diff --git a/moulinette/utils/filesystem.py b/moulinette/utils/filesystem.py
index c86d65ed..d0174b71 100644
--- a/moulinette/utils/filesystem.py
+++ b/moulinette/utils/filesystem.py
@@ -1,13 +1,13 @@
 # encoding: utf-8
 
 import os
-import yaml
 import errno
 import shutil
 import json
-import grp
+import yaml
 
-from pwd import getpwnam
+import grp
+import pwd
 
 from moulinette import m18n
 from moulinette.globals import CACHE_DIR
@@ -91,6 +91,11 @@ def read_yaml(file_path):
                               m18n.g('corrupted_yaml',
                                      ressource=file_path, error=str(e)))
 
+    except yaml.parser.ParserError as e:
+        raise MoulinetteError(errno.EINVAL,
+                              m18n.g('corrupted_yaml',
+                                     ressource=file_path, error=str(e)))
+
     return loaded_yaml
 
 
@@ -217,7 +222,7 @@ def chown(path, uid=None, gid=None, recursive=False):
     # Retrieve uid/gid
     if isinstance(uid, str):
         try:
-            uid = getpwnam(uid).pw_uid
+            uid = pwd.getpwnam(uid).pw_uid
         except KeyError:
             raise MoulinetteError(errno.EINVAL,
                                   m18n.g('unknown_user', user=uid))
diff --git a/tests/moulinette/utils/test_filesystem.py b/tests/moulinette/utils/test_filesystem.py
index 9a4fe1f2..db5ed221 100644
--- a/tests/moulinette/utils/test_filesystem.py
+++ b/tests/moulinette/utils/test_filesystem.py
@@ -111,7 +111,7 @@ def test_read_yaml_return_file_content_as_yaml(open, isfile):
 
 @mock.patch('os.path.isfile')
 @mock.patch('builtins.open')
-def test_read_yaml_raise_error_on_bad_content(open, isfile):
+def test_read_yaml_raise_error_on_very_bad_content(open, isfile):
     isfile.return_value = True
     file_content = 'foo, bar-\n t:'
     open.return_value = fake_open_for_read(file_content)
@@ -120,6 +120,17 @@ def test_read_yaml_raise_error_on_bad_content(open, isfile):
         content = filesystem.read_yaml('bad_file.yaml')
 
 
+@mock.patch('os.path.isfile')
+@mock.patch('builtins.open')
+def test_read_yaml_raise_error_on_bad_content(open, isfile):
+    isfile.return_value = True
+    file_content = 'foo: bar-\n- to'
+    open.return_value = fake_open_for_read(file_content)
+
+    with pytest.raises(MoulinetteError):
+        content = filesystem.read_yaml('bad_file.yaml')
+
+
 ########################################################################
 # Test writing a file
 ########################################################################
@@ -129,7 +140,7 @@ def test_read_yaml_raise_error_on_bad_content(open, isfile):
 
 @mock.patch('os.path.isdir')
 @mock.patch('builtins.open')
-def test_write_to_file_update_file_content(open, isdir):
+def test_write_to_file_update_file_content_with_string(open, isdir):
     # WARNING order is dependant on actual implementation
     isdir.side_effect = [False, True]
     open.return_value, fake_file = fake_open_for_write()
@@ -140,6 +151,20 @@ def test_write_to_file_update_file_content(open, isdir):
     fake_file.write.assert_called_with(content)
 
 
+@mock.patch('os.path.isdir')
+@mock.patch('builtins.open')
+def test_write_to_file_update_file_content_with_list_of_string(open, isdir):
+    # WARNING order is dependant on actual implementation
+    isdir.side_effect = [False, True]
+    open.return_value, fake_file = fake_open_for_write()
+    content = ['some', 'content']
+
+    filesystem.write_to_file('fake/file.txt', content)
+
+    expected_content = 'some\ncontent'
+    fake_file.write.assert_called_with(expected_content)
+
+
 @mock.patch('os.path.isdir')
 @mock.patch('builtins.open')
 def test_write_to_file_raise_error_for_folder_used_as_file(open, isdir):
@@ -413,7 +438,6 @@ def test_chmod_recursive_update_folder_permissions(chmod, isdir, walk):
     calls = [mock.call('folder', mode),
              mock.call('folder/subfolder', mode),
              mock.call('folder/file.txt', mode)]
-
     chmod.assert_has_calls(calls)
 
