Merge ~james-page/ntp-charm:add-update-status into ntp-charm:master

[James Page]

[Stuart Bishop (stub)]

This looks familiar...

Again, mostly charmhelpers sync and the new hook looks good.

Someone needs to land this on the git branch since I'm not here.

review: Approve

[Paul Gear (paulgear)]

Merged; one question about future work (when/if we rewrite this as a reactive charm), it is common practice to use hookenv.status_set('blocked', ...) to indicate what the reactive states are waiting on during deployment. This patch prevents that. Would you be comfortable with assess_status() being called only after the charm is fully installed, and during the update-status hook?

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ba077a4
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+bin
diff --git a/charm-helpers-sync.yaml b/charm-helpers-sync.yaml
index a1cbbae..6d2e9d2 100644
--- a/charm-helpers-sync.yaml
+++ b/charm-helpers-sync.yaml
@@ -1,6 +1,7 @@
 branch: lp:charm-helpers
 destination: hooks/charmhelpers
 include:
+    - osplatform
     - core
     - fetch
     - contrib.templating.jinja
diff --git a/hooks/charmhelpers/__init__.py b/hooks/charmhelpers/__init__.py
index f72e7f8..4886788 100644
--- a/hooks/charmhelpers/__init__.py
+++ b/hooks/charmhelpers/__init__.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 # Bootstrap charm-helpers, installing its dependencies if necessary using
 # only standard libraries.
diff --git a/hooks/charmhelpers/contrib/__init__.py b/hooks/charmhelpers/contrib/__init__.py
index d1400a0..d7567b8 100644
--- a/hooks/charmhelpers/contrib/__init__.py
+++ b/hooks/charmhelpers/contrib/__init__.py
@@ -1,15 +1,13 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/hooks/charmhelpers/contrib/charmsupport/__init__.py b/hooks/charmhelpers/contrib/charmsupport/__init__.py
index d1400a0..d7567b8 100644
--- a/hooks/charmhelpers/contrib/charmsupport/__init__.py
+++ b/hooks/charmhelpers/contrib/charmsupport/__init__.py
@@ -1,15 +1,13 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/hooks/charmhelpers/contrib/charmsupport/nrpe.py b/hooks/charmhelpers/contrib/charmsupport/nrpe.py
index 65b1a27..1410512 100644
--- a/hooks/charmhelpers/contrib/charmsupport/nrpe.py
+++ b/hooks/charmhelpers/contrib/charmsupport/nrpe.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 """Compatibility with the nrpe-external-master charm"""
 # Copyright 2012 Canonical Ltd.
@@ -40,6 +38,7 @@ from charmhelpers.core.hookenv import (
 )
 
 from charmhelpers.core.host import service
+from charmhelpers.core import host
 
 # This module adds compatibility with the nrpe-external-master and plain nrpe
 # subordinate charms. To use it in your charm:
@@ -110,6 +109,13 @@ from charmhelpers.core.host import service
 #    def local_monitors_relation_changed():
 #        update_nrpe_config()
 #
+# 4.a If your charm is a subordinate charm set primary=False
+#
+#    from charmsupport.nrpe import NRPE
+#    (...)
+#    def update_nrpe_config():
+#        nrpe_compat = NRPE(primary=False)
+#
 # 5. ln -s hooks.py nrpe-external-master-relation-changed
 #    ln -s hooks.py local-monitors-relation-changed
 
@@ -222,9 +228,10 @@ class NRPE(object):
     nagios_exportdir = '/var/lib/nagios/export'
     nrpe_confdir = '/etc/nagios/nrpe.d'
 
-    def __init__(self, hostname=None):
+    def __init__(self, hostname=None, primary=True):
         super(NRPE, self).__init__()
         self.config = config()
+        self.primary = primary
         self.nagios_context = self.config['nagios_context']
         if 'nagios_servicegroups' in self.config and self.config['nagios_servicegroups']:
             self.nagios_servicegroups = self.config['nagios_servicegroups']
@@ -240,6 +247,12 @@ class NRPE(object):
             else:
                 self.hostname = "{}-{}".format(self.nagios_context, self.unit_name)
         self.checks = []
+        # Iff in an nrpe-external-master relation hook, set primary status
+        relation = relation_ids('nrpe-external-master')
+        if relation:
+            log("Setting charm primary status {}".format(primary))
+            for rid in relation_ids('nrpe-external-master'):
+                relation_set(relation_id=rid, relation_settings={'primary': self.primary})
 
     def add_check(self, *args, **kwargs):
         self.checks.append(Check(*args, **kwargs))
@@ -296,7 +309,7 @@ def get_nagios_hostcontext(relation_name='nrpe-external-master'):
     :param str relation_name: Name of relation nrpe sub joined to
     """
     for rel in relations_of_type(relation_name):
-        if 'nagios_hostname' in rel:
+        if 'nagios_host_context' in rel:
             return rel['nagios_host_context']
 
