 	}
 	return f.Name(), nil
@@ -136,12 +137,17 @@ func (s *Snapshotter) TakeSnapshotFS() (string, error) {
 		return "", err
 	}
 
-	if err := writeToTar(t, filesToAdd, filesToWhiteOut); err != nil {
+	if err := writeToTar(t, filesToAdd, filesToWhiteOut, s.excludeRootDirTarball); err != nil {
 		return "", err
 	}
 	return f.Name(), nil
 }
 
+// SetExcludeRootDirTarball sets the flag to exclude root directory from the tar archive.
+func (s *Snapshotter) SetExcludeRootDirTarball(e bool) {
+	s.excludeRootDirTarball = e
+}
+
 func (s *Snapshotter) getSnashotPathPrefix() string {
 	if snapshotPathPrefix == "" {
 		return config.KanikoDir
@@ -230,7 +236,7 @@ func removeObsoleteWhiteouts(deletedFiles map[string]struct{}) (filesToWhiteout
 	return filesToWhiteout
 }
 
-func writeToTar(t util.Tar, files, whiteouts []string) error {
+func writeToTar(t util.Tar, files, whiteouts []string, excludeRootDirTarball bool) error {
 	timer := timing.Start("Writing tar file")
 	defer timing.DefaultRun.Stop(timer)
 
@@ -246,7 +252,7 @@ func writeToTar(t util.Tar, files, whiteouts []string) error {
 			continue
 		}
 
-		if err := addParentDirectories(t, addedPaths, path); err != nil {
+		if err := addParentDirectories(t, addedPaths, path, excludeRootDirTarball); err != nil {
 			return err
 		}
 		if err := t.Whiteout(path); err != nil {
@@ -255,12 +261,15 @@ func writeToTar(t util.Tar, files, whiteouts []string) error {
 	}
 
 	for _, path := range files {
-		if err := addParentDirectories(t, addedPaths, path); err != nil {
+		if err := addParentDirectories(t, addedPaths, path, excludeRootDirTarball); err != nil {
 			return err
 		}
 		if _, pathAdded := addedPaths[path]; pathAdded {
 			continue
 		}
+		if path == config.RootDir && excludeRootDirTarball {
+			continue
+		}
 		if err := t.AddFileToTar(path); err != nil {
 			return err
 		}
@@ -284,11 +293,14 @@ func parentPathIncludesNonDirectory(path string) (bool, error) {
 	return false, nil
 }
 
-func addParentDirectories(t util.Tar, addedPaths map[string]bool, path string) error {
+func addParentDirectories(t util.Tar, addedPaths map[string]bool, path string, excludeRootDirTarball bool) error {
 	for _, parentPath := range util.ParentDirectories(path) {
 		if _, pathAdded := addedPaths[parentPath]; pathAdded {
 			continue
 		}
+		if parentPath == config.RootDir && excludeRootDirTarball {
+			continue
+		}
 		if err := t.AddFileToTar(parentPath); err != nil {
 			return err
 		}