 
@@ -432,8 +456,123 @@ def test_chmod_recursive_update_folder_permissions_with_fmode(chmod, isdir, walk
     calls = [mock.call('folder', mode),
              mock.call('folder/subfolder', mode),
              mock.call('folder/file.txt', fmode)]
-
     chmod.assert_has_calls(calls)
 
 
+########################################################################
+# Chagin owner of file or folder
+########################################################################
+
+def test_chown_cannot_change_owner_without_providing_uid_or_guid():
+    filename = 'file.txt'
+
+    with pytest.raises(ValueError):
+        filesystem.chown(filename)
+
+
+@mock.patch('os.chown')
+def test_chown_change_owner_of_file_with_given_uid_as_id(chown):
+    filename = 'file.txt'
+    uid = 1000
+
+    filesystem.chown(filename, uid=uid)
+
+    chown.assert_called_with(filename, uid, -1)
+
+@mock.patch('pwd.getpwnam')
+@mock.patch('os.chown')
+def test_chown_change_owner_of_file_with_given_uid_as_name(chown, getpwnam):
+    filename = 'file.txt'
+    name = 'jdoe'
+    uid = 1000
+    getpwnam.return_value = mock.Mock(pw_uid=uid)
+
+    filesystem.chown(filename, uid=name)
+
+    chown.assert_called_with(filename, uid, -1)
+
+
+@mock.patch('pwd.getpwnam')
+@mock.patch('os.chown')
+def test_cannot_change_owner_of_file_with_unknown_user_name(chown, getpwnam):
+    filename = 'file.txt'
+    name = 'jdoe'
+    getpwnam.side_effect = KeyError
+
+    with pytest.raises(MoulinetteError):
+        filesystem.chown(filename, uid=name)
+
+
+@mock.patch('os.chown')
+def test_chown_change_owner_of_file_with_given_gid_as_id(chown):
+    filename = 'file.txt'
+    gid = 1000
+
+    filesystem.chown(filename, gid=gid)
+
+    chown.assert_called_with(filename, -1, gid)
+
+
+@mock.patch('grp.getgrnam')
+@mock.patch('os.chown')
+def test_chown_change_owner_of_file_with_given_gid_as_name(chown, getgrnam):
+    filename = 'file.txt'
+    name = 'jdoe'
+    gid = 1000
+    getgrnam.return_value = mock.Mock(gr_gid=gid)
+
+    filesystem.chown(filename, gid=name)
+
+    chown.assert_called_with(filename, -1, gid)
+
+
+@mock.patch('grp.getgrnam')
+@mock.patch('os.chown')
+def test_cannot_change_owner_of_file_with_unknown_group_name(chown, getgrnam):
+    filename = 'file.txt'
+    name = 'jdoe'
+    getgrnam.side_effect = KeyError
+
+    with pytest.raises(MoulinetteError):
+        filesystem.chown(filename, gid=name)
+
+
+@mock.patch('os.chown')
+def test_chown_cannot_change_owner_of_file_without_permission(chown):
+    filename = 'file.txt'
+    gid = 1000
+    chown.side_effect = PermissionError
+
+    with pytest.raises(MoulinetteError):
+        filesystem.chown(filename, gid=gid)
+
+
+@mock.patch('os.chown')
+def test_chown_cannot_change_owner_of_non_existant_file(chown):
+    filename = 'file.txt'
+    gid = 1000
+    chown.side_effect = FileNotFoundError
+
+    with pytest.raises(MoulinetteError):
+        filesystem.chown(filename, gid=gid)
+
+
+@mock.patch('os.walk')
+@mock.patch('os.path.isdir')
+@mock.patch('os.chown')
+def test_chown_recursive_update_folder_owner(chown, isdir, walk):
+    foldername = 'folder'
+    uid = 1000
+    gid = 1000
+    isdir.return_value = True  # foldername is a folder
+    walk.return_value = [(foldername, ['subfolder'], ['file.txt'])]
+
+    filesystem.chown(foldername, uid=uid, gid=gid, recursive=True)
+
+    calls = [mock.call('folder', uid, gid),
+             mock.call('folder/subfolder', uid, gid),
+             mock.call('folder/file.txt', uid, gid)]
+    chown.assert_has_calls(calls)
+
+
 # eof