diff --git a/dvc/repo/experiments/executor.py b/dvc/repo/experiments/executor.py
index 25674d9e2..711b50734 100644
--- a/dvc/repo/experiments/executor.py
+++ b/dvc/repo/experiments/executor.py
@@ -1,6 +1,7 @@
 import logging
 import os
 import pickle
+import sys
 from functools import partial
 from tempfile import TemporaryDirectory
 from typing import TYPE_CHECKING, Callable, Iterable, Optional, Tuple, Union
@@ -343,4 +344,11 @@ class LocalExecutor(BaseExecutor):
     def cleanup(self):
         super().cleanup()
         logger.debug("Removing tmpdir '%s'", self._tmp_dir)
-        self._tmp_dir.cleanup()
+        try:
+            self._tmp_dir.cleanup()
+        except PermissionError:
+            if os.name == "nt" and sys.version_info < (3, 8):
+                # see https://bugs.python.org/issue26660
+                remove(self._tmp_dir.name)
+                return
+            raise
diff --git a/dvc/scm/git/backend/dulwich.py b/dvc/scm/git/backend/dulwich.py
index c8bc9256f..478ea23cd 100644
--- a/dvc/scm/git/backend/dulwich.py
+++ b/dvc/scm/git/backend/dulwich.py
@@ -57,10 +57,28 @@ class DulwichBackend(BaseGitBackend):  # pylint:disable=abstract-method
         return self.repo.commondir()
 
     def add(self, paths: Iterable[str]):
-        raise NotImplementedError
+        from dvc.utils.fs import walk_files
+
+        if isinstance(paths, str):
+            paths = [paths]
+
+        files = []
+        for path in paths:
+            if not os.path.isabs(path):
+                path = os.path.join(self.root_dir, path)
+            if os.path.isdir(path):
+                files.extend(walk_files(path))
+            else:
+                files.append(path)
+
+        for fpath in files:
+            # NOTE: this doesn't check gitignore, same as GitPythonBackend.add
+            self.repo.stage(relpath(fpath, self.root_dir))
 
     def commit(self, msg: str):
-        raise NotImplementedError
+        from dulwich.porcelain import commit
+
+        commit(self.root_dir, message=msg)
 
     def checkout(
         self, branch: str, create_new: Optional[bool] = False, **kwargs,
@@ -83,7 +101,14 @@ class DulwichBackend(BaseGitBackend):  # pylint:disable=abstract-method
         raise NotImplementedError
 
     def is_tracked(self, path: str) -> bool:
-        raise NotImplementedError
+        from dvc.path_info import PathInfo
+
+        rel = PathInfo(path).relative_to(self.root_dir).as_posix().encode()
+        rel_dir = rel + b"/"
+        for path in self.repo.open_index():
+            if path == rel or path.startswith(rel_dir):
+                return True
+        return False
 
     def is_dirty(self, **kwargs) -> bool:
         raise NotImplementedError
diff --git a/tests/func/experiments/test_experiments.py b/tests/func/experiments/test_experiments.py
index 160add628..0955f0b4a 100644
--- a/tests/func/experiments/test_experiments.py
+++ b/tests/func/experiments/test_experiments.py
@@ -235,11 +235,19 @@ def test_update_py_params(tmp_dir, scm, dvc):
         "class Klass:\n    def __init__(self):\n        self.a = 222"
     )
 
+    def _dos2unix(text):
+        if os.name != "nt":
+            return text
+
+        # NOTE: git on windows will use CRLF, so we have to convert it to LF
+        # in order to compare with the original
+        return text.replace("\r\n", "\n")
+
     tree = scm.get_tree(exp_a)
     with tree.open(tmp_dir / "params.py") as fobj:
-        assert fobj.read().strip() == result
+        assert _dos2unix(fobj.read().strip()) == result
     with tree.open(tmp_dir / "metrics.py") as fobj:
-        assert fobj.read().strip() == result
+        assert _dos2unix(fobj.read().strip()) == result
 
     tmp_dir.gen("params.py", "INT = 1\n")
     stage = dvc.run(