Implement ntp client spec with auto support for distro selection

Add a base NTP client configuration dictionary and allow Distro
specific changes to be merged.  Add a select client function which
implements logic to preferr installed clients over clients which
need to be installed.  Also allow distributions to override the
cloud-init defaults.

LP: #1749722

10 files changed, 655 insertions, 303 deletions

diff --git a/tests/cloud_tests/testcases/modules/ntp.yaml b/tests/cloud_tests/testcases/modules/ntp.yaml
index 2530d72e..7ea0707d 100644
--- a/tests/cloud_tests/testcases/modules/ntp.yaml
+++ b/tests/cloud_tests/testcases/modules/ntp.yaml
@@ -4,6 +4,7 @@
 cloud_config: |
   #cloud-config
   ntp:
+    ntp_client: ntp
     pools: []
     servers: []
 collect_scripts:
diff --git a/tests/cloud_tests/testcases/modules/ntp_chrony.py b/tests/cloud_tests/testcases/modules/ntp_chrony.py
new file mode 100644
index 00000000..461630a8
--- /dev/null
+++ b/tests/cloud_tests/testcases/modules/ntp_chrony.py
@@ -0,0 +1,15 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+"""cloud-init Integration Test Verify Script."""
+from tests.cloud_tests.testcases import base
+
+
+class TestNtpChrony(base.CloudTestCase):
+    """Test ntp module with chrony client"""
+
+    def test_chrony_entires(self):
+        """Test chrony config entries"""
+        out = self.get_data_file('chrony_conf')
+        self.assertIn('.pool.ntp.org', out)
+
+# vi: ts=4 expandtab
diff --git a/tests/cloud_tests/testcases/modules/ntp_chrony.yaml b/tests/cloud_tests/testcases/modules/ntp_chrony.yaml
new file mode 100644
index 00000000..120735e2
--- /dev/null
+++ b/tests/cloud_tests/testcases/modules/ntp_chrony.yaml
@@ -0,0 +1,17 @@
+#
+# ntp enabled, chrony selected, check conf file
+# as chrony won't start in a container
+#
+cloud_config: |
+  #cloud-config
+  ntp:
+    enabled: true
+    ntp_client: chrony
+collect_scripts:
+  chrony_conf: |
+    #!/bin/sh
+    set -- /etc/chrony.conf /etc/chrony/chrony.conf
+    for p in "$@"; do
+        [ -e "$p" ] && { cat "$p"; exit; }
+    done
+# vi: ts=4 expandtab
diff --git a/tests/cloud_tests/testcases/modules/ntp_pools.yaml b/tests/cloud_tests/testcases/modules/ntp_pools.yaml
index d490b228..60fa0fd1 100644
--- a/tests/cloud_tests/testcases/modules/ntp_pools.yaml
+++ b/tests/cloud_tests/testcases/modules/ntp_pools.yaml
@@ -9,6 +9,7 @@ required_features:
 cloud_config: |
   #cloud-config
   ntp:
+    ntp_client: ntp
     pools:
         - 0.cloud-init.mypool
         - 1.cloud-init.mypool
diff --git a/tests/cloud_tests/testcases/modules/ntp_servers.yaml b/tests/cloud_tests/testcases/modules/ntp_servers.yaml
index 6b13b70e..ee636679 100644
--- a/tests/cloud_tests/testcases/modules/ntp_servers.yaml
+++ b/tests/cloud_tests/testcases/modules/ntp_servers.yaml
@@ -6,6 +6,7 @@ required_features:
 cloud_config: |
   #cloud-config
   ntp:
+    ntp_client: ntp
     servers:
         - 172.16.15.14
         - 172.16.17.18
diff --git a/tests/cloud_tests/testcases/modules/ntp_timesyncd.py b/tests/cloud_tests/testcases/modules/ntp_timesyncd.py
new file mode 100644
index 00000000..eca750bc
--- /dev/null
+++ b/tests/cloud_tests/testcases/modules/ntp_timesyncd.py
@@ -0,0 +1,15 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+"""cloud-init Integration Test Verify Script."""
+from tests.cloud_tests.testcases import base
+
+
+class TestNtpTimesyncd(base.CloudTestCase):
+    """Test ntp module with systemd-timesyncd client"""
+
+    def test_timesyncd_entries(self):
+        """Test timesyncd config entries"""
+        out = self.get_data_file('timesyncd_conf')
+        self.assertIn('.pool.ntp.org', out)
+
+# vi: ts=4 expandtab
diff --git a/tests/cloud_tests/testcases/modules/ntp_timesyncd.yaml b/tests/cloud_tests/testcases/modules/ntp_timesyncd.yaml
new file mode 100644
index 00000000..ee47a741
--- /dev/null
+++ b/tests/cloud_tests/testcases/modules/ntp_timesyncd.yaml
@@ -0,0 +1,15 @@
+#
+# ntp enabled, systemd-timesyncd selected, check conf file
+# as systemd-timesyncd won't start in a container
+#
+cloud_config: |
+  #cloud-config
+  ntp:
+    enabled: true
+    ntp_client: systemd-timesyncd
+collect_scripts:
+  timesyncd_conf: |
+    #!/bin/sh
+    cat /etc/systemd/timesyncd.conf.d/cloud-init.conf
+
+# vi: ts=4 expandtab
diff --git a/tests/unittests/test_distros/test_netconfig.py b/tests/unittests/test_distros/test_netconfig.py
index 1c2e45fe..7765e408 100644
--- a/tests/unittests/test_distros/test_netconfig.py
+++ b/tests/unittests/test_distros/test_netconfig.py
@@ -189,6 +189,12 @@ hn0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
         status: active
 """
 
+    def setUp(self):
+        super(TestNetCfgDistro, self).setUp()
+        self.add_patch('cloudinit.util.system_is_snappy', 'm_snappy')
+        self.add_patch('cloudinit.util.system_info', 'm_sysinfo')
+        self.m_sysinfo.return_value = {'dist': ('Distro', '99.1', 'Codename')}
+
     def _get_distro(self, dname, renderers=None):
         cls = distros.fetch(dname)
         cfg = settings.CFG_BUILTIN
diff --git a/tests/unittests/test_distros/test_user_data_normalize.py b/tests/unittests/test_distros/test_user_data_normalize.py
index 0fa9cdb5..fa4b6cfe 100644
--- a/tests/unittests/test_distros/test_user_data_normalize.py
+++ b/tests/unittests/test_distros/test_user_data_normalize.py
@@ -22,6 +22,12 @@ bcfg = {
 
 class TestUGNormalize(TestCase):
 