 
@@ -334,9 +347,20 @@ def add_init_service_checks(nrpe, services, unit_name):
     :param str unit_name: Unit name to use in check description
     """
     for svc in services:
+        # Don't add a check for these services from neutron-gateway
+        if svc in ['ext-port', 'os-charm-phy-nic-mtu']:
+            next
+
         upstart_init = '/etc/init/%s.conf' % svc
         sysv_init = '/etc/init.d/%s' % svc
-        if os.path.exists(upstart_init):
+
+        if host.init_is_systemd():
+            nrpe.add_check(
+                shortname=svc,
+                description='process check {%s}' % unit_name,
+                check_cmd='check_systemd.py %s' % svc
+            )
+        elif os.path.exists(upstart_init):
             nrpe.add_check(
                 shortname=svc,
                 description='process check {%s}' % unit_name,
diff --git a/hooks/charmhelpers/contrib/charmsupport/volumes.py b/hooks/charmhelpers/contrib/charmsupport/volumes.py
index 320961b..7ea43f0 100644
--- a/hooks/charmhelpers/contrib/charmsupport/volumes.py
+++ b/hooks/charmhelpers/contrib/charmsupport/volumes.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 '''
 Functions for managing volumes in juju units. One volume is supported per unit.
diff --git a/hooks/charmhelpers/contrib/templating/__init__.py b/hooks/charmhelpers/contrib/templating/__init__.py
index d1400a0..d7567b8 100644
--- a/hooks/charmhelpers/contrib/templating/__init__.py
+++ b/hooks/charmhelpers/contrib/templating/__init__.py
@@ -1,15 +1,13 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/hooks/charmhelpers/contrib/templating/jinja.py b/hooks/charmhelpers/contrib/templating/jinja.py
index c5efb16..38d4fba 100644
--- a/hooks/charmhelpers/contrib/templating/jinja.py
+++ b/hooks/charmhelpers/contrib/templating/jinja.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 """
 Templating using the python-jinja2 package.
diff --git a/hooks/charmhelpers/core/__init__.py b/hooks/charmhelpers/core/__init__.py
index d1400a0..d7567b8 100644
--- a/hooks/charmhelpers/core/__init__.py
+++ b/hooks/charmhelpers/core/__init__.py
@@ -1,15 +1,13 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/hooks/charmhelpers/core/decorators.py b/hooks/charmhelpers/core/decorators.py
index bb05620..6ad41ee 100644
--- a/hooks/charmhelpers/core/decorators.py
+++ b/hooks/charmhelpers/core/decorators.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 #
 # Copyright 2014 Canonical Ltd.
diff --git a/hooks/charmhelpers/core/files.py b/hooks/charmhelpers/core/files.py
index 0f12d32..fdd82b7 100644
--- a/hooks/charmhelpers/core/files.py
+++ b/hooks/charmhelpers/core/files.py
@@ -3,19 +3,17 @@
 
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 __author__ = 'Jorge Niedbalski <[e-mail]>'
 
diff --git a/hooks/charmhelpers/core/fstab.py b/hooks/charmhelpers/core/fstab.py
index 3056fba..d9fa915 100644
--- a/hooks/charmhelpers/core/fstab.py
+++ b/hooks/charmhelpers/core/fstab.py
@@ -3,19 +3,17 @@
 
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import io
 import os
diff --git a/hooks/charmhelpers/core/hookenv.py b/hooks/charmhelpers/core/hookenv.py
index 454b52a..996e81c 100644
--- a/hooks/charmhelpers/core/hookenv.py
+++ b/hooks/charmhelpers/core/hookenv.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 "Interactions with the Juju environment"
 # Copyright 2013 Canonical Ltd.
@@ -492,7 +490,7 @@ def relation_types():
 
 @cached
 def peer_relation_id():
-    '''Get a peer relation id if a peer relation has been joined, else None.'''
+    '''Get the peers relation id if a peers relation has been joined, else None.'''
     md = metadata()
     section = md.get('peers')
     if section:
@@ -517,12 +515,12 @@ def relation_to_interface(relation_name):
 def relation_to_role_and_interface(relation_name):
     """
     Given the name of a relation, return the role and the name of the interface
-    that relation uses (where role is one of ``provides``, ``requires``, or ``peer``).
+    that relation uses (where role is one of ``provides``, ``requires``, or ``peers``).
 
