detect that CentOS 7 uses systemd, write previous-hostname in that case.

Also, on RHEL-type systems using systemd, 
/var/lib/cloud/data/previous-hostname would never get created (because
rather then write to files, it was executing hostnamectl)

2 files changed, 10 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index ff5f2aac..390f2803 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -39,6 +39,7 @@
    [Surojit Pathak]
  - Azure: do not re-set hostname if user has changed it (LP: #1375252)
  - Fix exception when running with no arguments on Python 3. [Daniel Watkins]
+ - Centos: detect/expect use of systemd on centos 7. [Brian Rak]
 0.7.6:
  - open 0.7.6
  - Enable vendordata on CloudSigma datasource (LP: #1303986)
diff --git a/cloudinit/distros/rhel.py b/cloudinit/distros/rhel.py
index 7408989c..eec17c61 100644
--- a/cloudinit/distros/rhel.py
+++ b/cloudinit/distros/rhel.py
@@ -116,6 +116,7 @@ class Distro(distros.Distro):
         (dist, vers) = util.system_info()['dist'][:2]
         major = (int)(vers.split('.')[0])
         return ((dist.startswith('Red Hat Enterprise Linux') and major >= 7)
+                or (dist.startswith('CentOS Linux') and major >= 7)
                 or (dist.startswith('Fedora') and major >= 18))
 
     def apply_locale(self, locale, out_fn=None):
@@ -132,7 +133,11 @@ class Distro(distros.Distro):
         rhel_util.update_sysconfig_file(out_fn, locale_cfg)
 
     def _write_hostname(self, hostname, out_fn):
-        if self.uses_systemd():
+        # systemd will never update previous-hostname for us, so 
+        # we need to do it ourselves
+        if self.uses_systemd() and out_fn.endswith('/previous-hostname'):
+            util.write_file(out_fn, hostname)
+        elif self.uses_systemd():
             util.subp(['hostnamectl', 'set-hostname', str(hostname)])
         else:
             host_cfg = {
@@ -155,7 +160,9 @@ class Distro(distros.Distro):
         return (host_fn, self._read_hostname(host_fn))
 
     def _read_hostname(self, filename, default=None):
-        if self.uses_systemd():
+        if self.uses_systemd() and filename.endswith('/previous-hostname'):
+            return util.load_file(filename).strip()  
+        elif self.uses_systemd():
             (out, _err) = util.subp(['hostname'])
             if len(out):
                 return out