+    def setUp(self):
+        super(TestUGNormalize, self).setUp()
+        self.add_patch('cloudinit.util.system_is_snappy', 'm_snappy')
+        self.add_patch('cloudinit.util.system_info', 'm_sysinfo')
+        self.m_sysinfo.return_value = {'dist': ('Distro', '99.1', 'Codename')}
+
     def _make_distro(self, dtype, def_user=None):
         cfg = dict(settings.CFG_BUILTIN)
         cfg['system_info']['distro'] = dtype
diff --git a/tests/unittests/test_handler/test_handler_ntp.py b/tests/unittests/test_handler/test_handler_ntp.py
index 695897c0..1b3ca570 100644
--- a/tests/unittests/test_handler/test_handler_ntp.py
+++ b/tests/unittests/test_handler/test_handler_ntp.py
@@ -4,20 +4,21 @@ from cloudinit.config import cc_ntp
 from cloudinit.sources import DataSourceNone
 from cloudinit import (distros, helpers, cloud, util)
 from cloudinit.tests.helpers import (
-    FilesystemMockingTestCase, mock, skipUnlessJsonSchema)
+    CiTestCase, FilesystemMockingTestCase, mock, skipUnlessJsonSchema)
 
 
+import copy
 import os
 from os.path import dirname
 import shutil
 
-NTP_TEMPLATE = b"""\
+NTP_TEMPLATE = """\
 ## template: jinja
 servers {{servers}}
 pools {{pools}}
 """
 
-TIMESYNCD_TEMPLATE = b"""\
+TIMESYNCD_TEMPLATE = """\
 ## template:jinja
 [Time]
 {% if servers or pools -%}
@@ -32,56 +33,88 @@ class TestNtp(FilesystemMockingTestCase):
 
     def setUp(self):
         super(TestNtp, self).setUp()
-        self.subp = util.subp
         self.new_root = self.tmp_dir()
+        self.add_patch('cloudinit.util.system_is_snappy', 'm_snappy')
+        self.m_snappy.return_value = False
+        self.add_patch('cloudinit.util.system_info', 'm_sysinfo')
+        self.m_sysinfo.return_value = {'dist': ('Distro', '99.1', 'Codename')}
 
-    def _get_cloud(self, distro):
-        self.patchUtils(self.new_root)
+    def _get_cloud(self, distro, sys_cfg=None):
+        self.new_root = self.reRoot(root=self.new_root)
         paths = helpers.Paths({'templates_dir': self.new_root})
         cls = distros.fetch(distro)
-        mydist = cls(distro, {}, paths)
-        myds = DataSourceNone.DataSourceNone({}, mydist, paths)
-        return cloud.Cloud(myds, paths, {}, mydist, None)
+        if not sys_cfg:
+            sys_cfg = {}
+        mydist = cls(distro, sys_cfg, paths)
+        myds = DataSourceNone.DataSourceNone(sys_cfg, mydist, paths)
+        return cloud.Cloud(myds, paths, sys_cfg, mydist, None)
+
+    def _get_template_path(self, template_name, distro, basepath=None):
+        # ntp.conf.{distro} -> ntp.conf.debian.tmpl
+        template_fn = '{0}.tmpl'.format(
+            template_name.replace('{distro}', distro))
+        if not basepath:
+            basepath = self.new_root
+        path = os.path.join(basepath, template_fn)
+        return path
+
+    def _generate_template(self, template=None):
+        if not template:
+            template = NTP_TEMPLATE
+        confpath = os.path.join(self.new_root, 'client.conf')
+        template_fn = os.path.join(self.new_root, 'client.conf.tmpl')
+        util.write_file(template_fn, content=template)
+        return (confpath, template_fn)
+
+    def _mock_ntp_client_config(self, client=None, distro=None):
+        if not client:
+            client = 'ntp'
+        if not distro:
+            distro = 'ubuntu'
+        dcfg = cc_ntp.distro_ntp_client_configs(distro)
+        if client == 'systemd-timesyncd':
+            template = TIMESYNCD_TEMPLATE
+        else:
+            template = NTP_TEMPLATE
+        (confpath, template_fn) = self._generate_template(template=template)
+        ntpconfig = copy.deepcopy(dcfg[client])
+        ntpconfig['confpath'] = confpath
+        ntpconfig['template_name'] = os.path.basename(confpath)
+        return ntpconfig
 
     @mock.patch("cloudinit.config.cc_ntp.util")
     def test_ntp_install(self, mock_util):
-        """ntp_install installs via install_func when check_exe is absent."""
+        """ntp_install_client runs install_func when check_exe is absent."""
         mock_util.which.return_value = None  # check_exe not found.
         install_func = mock.MagicMock()
-        cc_ntp.install_ntp(install_func, packages=['ntpx'], check_exe='ntpdx')
-
+        cc_ntp.install_ntp_client(install_func,
+                                  packages=['ntpx'], check_exe='ntpdx')
         mock_util.which.assert_called_with('ntpdx')
         install_func.assert_called_once_with(['ntpx'])
 
     @mock.patch("cloudinit.config.cc_ntp.util")
     def test_ntp_install_not_needed(self, mock_util):
-        """ntp_install doesn't attempt install when check_exe is found."""
-        mock_util.which.return_value = ["/usr/sbin/ntpd"]  # check_exe found.
+        """ntp_install_client doesn't install when check_exe is found."""
+        client = 'chrony'
+        mock_util.which.return_value = [client]  # check_exe found.
         install_func = mock.MagicMock()
-        cc_ntp.install_ntp(install_func, packages=['ntp'], check_exe='ntpd')
+        cc_ntp.install_ntp_client(install_func, packages=[client],
+                                  check_exe=client)
         install_func.assert_not_called()
 
     @mock.patch("cloudinit.config.cc_ntp.util")
     def test_ntp_install_no_op_with_empty_pkg_list(self, mock_util):
-        """ntp_install calls install_func with empty list"""
+        """ntp_install_client runs install_func with empty list"""
         mock_util.which.return_value = None  # check_exe not found
         install_func = mock.MagicMock()
-        cc_ntp.install_ntp(install_func, packages=[], check_exe='timesyncd')
+        cc_ntp.install_ntp_client(install_func, packages=[],
+                                  check_exe='timesyncd')
         install_func.assert_called_once_with([])
 