     :returns: A tuple containing ``(role, interface)``, or ``(None, None)``.
     """
     _metadata = metadata()
-    for role in ('provides', 'requires', 'peer'):
+    for role in ('provides', 'requires', 'peers'):
         interface = _metadata.get(role, {}).get(relation_name, {}).get('interface')
         if interface:
             return role, interface
@@ -534,7 +532,7 @@ def role_and_interface_to_relations(role, interface_name):
     """
     Given a role and interface name, return a list of relation names for the
     current charm that use that interface under that role (where role is one
-    of ``provides``, ``requires``, or ``peer``).
+    of ``provides``, ``requires``, or ``peers``).
 
     :returns: A list of relation names.
     """
@@ -555,7 +553,7 @@ def interface_to_relations(interface_name):
     :returns: A list of relation names.
     """
     results = []
-    for role in ('provides', 'requires', 'peer'):
+    for role in ('provides', 'requires', 'peers'):
         results.extend(role_and_interface_to_relations(role, interface_name))
     return results
 
@@ -637,7 +635,7 @@ def unit_private_ip():
 
 
 @cached
-def storage_get(attribute="", storage_id=""):
+def storage_get(attribute=None, storage_id=None):
     """Get storage attributes"""
     _args = ['storage-get', '--format=json']
     if storage_id:
@@ -651,7 +649,7 @@ def storage_get(attribute="", storage_id=""):
 
 
 @cached
-def storage_list(storage_name=""):
+def storage_list(storage_name=None):
     """List the storage IDs for the unit"""
     _args = ['storage-list', '--format=json']
     if storage_name:
@@ -845,6 +843,20 @@ def translate_exc(from_exc, to_exc):
     return inner_translate_exc1
 
 
+def application_version_set(version):
+    """Charm authors may trigger this command from any hook to output what
+    version of the application is running. This could be a package version,
+    for instance postgres version 9.5. It could also be a build number or
+    version control revision identifier, for instance git sha 6fb7ba68. """
+
+    cmd = ['application-version-set']
+    cmd.append(version)
+    try:
+        subprocess.check_call(cmd)
+    except OSError:
+        log("Application Version: {}".format(version))
+
+
 @translate_exc(from_exc=OSError, to_exc=NotImplementedError)
 def is_leader():
     """Does the current unit hold the juju leadership
@@ -878,6 +890,58 @@ def leader_set(settings=None, **kwargs):
     subprocess.check_call(cmd)
 
 
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def payload_register(ptype, klass, pid):
+    """ is used while a hook is running to let Juju know that a
+        payload has been started."""
+    cmd = ['payload-register']
+    for x in [ptype, klass, pid]:
+        cmd.append(x)
+    subprocess.check_call(cmd)
+
+
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def payload_unregister(klass, pid):
+    """ is used while a hook is running to let Juju know
+    that a payload has been manually stopped. The <class> and <id> provided
+    must match a payload that has been previously registered with juju using
+    payload-register."""
+    cmd = ['payload-unregister']
+    for x in [klass, pid]:
+        cmd.append(x)
+    subprocess.check_call(cmd)
+
+
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def payload_status_set(klass, pid, status):
+    """is used to update the current status of a registered payload.
+    The <class> and <id> provided must match a payload that has been previously
+    registered with juju using payload-register. The <status> must be one of the
+    follow: starting, started, stopping, stopped"""
+    cmd = ['payload-status-set']
+    for x in [klass, pid, status]:
+        cmd.append(x)
+    subprocess.check_call(cmd)
+
+
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def resource_get(name):
+    """used to fetch the resource path of the given name.
+
+    <name> must match a name of defined resource in metadata.yaml
+
+    returns either a path or False if resource not available
+    """
+    if not name:
+        return False
+
+    cmd = ['resource-get', name]
+    try:
+        return subprocess.check_output(cmd).decode('UTF-8')
+    except subprocess.CalledProcessError:
+        return False
+
+
 @cached
 def juju_version():
     """Full version string (eg. '1.23.3.1-trusty-amd64')"""
@@ -942,3 +1006,16 @@ def _run_atexit():
     for callback, args, kwargs in reversed(_atexit):
         callback(*args, **kwargs)
     del _atexit[:]
+
+
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def network_get_primary_address(binding):
+    '''
+    Retrieve the primary network address for a named binding
+
+    :param binding: string. The name of a relation of extra-binding
+    :return: string. The primary IP address for the named binding
+    :raise: NotImplementedError if run on Juju < 2.0
+    '''
+    cmd = ['network-get', '--primary-address', binding]
+    return subprocess.check_output(cmd).decode('UTF-8').strip()
diff --git a/hooks/charmhelpers/core/host.py b/hooks/charmhelpers/core/host.py
index 0d9c64f..0f1b2f3 100644
--- a/hooks/charmhelpers/core/host.py
+++ b/hooks/charmhelpers/core/host.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 """Tools for working with the host system"""
 # Copyright 2012 Canonical Ltd.
@@ -30,13 +28,31 @@ import random
 import string
 import subprocess
 import hashlib
-from contextlib import contextmanager
-from collections import OrderedDict
-
+import functools
+import itertools
 import six
 
