check for systemd using sd_booted() semantics

The existing code determines if systemd is in use by looking at the
distribution name and version. This is prone to error because:
- RHEL derivatives other than CentOS (e.g., Scientific Linux) will fail
  this test
- Distributions that are not derived from RHEL also use systemd

This patch makes cloud-init use the same logic that is used in systemd's
sd_booted() method
 http://www.freedesktop.org/software/systemd/man/sd_booted.html

LP: #1461201

2 files changed, 29 insertions, 4 deletions

diff --git a/tests/unittests/helpers.py b/tests/unittests/helpers.py
index 61a1f6ff..7f4b8784 100644
--- a/tests/unittests/helpers.py
+++ b/tests/unittests/helpers.py
@@ -248,13 +248,15 @@ class FilesystemMockingTestCase(ResourceUsingTestCase):
 
     def patchOS(self, new_root):
         patch_funcs = {
-            os.path: ['isfile', 'exists', 'islink', 'isdir'],
-            os: ['listdir'],
+            os.path: [('isfile', 1), ('exists', 1),
+                      ('islink', 1), ('isdir', 1)],
+            os: [('listdir', 1), ('mkdir', 1),
+                 ('lstat', 1), ('symlink', 2)],
         }
         for (mod, funcs) in patch_funcs.items():
-            for f in funcs:
+            for f, nargs in funcs:
                 func = getattr(mod, f)
-                trap_func = retarget_many_wrapper(new_root, 1, func)
+                trap_func = retarget_many_wrapper(new_root, nargs, func)
                 self.patched_funcs.enter_context(
                     mock.patch.object(mod, f, trap_func))
 
diff --git a/tests/unittests/test_distros/test_generic.py b/tests/unittests/test_distros/test_generic.py
index 35153f0d..8e3bd78a 100644
--- a/tests/unittests/test_distros/test_generic.py
+++ b/tests/unittests/test_distros/test_generic.py
@@ -194,6 +194,29 @@ class TestGenericDistro(helpers.FilesystemMockingTestCase):
                          {'primary': 'http://fs-primary-intel',
                           'security': 'http://security-mirror2-intel'})
 
+    def test_systemd_in_use(self):
+        cls = distros.fetch("ubuntu")
+        d = cls("ubuntu", {}, None)
+        self.patchOS(self.tmp)
+        self.patchUtils(self.tmp)
+        os.makedirs('/run/systemd/system')
+        self.assertTrue(d.uses_systemd())
+
+    def test_systemd_not_in_use(self):
+        cls = distros.fetch("ubuntu")
+        d = cls("ubuntu", {}, None)
+        self.patchOS(self.tmp)
+        self.patchUtils(self.tmp)
+        self.assertFalse(d.uses_systemd())
+
+    def test_systemd_symlink(self):
+        cls = distros.fetch("ubuntu")
+        d = cls("ubuntu", {}, None)
+        self.patchOS(self.tmp)
+        self.patchUtils(self.tmp)
+        os.makedirs('/run/systemd')
+        os.symlink('/', '/run/systemd/system')
+        self.assertFalse(d.uses_systemd())
 
 # def _get_package_mirror_info(mirror_info, availability_zone=None,
 #                             mirror_filter=util.search_for_mirror):