-    def test_ntp_rename_ntp_conf(self):
-        """When NTP_CONF exists, rename_ntp moves it."""
-        ntpconf = self.tmp_path("ntp.conf", self.new_root)
-        util.write_file(ntpconf, "")
-        with mock.patch("cloudinit.config.cc_ntp.NTP_CONF", ntpconf):
-            cc_ntp.rename_ntp_conf()
-        self.assertFalse(os.path.exists(ntpconf))
-        self.assertTrue(os.path.exists("{0}.dist".format(ntpconf)))
-
     @mock.patch("cloudinit.config.cc_ntp.util")
     def test_reload_ntp_defaults(self, mock_util):
         """Test service is restarted/reloaded (defaults)"""
-        service = 'ntp'
+        service = 'ntp_service_name'
         cmd = ['service', service, 'restart']
         cc_ntp.reload_ntp(service)
         mock_util.subp.assert_called_with(cmd, capture=True)
@@ -89,193 +122,171 @@ class TestNtp(FilesystemMockingTestCase):
     @mock.patch("cloudinit.config.cc_ntp.util")
     def test_reload_ntp_systemd(self, mock_util):
         """Test service is restarted/reloaded (systemd)"""
-        service = 'ntp'
-        cmd = ['systemctl', 'reload-or-restart', service]
+        service = 'ntp_service_name'
         cc_ntp.reload_ntp(service, systemd=True)
-        mock_util.subp.assert_called_with(cmd, capture=True)
-
-    @mock.patch("cloudinit.config.cc_ntp.util")
-    def test_reload_ntp_systemd_timesycnd(self, mock_util):
-        """Test service is restarted/reloaded (systemd/timesyncd)"""
-        service = 'systemd-timesycnd'
         cmd = ['systemctl', 'reload-or-restart', service]
-        cc_ntp.reload_ntp(service, systemd=True)
         mock_util.subp.assert_called_with(cmd, capture=True)
 
+    def test_ntp_rename_ntp_conf(self):
+        """When NTP_CONF exists, rename_ntp moves it."""
+        ntpconf = self.tmp_path("ntp.conf", self.new_root)
+        util.write_file(ntpconf, "")
+        cc_ntp.rename_ntp_conf(confpath=ntpconf)
+        self.assertFalse(os.path.exists(ntpconf))
+        self.assertTrue(os.path.exists("{0}.dist".format(ntpconf)))
+
     def test_ntp_rename_ntp_conf_skip_missing(self):
         """When NTP_CONF doesn't exist rename_ntp doesn't create a file."""
         ntpconf = self.tmp_path("ntp.conf", self.new_root)
         self.assertFalse(os.path.exists(ntpconf))
-        with mock.patch("cloudinit.config.cc_ntp.NTP_CONF", ntpconf):
-            cc_ntp.rename_ntp_conf()
+        cc_ntp.rename_ntp_conf(confpath=ntpconf)
         self.assertFalse(os.path.exists("{0}.dist".format(ntpconf)))
         self.assertFalse(os.path.exists(ntpconf))
 
-    def test_write_ntp_config_template_from_ntp_conf_tmpl_with_servers(self):
-        """write_ntp_config_template reads content from ntp.conf.tmpl.
-
-        It reads ntp.conf.tmpl if present and renders the value from servers
-        key. When no pools key is defined, template is rendered using an empty
-        list for pools.
-        """
-        distro = 'ubuntu'
-        cfg = {
-            'servers': ['192.168.2.1', '192.168.2.2']
-        }
-        mycloud = self._get_cloud(distro)
-        ntp_conf = self.tmp_path("ntp.conf", self.new_root)  # Doesn't exist
-        # Create ntp.conf.tmpl
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.write_ntp_config_template(cfg, mycloud, ntp_conf)
-        content = util.read_file_or_url('file://' + ntp_conf).contents
+    def test_write_ntp_config_template_uses_ntp_conf_distro_no_servers(self):
+        """write_ntp_config_template reads from $client.conf.distro.tmpl"""
+        servers = []
+        pools = ['10.0.0.1', '10.0.0.2']
+        (confpath, template_fn) = self._generate_template()
+        mock_path = 'cloudinit.config.cc_ntp.temp_utils._TMPDIR'
+        with mock.patch(mock_path, self.new_root):
+            cc_ntp.write_ntp_config_template('ubuntu',
+                                             servers=servers, pools=pools,
+                                             path=confpath,
+                                             template_fn=template_fn,
+                                             template=None)
+        content = util.read_file_or_url('file://' + confpath).contents
         self.assertEqual(
-            "servers ['192.168.2.1', '192.168.2.2']\npools []\n",
-            content.decode())
+            "servers []\npools ['10.0.0.1', '10.0.0.2']\n", content.decode())
 
-    def test_write_ntp_config_template_uses_ntp_conf_distro_no_servers(self):
-        """write_ntp_config_template reads content from ntp.conf.distro.tmpl.
+    def test_write_ntp_config_template_defaults_pools_w_empty_lists(self):
+        """write_ntp_config_template defaults pools servers upon empty config.
 
-        It reads ntp.conf.<distro>.tmpl before attempting ntp.conf.tmpl. It
-        renders the value from the keys servers and pools. When no
-        servers value is present, template is rendered using an empty list.
+        When both pools and servers are empty, default NR_POOL_SERVERS get
+        configured.
         """
         distro = 'ubuntu'
-        cfg = {
-            'pools': ['10.0.0.1', '10.0.0.2']
-        }
-        mycloud = self._get_cloud(distro)
-        ntp_conf = self.tmp_path('ntp.conf', self.new_root)  # Doesn't exist
-        # Create ntp.conf.tmpl which isn't read
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(b'NOT READ: ntp.conf.<distro>.tmpl is primary')
-        # Create ntp.conf.tmpl.<distro>
-        with open('{0}.{1}.tmpl'.format(ntp_conf, distro), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.write_ntp_config_template(cfg, mycloud, ntp_conf)
-        content = util.read_file_or_url('file://' + ntp_conf).contents
+        pools = cc_ntp.generate_server_names(distro)
+        servers = []
+        (confpath, template_fn) = self._generate_template()
+        mock_path = 'cloudinit.config.cc_ntp.temp_utils._TMPDIR'
+        with mock.patch(mock_path, self.new_root):
+            cc_ntp.write_ntp_config_template(distro,
+                                             servers=servers, pools=pools,
+                                             path=confpath,
+                                             template_fn=template_fn,
+                                             template=None)
+        content = util.read_file_or_url('file://' + confpath).contents
         self.assertEqual(
-            "servers []\npools ['10.0.0.1', '10.0.0.2']\n",
+            "servers []\npools {0}\n".format(pools),
             content.decode())
 
-    def test_write_ntp_config_template_defaults_pools_when_empty_lists(self):
-        """write_ntp_config_template defaults pools servers upon empty config.
+    def test_defaults_pools_empty_lists_sles(self):
+        """write_ntp_config_template defaults opensuse pools upon empty config.
 