+from contextlib import contextmanager
+from collections import OrderedDict
 from .hookenv import log
 from .fstab import Fstab
+from charmhelpers.osplatform import get_platform
+
+__platform__ = get_platform()
+if __platform__ == "ubuntu":
+    from charmhelpers.core.host_factory.ubuntu import (
+        service_available,
+        add_new_group,
+        lsb_release,
+        cmp_pkgrevno,
+    )  # flake8: noqa -- ignore F401 for this import
+elif __platform__ == "centos":
+    from charmhelpers.core.host_factory.centos import (
+        service_available,
+        add_new_group,
+        lsb_release,
+        cmp_pkgrevno,
+    )  # flake8: noqa -- ignore F401 for this import
 
 
 def service_start(service_name):
@@ -67,10 +83,14 @@ def service_pause(service_name, init_dir="/etc/init", initd_dir="/etc/init.d"):
     """Pause a system service.
 
     Stop it, and prevent it from starting again at boot."""
-    stopped = service_stop(service_name)
+    stopped = True
+    if service_running(service_name):
+        stopped = service_stop(service_name)
     upstart_file = os.path.join(init_dir, "{}.conf".format(service_name))
     sysv_file = os.path.join(initd_dir, service_name)
-    if os.path.exists(upstart_file):
+    if init_is_systemd():
+        service('disable', service_name)
+    elif os.path.exists(upstart_file):
         override_path = os.path.join(
             init_dir, '{}.override'.format(service_name))
         with open(override_path, 'w') as fh:
@@ -78,9 +98,9 @@ def service_pause(service_name, init_dir="/etc/init", initd_dir="/etc/init.d"):
     elif os.path.exists(sysv_file):
         subprocess.check_call(["update-rc.d", service_name, "disable"])
     else:
-        # XXX: Support SystemD too
         raise ValueError(
-            "Unable to detect {0} as either Upstart {1} or SysV {2}".format(
+            "Unable to detect {0} as SystemD, Upstart {1} or"
+            " SysV {2}".format(
                 service_name, upstart_file, sysv_file))
     return stopped
 
@@ -92,7 +112,9 @@ def service_resume(service_name, init_dir="/etc/init",
     Reenable starting again at boot. Start the service"""
     upstart_file = os.path.join(init_dir, "{}.conf".format(service_name))
     sysv_file = os.path.join(initd_dir, service_name)
-    if os.path.exists(upstart_file):
+    if init_is_systemd():
+        service('enable', service_name)
+    elif os.path.exists(upstart_file):
         override_path = os.path.join(
             init_dir, '{}.override'.format(service_name))
         if os.path.exists(override_path):
@@ -100,56 +122,95 @@ def service_resume(service_name, init_dir="/etc/init",
     elif os.path.exists(sysv_file):
         subprocess.check_call(["update-rc.d", service_name, "enable"])
     else:
-        # XXX: Support SystemD too
         raise ValueError(
-            "Unable to detect {0} as either Upstart {1} or SysV {2}".format(
+            "Unable to detect {0} as SystemD, Upstart {1} or"
+            " SysV {2}".format(
                 service_name, upstart_file, sysv_file))
 
-    started = service_start(service_name)
+    started = service_running(service_name)
+    if not started:
+        started = service_start(service_name)
     return started
 
 
 def service(action, service_name):
     """Control a system service"""
-    cmd = ['service', service_name, action]
+    if init_is_systemd():
+        cmd = ['systemctl', action, service_name]
+    else:
+        cmd = ['service', service_name, action]
     return subprocess.call(cmd) == 0
 
