skip snapshotting rootdir

integration/dockerfiles/Dockerfile_test_root

@@ -0,0 +1,6 @@
+FROM debian
+
+RUN chmod 700 /
+RUN chmod 755 /
+RUN chown 1000:1000 /
+RUN chown root:root /

integration/images.go

@@ -110,6 +110,8 @@ var diffArgsMap = map[string][]string{
 	"TestRun/test_Dockerfile_test_multistage":   {"--extra-ignore-files=new"},
 	// when we untar we overwrite the parent directory, buildkit doesnt
 	"TestRun/test_Dockerfile_test_add": {"--extra-ignore-file-permissions"},
+	// Verify we don't store root directory
+	"TestRun/test_Dockerfile_test_root": {"--extra-ignore-layer-length-mismatch=false"},
 	// FROM scratch we start with root, buildkit doesnt
 	"TestRun/test_Dockerfile_test_workdir_with_user": {"--extra-ignore-file-permissions"},
 	// We don't handle user nobody=-1 nogroup=-1 correctly

pkg/snapshot/snapshot.go

@@ -244,6 +244,7 @@ func writeToTar(t util.Tar, files, whiteouts []string) error {
 
 	// Now create the tar.
 	addedPaths := make(map[string]bool)
+	addedPaths[config.RootDir] = true
 
 	for _, path := range whiteouts {
 		skipWhiteout, err := parentPathIncludesNonDirectory(path)
@@ -294,6 +295,9 @@ func parentPathIncludesNonDirectory(path string) (bool, error) {
 
 func addParentDirectories(t util.Tar, addedPaths map[string]bool, path string) error {
 	for _, parentPath := range util.ParentDirectories(path) {
+		if parentPath == config.RootDir {
+			continue
+		}
 		if _, pathAdded := addedPaths[parentPath]; pathAdded {
 			continue
 		}

pkg/snapshot/snapshot_test.go

@@ -65,8 +65,7 @@ func TestSnapshotFSFileChange(t *testing.T) {
 		batPath: "baz",
 	}
 	for _, path := range util.ParentDirectoriesWithoutLeadingSlash(batPath) {
-		if path == "/" {
-			snapshotFiles["/"] = ""
+		if path == config.RootDir {
 			continue
 		}
 		snapshotFiles[path+"/"] = ""
@@ -155,8 +154,7 @@ func TestSnapshotFSChangePermissions(t *testing.T) {
 		batPathWithoutLeadingSlash: "baz2",
 	}
 	for _, path := range util.ParentDirectoriesWithoutLeadingSlash(batPathWithoutLeadingSlash) {
-		if path == "/" {
-			snapshotFiles["/"] = ""
+		if path == config.RootDir {
 			continue
 		}
 		snapshotFiles[path+"/"] = ""
@@ -225,6 +223,9 @@ func TestSnapshotFSReplaceDirWithLink(t *testing.T) {
 		filepath.Join(testDirWithoutLeadingSlash, "foo"),
 	}
 	for _, path := range util.ParentDirectoriesWithoutLeadingSlash(filepath.Join(testDir, "foo")) {
+		if path == config.RootDir {
+			continue
+		}
 		expectedFiles = append(expectedFiles, strings.TrimRight(path, "/")+"/")
 	}
 
@@ -260,6 +261,9 @@ func TestSnapshotFiles(t *testing.T) {
 		filepath.Join(testDirWithoutLeadingSlash, "foo"),
 	}
 	for _, path := range util.ParentDirectoriesWithoutLeadingSlash(filepath.Join(testDir, "foo")) {
+		if path == config.RootDir {
+			continue
+		}
 		expectedFiles = append(expectedFiles, strings.TrimRight(path, "/")+"/")
 	}
 
@@ -456,7 +460,6 @@ func TestSnapshotIncludesParentDirBeforeWhiteoutFile(t *testing.T) {
 		filepath.Join(testDirWithoutLeadingSlash, "kaniko/.wh.file"),
 		filepath.Join(testDirWithoutLeadingSlash, "kaniko/new-file"),
 		filepath.Join(testDirWithoutLeadingSlash, ".wh.bar"),
-		"/",
 	}
 	for parentDir := filepath.Dir(expectedFiles[0]); parentDir != "."; parentDir = filepath.Dir(parentDir) {
 		expectedFiles = append(expectedFiles, parentDir+"/")

pkg/util/tar_util.go

@@ -103,13 +103,13 @@ func (t *Tar) AddFileToTar(p string) error {
 	}
 
 	if p == config.RootDir {
-		// allow entry for / to preserve permission changes etc. (currently ignored anyway by Docker runtime)
-		hdr.Name = "/"
-	} else {
-		// Docker uses no leading / in the tarball
-		hdr.Name = strings.TrimPrefix(p, config.RootDir)
-		hdr.Name = strings.TrimLeft(hdr.Name, "/")
+		logrus.Panic("Unreachable Code: We should no longer snapshot '/' as it will be ignored by docker anyways")
 	}
+
+	// Docker uses no leading / in the tarball
+	hdr.Name = strings.TrimPrefix(p, config.RootDir)
+	hdr.Name = strings.TrimLeft(hdr.Name, "/")
+
 	if hdr.Typeflag == tar.TypeDir && !strings.HasSuffix(hdr.Name, "/") {
 		hdr.Name = hdr.Name + "/"
 	}