         When both pools and servers are empty, default NR_POOL_SERVERS get
         configured.
         """
-        distro = 'ubuntu'
-        mycloud = self._get_cloud(distro)
-        ntp_conf = self.tmp_path('ntp.conf', self.new_root)  # Doesn't exist
-        # Create ntp.conf.tmpl
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.write_ntp_config_template({}, mycloud, ntp_conf)
-        content = util.read_file_or_url('file://' + ntp_conf).contents
-        default_pools = [
-            "{0}.{1}.pool.ntp.org".format(x, distro)
-            for x in range(0, cc_ntp.NR_POOL_SERVERS)]
+        distro = 'sles'
+        default_pools = cc_ntp.generate_server_names(distro)
+        (confpath, template_fn) = self._generate_template()
+
+        cc_ntp.write_ntp_config_template(distro,
+                                         servers=[], pools=[],
+                                         path=confpath,
+                                         template_fn=template_fn,
+                                         template=None)
+        content = util.read_file_or_url('file://' + confpath).contents
+        for pool in default_pools:
+            self.assertIn('opensuse', pool)
         self.assertEqual(
-            "servers []\npools {0}\n".format(default_pools),
-            content.decode())
+            "servers []\npools {0}\n".format(default_pools), content.decode())
         self.assertIn(
             "Adding distro default ntp pool servers: {0}".format(
                 ",".join(default_pools)),
             self.logs.getvalue())
 
-    @mock.patch("cloudinit.config.cc_ntp.ntp_installable")
-    def test_ntp_handler_mocked_template(self, m_ntp_install):
-        """Test ntp handler renders ubuntu ntp.conf template."""
-        pools = ['0.mycompany.pool.ntp.org', '3.mycompany.pool.ntp.org']
-        servers = ['192.168.23.3', '192.168.23.4']
-        cfg = {
-            'ntp': {
-                'pools': pools,
-                'servers': servers
-            }
-        }
-        mycloud = self._get_cloud('ubuntu')
-        ntp_conf = self.tmp_path('ntp.conf', self.new_root)  # Doesn't exist
-        m_ntp_install.return_value = True
-
-        # Create ntp.conf.tmpl
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            with mock.patch.object(util, 'which', return_value=None):
-                cc_ntp.handle('notimportant', cfg, mycloud, None, None)
-
-        content = util.read_file_or_url('file://' + ntp_conf).contents
-        self.assertEqual(
-            'servers {0}\npools {1}\n'.format(servers, pools),
-            content.decode())
-
-    @mock.patch("cloudinit.config.cc_ntp.util")
-    def test_ntp_handler_mocked_template_snappy(self, m_util):
-        """Test ntp handler renders timesycnd.conf template on snappy."""
+    def test_timesyncd_template(self):
+        """Test timesycnd template is correct"""
         pools = ['0.mycompany.pool.ntp.org', '3.mycompany.pool.ntp.org']
         servers = ['192.168.23.3', '192.168.23.4']
-        cfg = {
-            'ntp': {
-                'pools': pools,
-                'servers': servers
-            }
-        }
-        mycloud = self._get_cloud('ubuntu')
-        m_util.system_is_snappy.return_value = True
-
-        # Create timesyncd.conf.tmpl
-        tsyncd_conf = self.tmp_path("timesyncd.conf", self.new_root)
-        template = '{0}.tmpl'.format(tsyncd_conf)
-        with open(template, 'wb') as stream:
-            stream.write(TIMESYNCD_TEMPLATE)
-
-        with mock.patch('cloudinit.config.cc_ntp.TIMESYNCD_CONF', tsyncd_conf):
-            cc_ntp.handle('notimportant', cfg, mycloud, None, None)
-
-        content = util.read_file_or_url('file://' + tsyncd_conf).contents
+        (confpath, template_fn) = self._generate_template(
+            template=TIMESYNCD_TEMPLATE)
+        cc_ntp.write_ntp_config_template('ubuntu',
+                                         servers=servers, pools=pools,
+                                         path=confpath,
+                                         template_fn=template_fn,
+                                         template=None)
+        content = util.read_file_or_url('file://' + confpath).contents
         self.assertEqual(
             "[Time]\nNTP=%s %s \n" % (" ".join(servers), " ".join(pools)),
             content.decode())
 
-    def test_ntp_handler_real_distro_templates(self):
-        """Test ntp handler renders the shipped distro ntp.conf templates."""
+    def test_distro_ntp_client_configs(self):
+        """Test we have updated ntp client configs on different distros"""
+        delta = copy.deepcopy(cc_ntp.DISTRO_CLIENT_CONFIG)
+        base = copy.deepcopy(cc_ntp.NTP_CLIENT_CONFIG)
+        # confirm no-delta distros match the base config
+        for distro in cc_ntp.distros:
+            if distro not in delta:
+                result = cc_ntp.distro_ntp_client_configs(distro)
+                self.assertEqual(base, result)
+        # for distros with delta, ensure the merged config values match
+        # what is set in the delta
+        for distro in delta.keys():
+            result = cc_ntp.distro_ntp_client_configs(distro)
+            for client in delta[distro].keys():
+                for key in delta[distro][client].keys():
+                    self.assertEqual(delta[distro][client][key],
+                                     result[client][key])
+
+    def test_ntp_handler_real_distro_ntp_templates(self):
+        """Test ntp handler renders the shipped distro ntp client templates."""
         pools = ['0.mycompany.pool.ntp.org', '3.mycompany.pool.ntp.org']
         servers = ['192.168.23.3', '192.168.23.4']
-        cfg = {
-            'ntp': {
-                'pools': pools,
-                'servers': servers
-            }
-        }
-        ntp_conf = self.tmp_path('ntp.conf', self.new_root)  # Doesn't exist
-        for distro in ('debian', 'ubuntu', 'fedora', 'rhel', 'sles'):
-            mycloud = self._get_cloud(distro)
-            root_dir = dirname(dirname(os.path.realpath(util.__file__)))
-            tmpl_file = os.path.join(
-                '{0}/templates/ntp.conf.{1}.tmpl'.format(root_dir, distro))
-            # Create a copy in our tmp_dir
-            shutil.copy(
-                tmpl_file,
-                os.path.join(self.new_root, 'ntp.conf.%s.tmpl' % distro))
-            with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-                with mock.patch.object(util, 'which', return_value=[True]):
-                    cc_ntp.handle('notimportant', cfg, mycloud, None, None)
-
-            content = util.read_file_or_url('file://' + ntp_conf).contents
-            expected_servers = '\n'.join([
-                'server {0} iburst'.format(server) for server in servers])
-            self.assertIn(
-                expected_servers, content.decode(),
-                'failed to render ntp.conf for distro:{0}'.format(distro))
-            expected_pools = '\n'.join([
-                'pool {0} iburst'.format(pool) for pool in pools])
-            self.assertIn(
-                expected_pools, content.decode(),
-                'failed to render ntp.conf for distro:{0}'.format(distro))
+        for client in ['ntp', 'systemd-timesyncd', 'chrony']:
+            for distro in cc_ntp.distros:
+                distro_cfg = cc_ntp.distro_ntp_client_configs(distro)
+                ntpclient = distro_cfg[client]
+                confpath = (
+                    os.path.join(self.new_root, ntpclient.get('confpath')[1:]))
+                template = ntpclient.get('template_name')
+                # find sourcetree template file
+                root_dir = (
+                    dirname(dirname(os.path.realpath(util.__file__))) +
+                    '/templates')
+                source_fn = self._get_template_path(template, distro,
+                                                    basepath=root_dir)
+                template_fn = self._get_template_path(template, distro)
+                # don't fail if cloud-init doesn't have a template for
+                # a distro,client pair
+                if not os.path.exists(source_fn):
+                    continue
+                # Create a copy in our tmp_dir
+                shutil.copy(source_fn, template_fn)
+                cc_ntp.write_ntp_config_template(distro, servers=servers,
+                                                 pools=pools, path=confpath,
+                                                 template_fn=template_fn)
+                content = util.read_file_or_url('file://' + confpath).contents
+                if client in ['ntp', 'chrony']:
+                    expected_servers = '\n'.join([
+                        'server {0} iburst'.format(srv) for srv in servers])
+                    print('distro=%s client=%s' % (distro, client))
+                    self.assertIn(expected_servers, content.decode(),
+                                  ('failed to render {0} conf'
+                                   ' for distro:{1}'.format(client, distro)))
+                    expected_pools = '\n'.join([
+                        'pool {0} iburst'.format(pool) for pool in pools])
+                    self.assertIn(expected_pools, content.decode(),
+                                  ('failed to render {0} conf'
+                                   ' for distro:{1}'.format(client, distro)))
+                elif client == 'systemd-timesyncd':
+                    expected_content = (
+                        "# cloud-init generated file\n" +
+                        "# See timesyncd.conf(5) for details.\n\n" +
+                        "[Time]\nNTP=%s %s \n" % (" ".join(servers),
+                                                  " ".join(pools)))
+                    self.assertEqual(expected_content, content.decode())
 