 
-def service_running(service):
+_UPSTART_CONF = "/etc/init/{}.conf"
+_INIT_D_CONF = "/etc/init.d/{}"
+
+
+def service_running(service_name):
     """Determine whether a system service is running"""
-    try:
-        output = subprocess.check_output(
-            ['service', service, 'status'],
-            stderr=subprocess.STDOUT).decode('UTF-8')
-    except subprocess.CalledProcessError:
-        return False
+    if init_is_systemd():
+        return service('is-active', service_name)
     else:
-        if ("start/running" in output or "is running" in output):
-            return True
-        else:
-            return False
+        if os.path.exists(_UPSTART_CONF.format(service_name)):
+            try:
+                output = subprocess.check_output(
+                    ['status', service_name],
+                    stderr=subprocess.STDOUT).decode('UTF-8')
+            except subprocess.CalledProcessError:
+                return False
+            else:
+                # This works for upstart scripts where the 'service' command
+                # returns a consistent string to represent running
+                # 'start/running'
+                if ("start/running" in output or
+                        "is running" in output or
+                        "up and running" in output):
+                    return True
+        elif os.path.exists(_INIT_D_CONF.format(service_name)):
+            # Check System V scripts init script return codes
+            return service('status', service_name)
+        return False
 
 
-def service_available(service_name):
-    """Determine whether a system service is available"""
-    try:
-        subprocess.check_output(
-            ['service', service_name, 'status'],
-            stderr=subprocess.STDOUT).decode('UTF-8')
-    except subprocess.CalledProcessError as e:
-        return b'unrecognized service' not in e.output
-    else:
-        return True
+SYSTEMD_SYSTEM = '/run/systemd/system'
+
+
+def init_is_systemd():
+    """Return True if the host system uses systemd, False otherwise."""
+    return os.path.isdir(SYSTEMD_SYSTEM)
+
 
+def adduser(username, password=None, shell='/bin/bash',
+            system_user=False, primary_group=None,
+            secondary_groups=None, uid=None, home_dir=None):
+    """Add a user to the system.
 
-def adduser(username, password=None, shell='/bin/bash', system_user=False):
-    """Add a user to the system"""
+    Will log but otherwise succeed if the user already exists.
+
+    :param str username: Username to create
+    :param str password: Password for user; if ``None``, create a system user
+    :param str shell: The default shell for the user
+    :param bool system_user: Whether to create a login or system user
+    :param str primary_group: Primary group for user; defaults to username
+    :param list secondary_groups: Optional list of additional groups
+    :param int uid: UID for user being created
+    :param str home_dir: Home directory for user
+
+    :returns: The password database entry struct, as returned by `pwd.getpwnam`
+    """
     try:
         user_info = pwd.getpwnam(username)
         log('user {0} already exists!'.format(username))
+        if uid:
+            user_info = pwd.getpwuid(int(uid))
+            log('user with uid {0} already exists!'.format(uid))
     except KeyError:
         log('creating user {0}'.format(username))
         cmd = ['useradd']
+        if uid:
+            cmd.extend(['--uid', str(uid)])
+        if home_dir:
+            cmd.extend(['--home', str(home_dir)])
         if system_user or password is None:
             cmd.append('--system')
         else:
@@ -158,6 +219,16 @@ def adduser(username, password=None, shell='/bin/bash', system_user=False):
                 '--shell', shell,
                 '--password', password,
             ])
+        if not primary_group:
+            try:
+                grp.getgrnam(username)
+                primary_group = username  # avoid "group exists" error
+            except KeyError:
+                pass
+        if primary_group:
+            cmd.extend(['-g', primary_group])
+        if secondary_groups:
+            cmd.extend(['-G', ','.join(secondary_groups)])
         cmd.append(username)
         subprocess.check_call(cmd)
         user_info = pwd.getpwnam(username)
@@ -174,22 +245,56 @@ def user_exists(username):
     return user_exists
 
 
-def add_group(group_name, system_group=False):
-    """Add a group to the system"""
+def uid_exists(uid):
+    """Check if a uid exists"""
+    try:
+        pwd.getpwuid(uid)
+        uid_exists = True
+    except KeyError:
+        uid_exists = False
+    return uid_exists
+
+
+def group_exists(groupname):
+    """Check if a group exists"""
+    try:
+        grp.getgrnam(groupname)
+        group_exists = True
+    except KeyError:
+        group_exists = False
+    return group_exists
+
+
+def gid_exists(gid):
+    """Check if a gid exists"""
+    try:
+        grp.getgrgid(gid)
+        gid_exists = True
+    except KeyError:
+        gid_exists = False
+    return gid_exists
+
+
+def add_group(group_name, system_group=False, gid=None):
+    """Add a group to the system
+
+    Will log but otherwise succeed if the group already exists.
+
+    :param str group_name: group to create
+    :param bool system_group: Create system group
+    :param int gid: GID for user being created
+
+    :returns: The password database entry struct, as returned by `grp.getgrnam`
+    """
     try:
         group_info = grp.getgrnam(group_name)
         log('group {0} already exists!'.format(group_name))
+        if gid:
+            group_info = grp.getgrgid(gid)
+            log('group with gid {0} already exists!'.format(gid))
     except KeyError:
         log('creating group {0}'.format(group_name))
-        cmd = ['addgroup']
-        if system_group:
-            cmd.append('--system')
-        else:
-            cmd.extend([
-                '--group',
-            ])
-        cmd.append(group_name)
-        subprocess.check_call(cmd)
+        add_new_group(group_name, system_group, gid)
         group_info = grp.getgrnam(group_name)
     return group_info
 
