cloud-init-dev team mailing list archive

[Robert Schweikert <rjschwei@xxxxxxxx>]

Robert Schweikert has proposed merging ~rjschwei/cloud-init:noEmptyResolv into cloud-init:master.

Requested reviews:
  cloud-init commiters (cloud-init-dev)
Related bugs:
  Bug #1812853 in cloud-init: "should not write an "empty" resolve.conf file"
  https://bugs.launchpad.net/cloud-init/+bug/1812853

For more details, see:
https://code.launchpad.net/~rjschwei/cloud-init/+git/cloud-init/+merge/362132

DO not write a resolv.conf file with only the header. Writing the file with no dns information may provide distro tools from writing a resolv.conf file with dns information obtained from a dhcp server
-- 
Your team cloud-init commiters is requested to review the proposed merge of ~rjschwei/cloud-init:noEmptyResolv into cloud-init:master.

diff --git a/cloudinit/net/sysconfig.py b/cloudinit/net/sysconfig.py
index ae41f7b..817441c 100644
--- a/cloudinit/net/sysconfig.py
+++ b/cloudinit/net/sysconfig.py
@@ -557,6 +557,8 @@ class Renderer(renderer.Renderer):
             content.add_nameserver(nameserver)
         for searchdomain in network_state.dns_searchdomains:
             content.add_search_domain(searchdomain)
+        if not str(content):
+            return str(content)
         header = _make_header(';')
         content_str = str(content)
         if not content_str.startswith(header):
@@ -666,7 +668,8 @@ class Renderer(renderer.Renderer):
             dns_path = util.target_path(target, self.dns_path)
             resolv_content = self._render_dns(network_state,
                                               existing_dns_path=dns_path)
-            util.write_file(dns_path, resolv_content, file_mode)
+            if resolv_content:
+                util.write_file(dns_path, resolv_content, file_mode)
         if self.networkmanager_conf_path:
             nm_conf_path = util.target_path(target,
                                             self.networkmanager_conf_path)
diff --git a/tests/unittests/test_net.py b/tests/unittests/test_net.py
index d679e92..8c52753 100644
--- a/tests/unittests/test_net.py
+++ b/tests/unittests/test_net.py
@@ -2098,6 +2098,10 @@ TYPE=Ethernet
 USERCTL=no
 """
         self.assertEqual(expected, found[nspath + 'ifcfg-interface0'])
+        # The configuration has no nameserver information make sure we
+        # do not write the resolv.conf file
+        respath = '/etc/resolv.conf'
+        self.assertNotIn(respath, found.keys())
 
     def test_config_with_explicit_loopback(self):
         ns = network_state.parse_net_config_data(CONFIG_V1_EXPLICIT_LOOPBACK)