     def test_no_ntpcfg_does_nothing(self):
         """When no ntp section is defined handler logs a warning and noops."""
@@ -285,95 +296,99 @@ class TestNtp(FilesystemMockingTestCase):
             'not present or disabled by cfg\n',
             self.logs.getvalue())
 
-    def test_ntp_handler_schema_validation_allows_empty_ntp_config(self):
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_schema_validation_allows_empty_ntp_config(self,
+                                                                   m_select):
         """Ntp schema validation allows for an empty ntp: configuration."""
         valid_empty_configs = [{'ntp': {}}, {'ntp': None}]
-        distro = 'ubuntu'
-        cc = self._get_cloud(distro)
-        ntp_conf = os.path.join(self.new_root, 'ntp.conf')
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
         for valid_empty_config in valid_empty_configs:
-            with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-                cc_ntp.handle('cc_ntp', valid_empty_config, cc, None, [])
-            with open(ntp_conf) as stream:
-                content = stream.read()
-            default_pools = [
-                "{0}.{1}.pool.ntp.org".format(x, distro)
-                for x in range(0, cc_ntp.NR_POOL_SERVERS)]
-            self.assertEqual(
-                "servers []\npools {0}\n".format(default_pools),
-                content)
-        self.assertNotIn('Invalid config:', self.logs.getvalue())
+            for distro in cc_ntp.distros:
+                mycloud = self._get_cloud(distro)
+                ntpconfig = self._mock_ntp_client_config(distro=distro)
+                confpath = ntpconfig['confpath']
+                m_select.return_value = ntpconfig
+                cc_ntp.handle('cc_ntp', valid_empty_config, mycloud, None, [])
+                content = util.read_file_or_url('file://' + confpath).contents
+                pools = cc_ntp.generate_server_names(mycloud.distro.name)
+                self.assertEqual(
+                    "servers []\npools {0}\n".format(pools), content.decode())
+            self.assertNotIn('Invalid config:', self.logs.getvalue())
 
     @skipUnlessJsonSchema()
-    def test_ntp_handler_schema_validation_warns_non_string_item_type(self):
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_schema_validation_warns_non_string_item_type(self,
+                                                                      m_sel):
         """Ntp schema validation warns of non-strings in pools or servers.
 
         Schema validation is not strict, so ntp config is still be rendered.
         """
         invalid_config = {'ntp': {'pools': [123], 'servers': ['valid', None]}}
-        cc = self._get_cloud('ubuntu')
-        ntp_conf = os.path.join(self.new_root, 'ntp.conf')
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.handle('cc_ntp', invalid_config, cc, None, [])
-        self.assertIn(
-            "Invalid config:\nntp.pools.0: 123 is not of type 'string'\n"
-            "ntp.servers.1: None is not of type 'string'",
-            self.logs.getvalue())
-        with open(ntp_conf) as stream:
-            content = stream.read()
-        self.assertEqual("servers ['valid', None]\npools [123]\n", content)
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(distro=distro)
+            confpath = ntpconfig['confpath']
+            m_sel.return_value = ntpconfig
+            cc_ntp.handle('cc_ntp', invalid_config, mycloud, None, [])
+            self.assertIn(
+                "Invalid config:\nntp.pools.0: 123 is not of type 'string'\n"
+                "ntp.servers.1: None is not of type 'string'",
+                self.logs.getvalue())
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual("servers ['valid', None]\npools [123]\n",
+                             content.decode())
 
     @skipUnlessJsonSchema()
-    def test_ntp_handler_schema_validation_warns_of_non_array_type(self):
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_schema_validation_warns_of_non_array_type(self,
+                                                                   m_select):
         """Ntp schema validation warns of non-array pools or servers types.
 
         Schema validation is not strict, so ntp config is still be rendered.
         """
         invalid_config = {'ntp': {'pools': 123, 'servers': 'non-array'}}
-        cc = self._get_cloud('ubuntu')
-        ntp_conf = os.path.join(self.new_root, 'ntp.conf')
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.handle('cc_ntp', invalid_config, cc, None, [])
-        self.assertIn(
-            "Invalid config:\nntp.pools: 123 is not of type 'array'\n"
-            "ntp.servers: 'non-array' is not of type 'array'",
-            self.logs.getvalue())
-        with open(ntp_conf) as stream:
-            content = stream.read()
-        self.assertEqual("servers non-array\npools 123\n", content)
+
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(distro=distro)
+            confpath = ntpconfig['confpath']
+            m_select.return_value = ntpconfig
+            cc_ntp.handle('cc_ntp', invalid_config, mycloud, None, [])
+            self.assertIn(
+                "Invalid config:\nntp.pools: 123 is not of type 'array'\n"
+                "ntp.servers: 'non-array' is not of type 'array'",
+                self.logs.getvalue())
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual("servers non-array\npools 123\n",
+                             content.decode())
 
     @skipUnlessJsonSchema()
-    def test_ntp_handler_schema_validation_warns_invalid_key_present(self):
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_schema_validation_warns_invalid_key_present(self,
+                                                                     m_select):
         """Ntp schema validation warns of invalid keys present in ntp config.
 