@@ -255,14 +360,12 @@ def write_file(path, content, owner='root', group='root', perms=0o444):
 
 
 def fstab_remove(mp):
-    """Remove the given mountpoint entry from /etc/fstab
-    """
+    """Remove the given mountpoint entry from /etc/fstab"""
     return Fstab.remove_by_mountpoint(mp)
 
 
 def fstab_add(dev, mp, fs, options=None):
-    """Adds the given device entry to the /etc/fstab file
-    """
+    """Adds the given device entry to the /etc/fstab file"""
     return Fstab.add(dev, mp, fs, options=options)
 
 
@@ -318,8 +421,7 @@ def fstab_mount(mountpoint):
 
 
 def file_hash(path, hash_type='md5'):
-    """
-    Generate a hash checksum of the contents of 'path' or None if not found.
+    """Generate a hash checksum of the contents of 'path' or None if not found.
 
     :param str hash_type: Any hash alrgorithm supported by :mod:`hashlib`,
                           such as md5, sha1, sha256, sha512, etc.
@@ -334,10 +436,9 @@ def file_hash(path, hash_type='md5'):
 
 
 def path_hash(path):
-    """
-    Generate a hash checksum of all files matching 'path'. Standard wildcards
-    like '*' and '?' are supported, see documentation for the 'glob' module for
-    more information.
+    """Generate a hash checksum of all files matching 'path'. Standard
+    wildcards like '*' and '?' are supported, see documentation for the 'glob'
+    module for more information.
 
     :return: dict: A { filename: hash } dictionary for all matched files.
                    Empty if none found.
@@ -349,8 +450,7 @@ def path_hash(path):
 
 
 def check_hash(path, checksum, hash_type='md5'):
-    """
-    Validate a file using a cryptographic checksum.
+    """Validate a file using a cryptographic checksum.
 
     :param str checksum: Value of the checksum used to validate the file.
     :param str hash_type: Hash algorithm used to generate `checksum`.
@@ -365,10 +465,11 @@ def check_hash(path, checksum, hash_type='md5'):
 
 
 class ChecksumError(ValueError):
+    """A class derived from Value error to indicate the checksum failed."""
     pass
 
 
-def restart_on_change(restart_map, stopstart=False):
+def restart_on_change(restart_map, stopstart=False, restart_functions=None):
     """Restart services based on configuration files changing
 
     This function is used a decorator, for example::
@@ -386,35 +487,56 @@ def restart_on_change(restart_map, stopstart=False):
     restarted if any file matching the pattern got changed, created
     or removed. Standard wildcards are supported, see documentation
     for the 'glob' module for more information.
+
+    @param restart_map: {path_file_name: [service_name, ...]
+    @param stopstart: DEFAULT false; whether to stop, start OR restart
+    @param restart_functions: nonstandard functions to use to restart services
+                              {svc: func, ...}
+    @returns result from decorated function
     """
     def wrap(f):
+        @functools.wraps(f)
         def wrapped_f(*args, **kwargs):
-            checksums = {path: path_hash(path) for path in restart_map}
-            f(*args, **kwargs)
-            restarts = []
-            for path in restart_map:
-                if path_hash(path) != checksums[path]:
-                    restarts += restart_map[path]
-            services_list = list(OrderedDict.fromkeys(restarts))
-            if not stopstart:
-                for service_name in services_list:
-                    service('restart', service_name)
-            else:
-                for action in ['stop', 'start']:
-                    for service_name in services_list:
-                        service(action, service_name)
+            return restart_on_change_helper(
+                (lambda: f(*args, **kwargs)), restart_map, stopstart,
+                restart_functions)
         return wrapped_f
     return wrap
 
