hostname: apply hostname same as is written

on RHEL, we were writing to persistent configuration the fqdn, but
invoking 'hostname' on the first boot with just the shortname.  On 'reboot',
then the hostname would differ.

Now, whatever we write, invoke hostname with.

Also remove some duplicate code.

LP: #1246485

1 files changed, 6 insertions, 3 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index bf465442..5eab780b 100644
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -86,7 +86,7 @@ class Distro(object):
     def set_hostname(self, hostname, fqdn=None):
         writeable_hostname = self._select_hostname(hostname, fqdn)
         self._write_hostname(writeable_hostname, self.hostname_conf_fn)
-        self._apply_hostname(hostname)
+        self._apply_hostname(writeable_hostname)
 
     @abc.abstractmethod
     def package_command(self, cmd, args=None, pkgs=None):
@@ -160,9 +160,12 @@ class Distro(object):
             util.logexc(LOG, "Failed to non-persistently adjust the system "
                         "hostname to %s", hostname)
 
-    @abc.abstractmethod
     def _select_hostname(self, hostname, fqdn):
-        raise NotImplementedError()
+        # Prefer the short hostname over the long
+        # fully qualified domain name
+        if not hostname:
+            return fqdn
+        return hostname
 
     @staticmethod
     def expand_osfamily(family_list):