         Schema validation is not strict, so ntp config is still be rendered.
         """
         invalid_config = {
             'ntp': {'invalidkey': 1, 'pools': ['0.mycompany.pool.ntp.org']}}
-        cc = self._get_cloud('ubuntu')
-        ntp_conf = os.path.join(self.new_root, 'ntp.conf')
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.handle('cc_ntp', invalid_config, cc, None, [])
-        self.assertIn(
-            "Invalid config:\nntp: Additional properties are not allowed "
-            "('invalidkey' was unexpected)",
-            self.logs.getvalue())
-        with open(ntp_conf) as stream:
-            content = stream.read()
-        self.assertEqual(
-            "servers []\npools ['0.mycompany.pool.ntp.org']\n",
-            content)
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(distro=distro)
+            confpath = ntpconfig['confpath']
+            m_select.return_value = ntpconfig
+            cc_ntp.handle('cc_ntp', invalid_config, mycloud, None, [])
+            self.assertIn(
+                "Invalid config:\nntp: Additional properties are not allowed "
+                "('invalidkey' was unexpected)",
+                self.logs.getvalue())
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual(
+                "servers []\npools ['0.mycompany.pool.ntp.org']\n",
+                content.decode())
 
     @skipUnlessJsonSchema()
-    def test_ntp_handler_schema_validation_warns_of_duplicates(self):
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_schema_validation_warns_of_duplicates(self, m_select):
         """Ntp schema validation warns of duplicates in servers or pools.
 
         Schema validation is not strict, so ntp config is still be rendered.
@@ -381,74 +396,334 @@ class TestNtp(FilesystemMockingTestCase):
         invalid_config = {
             'ntp': {'pools': ['0.mypool.org', '0.mypool.org'],
                     'servers': ['10.0.0.1', '10.0.0.1']}}
-        cc = self._get_cloud('ubuntu')
-        ntp_conf = os.path.join(self.new_root, 'ntp.conf')
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.handle('cc_ntp', invalid_config, cc, None, [])
-        self.assertIn(
-            "Invalid config:\nntp.pools: ['0.mypool.org', '0.mypool.org'] has "
-            "non-unique elements\nntp.servers: ['10.0.0.1', '10.0.0.1'] has "
-            "non-unique elements",
-            self.logs.getvalue())
-        with open(ntp_conf) as stream:
-            content = stream.read()
-        self.assertEqual(
-            "servers ['10.0.0.1', '10.0.0.1']\n"
-            "pools ['0.mypool.org', '0.mypool.org']\n",
-            content)
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(distro=distro)
+            confpath = ntpconfig['confpath']
+            m_select.return_value = ntpconfig
+            cc_ntp.handle('cc_ntp', invalid_config, mycloud, None, [])
+            self.assertIn(
+                "Invalid config:\nntp.pools: ['0.mypool.org', '0.mypool.org']"
+                " has non-unique elements\nntp.servers: "
+                "['10.0.0.1', '10.0.0.1'] has non-unique elements",
+                self.logs.getvalue())
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual(
+                "servers ['10.0.0.1', '10.0.0.1']\n"
+                "pools ['0.mypool.org', '0.mypool.org']\n", content.decode())
 
-    @mock.patch("cloudinit.config.cc_ntp.ntp_installable")
-    def test_ntp_handler_timesyncd(self, m_ntp_install):
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_timesyncd(self, m_select):
         """Test ntp handler configures timesyncd"""
-        m_ntp_install.return_value = False
-        distro = 'ubuntu'
-        cfg = {
-            'servers': ['192.168.2.1', '192.168.2.2'],
-            'pools': ['0.mypool.org'],
-        }
-        mycloud = self._get_cloud(distro)
-        tsyncd_conf = self.tmp_path("timesyncd.conf", self.new_root)
-        # Create timesyncd.conf.tmpl
-        template = '{0}.tmpl'.format(tsyncd_conf)
-        print(template)
-        with open(template, 'wb') as stream:
-            stream.write(TIMESYNCD_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.TIMESYNCD_CONF', tsyncd_conf):
-            cc_ntp.write_ntp_config_template(cfg, mycloud, tsyncd_conf,
-                                             template='timesyncd.conf')
-
-        content = util.read_file_or_url('file://' + tsyncd_conf).contents
-        self.assertEqual(
-            "[Time]\nNTP=192.168.2.1 192.168.2.2 0.mypool.org \n",
-            content.decode())
+        servers = ['192.168.2.1', '192.168.2.2']
+        pools = ['0.mypool.org']
+        cfg = {'ntp': {'servers': servers, 'pools': pools}}
+        client = 'systemd-timesyncd'
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(distro=distro,
+                                                     client=client)
+            confpath = ntpconfig['confpath']
+            m_select.return_value = ntpconfig
+            cc_ntp.handle('cc_ntp', cfg, mycloud, None, [])
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual(
+                "[Time]\nNTP=192.168.2.1 192.168.2.2 0.mypool.org \n",
+                content.decode())
+
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_handler_enabled_false(self, m_select):
+        """Test ntp handler does not run if enabled: false """
+        cfg = {'ntp': {'enabled': False}}
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            cc_ntp.handle('notimportant', cfg, mycloud, None, None)
+            self.assertEqual(0, m_select.call_count)
+
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    @mock.patch("cloudinit.distros.Distro.uses_systemd")
+    def test_ntp_the_whole_package(self, m_sysd, m_select):
+        """Test enabled config renders template, and restarts service """
+        cfg = {'ntp': {'enabled': True}}
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(distro=distro)
+            confpath = ntpconfig['confpath']
+            service_name = ntpconfig['service_name']
+            m_select.return_value = ntpconfig
+            pools = cc_ntp.generate_server_names(mycloud.distro.name)
+            # force uses systemd path
+            m_sysd.return_value = True
+            with mock.patch('cloudinit.config.cc_ntp.util') as m_util:
+                # allow use of util.mergemanydict
+                m_util.mergemanydict.side_effect = util.mergemanydict
+                # default client is present
+                m_util.which.return_value = True
+                # use the config 'enabled' value
+                m_util.is_false.return_value = util.is_false(
+                    cfg['ntp']['enabled'])
+                cc_ntp.handle('notimportant', cfg, mycloud, None, None)
+                m_util.subp.assert_called_with(
+                    ['systemctl', 'reload-or-restart',
+                     service_name], capture=True)
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual(
+                "servers []\npools {0}\n".format(pools),
+                content.decode())
+
+    def test_opensuse_picks_chrony(self):
+        """Test opensuse picks chrony or ntp on certain distro versions"""
+        #  < 15.0  => ntp
+        self.m_sysinfo.return_value = {'dist':
+                                       ('openSUSE', '13.2', 'Harlequin')}
+        mycloud = self._get_cloud('opensuse')
+        expected_client = mycloud.distro.preferred_ntp_clients[0]
+        self.assertEqual('ntp', expected_client)
+
+        #  >= 15.0 and  not openSUSE => chrony
+        self.m_sysinfo.return_value = {'dist':
+                                       ('SLES', '15.0',
+                                        'SUSE Linux Enterprise Server 15')}
+        mycloud = self._get_cloud('sles')
+        expected_client = mycloud.distro.preferred_ntp_clients[0]
+        self.assertEqual('chrony', expected_client)
+
+        #  >= 15.0 and  openSUSE and ver != 42  => chrony
+        self.m_sysinfo.return_value = {'dist': ('openSUSE Tumbleweed',
+                                                '20180326',
+                                                'timbleweed')}
+        mycloud = self._get_cloud('opensuse')
+        expected_client = mycloud.distro.preferred_ntp_clients[0]
+        self.assertEqual('chrony', expected_client)
+
+    def test_ubuntu_xenial_picks_ntp(self):
+        """Test Ubuntu picks ntp on xenial release"""
+
+        self.m_sysinfo.return_value = {'dist': ('Ubuntu', '16.04', 'xenial')}
+        mycloud = self._get_cloud('ubuntu')
+        expected_client = mycloud.distro.preferred_ntp_clients[0]
+        self.assertEqual('ntp', expected_client)
 