 
-def lsb_release():
-    """Return /etc/lsb-release in a dict"""
-    d = {}
-    with open('/etc/lsb-release', 'r') as lsb:
-        for l in lsb:
-            k, v = l.split('=')
-            d[k.strip()] = v.strip()
-    return d
+def restart_on_change_helper(lambda_f, restart_map, stopstart=False,
+                             restart_functions=None):
+    """Helper function to perform the restart_on_change function.
+
+    This is provided for decorators to restart services if files described
+    in the restart_map have changed after an invocation of lambda_f().
+
+    @param lambda_f: function to call.
+    @param restart_map: {file: [service, ...]}
+    @param stopstart: whether to stop, start or restart a service
+    @param restart_functions: nonstandard functions to use to restart services
+                              {svc: func, ...}
+    @returns result of lambda_f()
+    """
+    if restart_functions is None:
+        restart_functions = {}
+    checksums = {path: path_hash(path) for path in restart_map}
+    r = lambda_f()
+    # create a list of lists of the services to restart
+    restarts = [restart_map[path]
+                for path in restart_map
+                if path_hash(path) != checksums[path]]
+    # create a flat list of ordered services without duplicates from lists
+    services_list = list(OrderedDict.fromkeys(itertools.chain(*restarts)))
+    if services_list:
+        actions = ('stop', 'start') if stopstart else ('restart',)
+        for service_name in services_list:
+            if service_name in restart_functions:
+                restart_functions[service_name](service_name)
+            else:
+                for action in actions:
+                    service(action, service_name)
+    return r
 
 
 def pwgen(length=None):
@@ -470,7 +592,7 @@ def get_bond_master(interface):
 
 
 def list_nics(nic_type=None):
-    '''Return a list of nics of given type(s)'''
+    """Return a list of nics of given type(s)"""
     if isinstance(nic_type, six.string_types):
         int_types = [nic_type]
     else:
@@ -512,12 +634,13 @@ def list_nics(nic_type=None):
 
 
 def set_nic_mtu(nic, mtu):
-    '''Set MTU on a network interface'''
+    """Set the Maximum Transmission Unit (MTU) on a network interface."""
     cmd = ['ip', 'link', 'set', nic, 'mtu', mtu]
     subprocess.check_call(cmd)
 
 
 def get_nic_mtu(nic):
+    """Return the Maximum Transmission Unit (MTU) for a network interface."""
     cmd = ['ip', 'addr', 'show', nic]
     ip_output = subprocess.check_output(cmd).decode('UTF-8').split('\n')
     mtu = ""
@@ -529,6 +652,7 @@ def get_nic_mtu(nic):
 
 
 def get_nic_hwaddr(nic):
+    """Return the Media Access Control (MAC) for a network interface."""
     cmd = ['ip', '-o', '-0', 'addr', 'show', nic]
     ip_output = subprocess.check_output(cmd).decode('UTF-8')
     hwaddr = ""
@@ -538,39 +662,28 @@ def get_nic_hwaddr(nic):
     return hwaddr
 
 
-def cmp_pkgrevno(package, revno, pkgcache=None):
-    '''Compare supplied revno with the revno of the installed package
-
-    *  1 => Installed revno is greater than supplied arg
-    *  0 => Installed revno is the same as supplied arg
-    * -1 => Installed revno is less than supplied arg
-
-    This function imports apt_cache function from charmhelpers.fetch if
-    the pkgcache argument is None. Be sure to add charmhelpers.fetch if
-    you call this function, or pass an apt_pkg.Cache() instance.
-    '''
-    import apt_pkg
-    if not pkgcache:
-        from charmhelpers.fetch import apt_cache
-        pkgcache = apt_cache()
-    pkg = pkgcache[package]
-    return apt_pkg.version_compare(pkg.current_ver.ver_str, revno)
-
-
 @contextmanager
-def chdir(d):
+def chdir(directory):
+    """Change the current working directory to a different directory for a code
+    block and return the previous directory after the block exits. Useful to
+    run commands from a specificed directory.
+
+    :param str directory: The directory path to change to for this context.
+    """
     cur = os.getcwd()
     try:
-        yield os.chdir(d)
+        yield os.chdir(directory)
     finally:
         os.chdir(cur)
 
 
 def chownr(path, owner, group, follow_links=True, chowntopdir=False):
-    """
-    Recursively change user and group ownership of files and directories
+    """Recursively change user and group ownership of files and directories
     in given path. Doesn't chown path itself by default, only its children.
 
