check for systemd using sd_booted() semantics

The existing cloud-init 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, and
- 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

1 files changed, 8 insertions, 0 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index e0cce670..8a947867 100644
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -27,6 +27,7 @@ from six import StringIO
 import abc
 import os
 import re
+import stat
 
 from cloudinit import importer
 from cloudinit import log as logging
@@ -89,6 +90,13 @@ class Distro(object):
         self._write_hostname(writeable_hostname, self.hostname_conf_fn)
         self._apply_hostname(writeable_hostname)
 
+    def uses_systemd(self):
+        try:
+            res = os.lstat('/run/systemd/system')
+            return stat.S_ISDIR(res.st_mode)
+        except:
+            return False
+
     @abc.abstractmethod
     def package_command(self, cmd, args=None, pkgs=None):
         raise NotImplementedError()