-    def test_write_ntp_config_template_defaults_pools_empty_lists_sles(self):
-        """write_ntp_config_template defaults pools servers upon empty config.
+    @mock.patch('cloudinit.config.cc_ntp.util.which')
+    def test_snappy_system_picks_timesyncd(self, m_which):
+        """Test snappy systems prefer installed clients"""
 
-        When both pools and servers are empty, default NR_POOL_SERVERS get
-        configured.
-        """
-        distro = 'sles'
-        mycloud = self._get_cloud(distro)
-        ntp_conf = self.tmp_path('ntp.conf', self.new_root)  # Doesn't exist
-        # Create ntp.conf.tmpl
-        with open('{0}.tmpl'.format(ntp_conf), 'wb') as stream:
-            stream.write(NTP_TEMPLATE)
-        with mock.patch('cloudinit.config.cc_ntp.NTP_CONF', ntp_conf):
-            cc_ntp.write_ntp_config_template({}, mycloud, ntp_conf)
-        content = util.read_file_or_url('file://' + ntp_conf).contents
-        default_pools = [
-            "{0}.opensuse.pool.ntp.org".format(x)
-            for x in range(0, cc_ntp.NR_POOL_SERVERS)]
-        self.assertEqual(
-            "servers []\npools {0}\n".format(default_pools),
-            content.decode())
-        self.assertIn(
-            "Adding distro default ntp pool servers: {0}".format(
-                ",".join(default_pools)),
-            self.logs.getvalue())
+        # we are on ubuntu-core here
+        self.m_snappy.return_value = True
 
