add prefer_fqdn_over_hostname config option (#859)

the above option allows the user to control the behavior of a distro
hostname selection if both short hostname and FQDN are supplied.
If `prefer_fqdn_over_hostname` is true the FQDN will be selected as
hostname; if false the hostname will be selected

LP: #1921004

1 files changed, 7 insertions, 0 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 220bd11f..8b8a647d 100755
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -79,6 +79,7 @@ class Distro(persistence.CloudInitPickleMixin, metaclass=abc.ABCMeta):
     shutdown_options_map = {'halt': '-H', 'poweroff': '-P', 'reboot': '-r'}
 
     _ci_pkl_version = 1
+    prefer_fqdn = False
 
     def __init__(self, name, cfg, paths):
         self._paths = paths
@@ -131,6 +132,9 @@ class Distro(persistence.CloudInitPickleMixin, metaclass=abc.ABCMeta):
     def get_option(self, opt_name, default=None):
         return self._cfg.get(opt_name, default)
 
+    def set_option(self, opt_name, value=None):
+        self._cfg[opt_name] = value
+
     def set_hostname(self, hostname, fqdn=None):
         writeable_hostname = self._select_hostname(hostname, fqdn)
         self._write_hostname(writeable_hostname, self.hostname_conf_fn)
@@ -259,6 +263,9 @@ class Distro(persistence.CloudInitPickleMixin, metaclass=abc.ABCMeta):
     def _select_hostname(self, hostname, fqdn):
         # Prefer the short hostname over the long
         # fully qualified domain name
+        if util.get_cfg_option_bool(self._cfg, "prefer_fqdn_over_hostname",
+                                    self.prefer_fqdn) and fqdn:
+            return fqdn
         if not hostname:
             return fqdn
         return hostname