+        # ubuntu core systems will have timesyncd installed
+        m_which.side_effect = iter([None, '/lib/systemd/systemd-timesyncd',
+                                    None, None, None])
+        distro = 'ubuntu'
+        mycloud = self._get_cloud(distro)
+        distro_configs = cc_ntp.distro_ntp_client_configs(distro)
+        expected_client = 'systemd-timesyncd'
+        expected_cfg = distro_configs[expected_client]
+        expected_calls = []
+        # we only get to timesyncd
+        for client in mycloud.distro.preferred_ntp_clients[0:2]:
+            cfg = distro_configs[client]
+            expected_calls.append(mock.call(cfg['check_exe']))
+        result = cc_ntp.select_ntp_client(None, mycloud.distro)
+        m_which.assert_has_calls(expected_calls)
+        self.assertEqual(sorted(expected_cfg), sorted(cfg))
+        self.assertEqual(sorted(expected_cfg), sorted(result))
+
+    @mock.patch('cloudinit.config.cc_ntp.util.which')
+    def test_ntp_distro_searches_all_preferred_clients(self, m_which):
+        """Test select_ntp_client search all distro perferred clients """
+        # nothing is installed
+        m_which.return_value = None
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            distro_configs = cc_ntp.distro_ntp_client_configs(distro)
+            expected_client = mycloud.distro.preferred_ntp_clients[0]
+            expected_cfg = distro_configs[expected_client]
+            expected_calls = []
+            for client in mycloud.distro.preferred_ntp_clients:
+                cfg = distro_configs[client]
+                expected_calls.append(mock.call(cfg['check_exe']))
+            cc_ntp.select_ntp_client({}, mycloud.distro)
+            m_which.assert_has_calls(expected_calls)
+            self.assertEqual(sorted(expected_cfg), sorted(cfg))
+
+    @mock.patch('cloudinit.config.cc_ntp.util.which')
+    def test_user_cfg_ntp_client_auto_uses_distro_clients(self, m_which):
+        """Test user_cfg.ntp_client='auto' defaults to distro search"""
+        # nothing is installed
+        m_which.return_value = None
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            distro_configs = cc_ntp.distro_ntp_client_configs(distro)
+            expected_client = mycloud.distro.preferred_ntp_clients[0]
+            expected_cfg = distro_configs[expected_client]
+            expected_calls = []
+            for client in mycloud.distro.preferred_ntp_clients:
+                cfg = distro_configs[client]
+                expected_calls.append(mock.call(cfg['check_exe']))
+            cc_ntp.select_ntp_client('auto', mycloud.distro)
+            m_which.assert_has_calls(expected_calls)
+            self.assertEqual(sorted(expected_cfg), sorted(cfg))
+
+    @mock.patch('cloudinit.config.cc_ntp.write_ntp_config_template')
+    @mock.patch('cloudinit.cloud.Cloud.get_template_filename')
+    @mock.patch('cloudinit.config.cc_ntp.util.which')
+    def test_ntp_custom_client_overrides_installed_clients(self, m_which,
+                                                           m_tmpfn, m_write):
+        """Test user client is installed despite other clients present """
+        client = 'ntpdate'
+        cfg = {'ntp': {'ntp_client': client}}
+        for distro in cc_ntp.distros:
+            # client is not installed
+            m_which.side_effect = iter([None])
+            mycloud = self._get_cloud(distro)
+            with mock.patch.object(mycloud.distro,
+                                   'install_packages') as m_install:
+                cc_ntp.handle('notimportant', cfg, mycloud, None, None)
+            m_install.assert_called_with([client])
+            m_which.assert_called_with(client)
+
+    @mock.patch('cloudinit.config.cc_ntp.util.which')
+    def test_ntp_system_config_overrides_distro_builtin_clients(self, m_which):
+        """Test distro system_config overrides builtin preferred ntp clients"""
+        system_client = 'chrony'
+        sys_cfg = {'ntp_client': system_client}
+        # no clients installed
+        m_which.return_value = None
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro, sys_cfg=sys_cfg)
+            distro_configs = cc_ntp.distro_ntp_client_configs(distro)
+            expected_cfg = distro_configs[system_client]
+            result = cc_ntp.select_ntp_client(None, mycloud.distro)
+            self.assertEqual(sorted(expected_cfg), sorted(result))
+            m_which.assert_has_calls([])
+
+    @mock.patch('cloudinit.config.cc_ntp.util.which')
+    def test_ntp_user_config_overrides_system_cfg(self, m_which):
+        """Test user-data overrides system_config ntp_client"""
+        system_client = 'chrony'
+        sys_cfg = {'ntp_client': system_client}
+        user_client = 'systemd-timesyncd'
+        # no clients installed
+        m_which.return_value = None
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro, sys_cfg=sys_cfg)
+            distro_configs = cc_ntp.distro_ntp_client_configs(distro)
+            expected_cfg = distro_configs[user_client]
+            result = cc_ntp.select_ntp_client(user_client, mycloud.distro)
+            self.assertEqual(sorted(expected_cfg), sorted(result))
+            m_which.assert_has_calls([])
+
+    @mock.patch('cloudinit.config.cc_ntp.reload_ntp')
+    @mock.patch('cloudinit.config.cc_ntp.install_ntp_client')
+    def test_ntp_user_provided_config_with_template(self, m_install, m_reload):
+        custom = r'\n#MyCustomTemplate'
+        user_template = NTP_TEMPLATE + custom
+        confpath = os.path.join(self.new_root, 'etc/myntp/myntp.conf')
+        cfg = {
+            'ntp': {
+                'pools': ['mypool.org'],
+                'ntp_client': 'myntpd',
+                'config': {
+                    'check_exe': 'myntpd',
+                    'confpath': confpath,
+                    'packages': ['myntp'],
+                    'service_name': 'myntp',
+                    'template': user_template,
+                }
+            }
+        }
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            mock_path = 'cloudinit.config.cc_ntp.temp_utils._TMPDIR'
+            with mock.patch(mock_path, self.new_root):
+                cc_ntp.handle('notimportant', cfg, mycloud, None, None)
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual(
+                "servers []\npools ['mypool.org']\n%s" % custom,
+                content.decode())
+
+    @mock.patch('cloudinit.config.cc_ntp.supplemental_schema_validation')
+    @mock.patch('cloudinit.config.cc_ntp.reload_ntp')
+    @mock.patch('cloudinit.config.cc_ntp.install_ntp_client')
+    @mock.patch('cloudinit.config.cc_ntp.select_ntp_client')
+    def test_ntp_user_provided_config_template_only(self, m_select, m_install,
+                                                    m_reload, m_schema):
+        """Test custom template for default client"""
+        custom = r'\n#MyCustomTemplate'
+        user_template = NTP_TEMPLATE + custom
+        client = 'chrony'
+        cfg = {
+            'pools': ['mypool.org'],
+            'ntp_client': client,
+            'config': {
+                'template': user_template,
+            }
+        }
+        expected_merged_cfg = {
+            'check_exe': 'chronyd',
+            'confpath': '{tmpdir}/client.conf'.format(tmpdir=self.new_root),
+            'template_name': 'client.conf', 'template': user_template,
+            'service_name': 'chrony', 'packages': ['chrony']}
+        for distro in cc_ntp.distros:
+            mycloud = self._get_cloud(distro)
+            ntpconfig = self._mock_ntp_client_config(client=client,
+                                                     distro=distro)
+            confpath = ntpconfig['confpath']
+            m_select.return_value = ntpconfig
+            mock_path = 'cloudinit.config.cc_ntp.temp_utils._TMPDIR'
+            with mock.patch(mock_path, self.new_root):
+                cc_ntp.handle('notimportant',
+                              {'ntp': cfg}, mycloud, None, None)
+            content = util.read_file_or_url('file://' + confpath).contents
+            self.assertEqual(
+                "servers []\npools ['mypool.org']\n%s" % custom,
+                content.decode())
+        m_schema.assert_called_with(expected_merged_cfg)
+
+
+class TestSupplementalSchemaValidation(CiTestCase):
+
+    def test_error_on_missing_keys(self):
+        """ValueError raised reporting any missing required ntp:config keys"""
+        cfg = {}
+        match = (r'Invalid ntp configuration:\\nMissing required ntp:config'
+                 ' keys: check_exe, confpath, packages, service_name')
+        with self.assertRaisesRegex(ValueError, match):
+            cc_ntp.supplemental_schema_validation(cfg)
+
+    def test_error_requiring_either_template_or_template_name(self):
+        """ValueError raised if both template not template_name are None."""
+        cfg = {'confpath': 'someconf', 'check_exe': '', 'service_name': '',
+               'template': None, 'template_name': None, 'packages': []}
+        match = (r'Invalid ntp configuration:\\nEither ntp:config:template'
+                 ' or ntp:config:template_name values are required')
+        with self.assertRaisesRegex(ValueError, match):
+            cc_ntp.supplemental_schema_validation(cfg)
+
+    def test_error_on_non_list_values(self):
+        """ValueError raised when packages is not of type list."""
+        cfg = {'confpath': 'someconf', 'check_exe': '', 'service_name': '',
+               'template': 'asdf', 'template_name': None, 'packages': 'NOPE'}
+        match = (r'Invalid ntp configuration:\\nExpected a list of required'
+                 ' package names for ntp:config:packages. Found \(NOPE\)')
+        with self.assertRaisesRegex(ValueError, match):
+            cc_ntp.supplemental_schema_validation(cfg)
+
+    def test_error_on_non_string_values(self):
+        """ValueError raised for any values expected as string type."""
+        cfg = {'confpath': 1, 'check_exe': 2, 'service_name': 3,
+               'template': 4, 'template_name': 5, 'packages': []}
+        errors = [
+            'Expected a config file path ntp:config:confpath. Found (1)',
+            'Expected a string type for ntp:config:check_exe. Found (2)',
+            'Expected a string type for ntp:config:service_name. Found (3)',
+            'Expected a string type for ntp:config:template. Found (4)',
+            'Expected a string type for ntp:config:template_name. Found (5)']
+        with self.assertRaises(ValueError) as context_mgr:
+            cc_ntp.supplemental_schema_validation(cfg)
+        error_msg = str(context_mgr.exception)
+        for error in errors:
+            self.assertIn(error, error_msg)
 
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