+    :param str path: The string path to start changing ownership.
+    :param str owner: The owner string to use when looking up the uid.
+    :param str group: The group string to use when looking up the gid.
     :param bool follow_links: Also Chown links if True
     :param bool chowntopdir: Also chown path itself if True
     """
@@ -594,15 +707,23 @@ def chownr(path, owner, group, follow_links=True, chowntopdir=False):
 
 
 def lchownr(path, owner, group):
+    """Recursively change user and group ownership of files and directories
+    in a given path, not following symbolic links. See the documentation for
+    'os.lchown' for more information.
+
+    :param str path: The string path to start changing ownership.
+    :param str owner: The owner string to use when looking up the uid.
+    :param str group: The group string to use when looking up the gid.
+    """
     chownr(path, owner, group, follow_links=False)
 
 
 def get_total_ram():
-    '''The total amount of system RAM in bytes.
+    """The total amount of system RAM in bytes.
 
     This is what is reported by the OS, and may be overcommitted when
     there are multiple containers hosted on the same machine.
-    '''
+    """
     with open('/proc/meminfo', 'r') as f:
         for line in f.readlines():
             if line:
diff --git a/hooks/charmhelpers/core/host_factory/__init__.py b/hooks/charmhelpers/core/host_factory/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/hooks/charmhelpers/core/host_factory/__init__.py
diff --git a/hooks/charmhelpers/core/host_factory/centos.py b/hooks/charmhelpers/core/host_factory/centos.py
new file mode 100644
index 0000000..902d469
--- /dev/null
+++ b/hooks/charmhelpers/core/host_factory/centos.py
@@ -0,0 +1,56 @@
+import subprocess
+import yum
+import os
+
+
+def service_available(service_name):
+    # """Determine whether a system service is available."""
+    if os.path.isdir('/run/systemd/system'):
+        cmd = ['systemctl', 'is-enabled', service_name]
+    else:
+        cmd = ['service', service_name, 'is-enabled']
+    return subprocess.call(cmd) == 0
+
+
+def add_new_group(group_name, system_group=False, gid=None):
+    cmd = ['groupadd']
+    if gid:
+        cmd.extend(['--gid', str(gid)])
+    if system_group:
+        cmd.append('-r')
+    cmd.append(group_name)
+    subprocess.check_call(cmd)
+
+
+def lsb_release():
+    """Return /etc/os-release in a dict."""
+    d = {}
+    with open('/etc/os-release', 'r') as lsb:
+        for l in lsb:
+            s = l.split('=')
+            if len(s) != 2:
+                continue
+            d[s[0].strip()] = s[1].strip()
+    return d
+
+
+def cmp_pkgrevno(package, revno, pkgcache=None):
+    """Compare supplied revno with the revno of the installed package.
+
+    *  1 => Installed revno is greater than supplied arg
+    *  0 => Installed revno is the same as supplied arg
+    * -1 => Installed revno is less than supplied arg
+
+    This function imports YumBase function if the pkgcache argument
+    is None.
+    """
+    if not pkgcache:
+        y = yum.YumBase()
+        packages = y.doPackageLists()
+        pkgcache = {i.Name: i.version for i in packages['installed']}
+    pkg = pkgcache[package]
+    if pkg > revno:
+        return 1
+    if pkg < revno:
+        return -1
+    return 0
diff --git a/hooks/charmhelpers/core/host_factory/ubuntu.py b/hooks/charmhelpers/core/host_factory/ubuntu.py
new file mode 100644
index 0000000..8c66af5
--- /dev/null
+++ b/hooks/charmhelpers/core/host_factory/ubuntu.py
@@ -0,0 +1,56 @@
+import subprocess
+
+
+def service_available(service_name):
+    """Determine whether a system service is available"""
+    try:
+        subprocess.check_output(
+            ['service', service_name, 'status'],
+            stderr=subprocess.STDOUT).decode('UTF-8')
+    except subprocess.CalledProcessError as e:
+        return b'unrecognized service' not in e.output
+    else:
+        return True
+
+
+def add_new_group(group_name, system_group=False, gid=None):
+    cmd = ['addgroup']
+    if gid:
+        cmd.extend(['--gid', str(gid)])
+    if system_group:
+        cmd.append('--system')
+    else:
+        cmd.extend([
+            '--group',
+        ])
+    cmd.append(group_name)
+    subprocess.check_call(cmd)
+
+
+def lsb_release():
+    """Return /etc/lsb-release in a dict"""
+    d = {}
+    with open('/etc/lsb-release', 'r') as lsb:
+        for l in lsb:
+            k, v = l.split('=')
+            d[k.strip()] = v.strip()
+    return d
+
+
+def cmp_pkgrevno(package, revno, pkgcache=None):
+    """Compare supplied revno with the revno of the installed package.
+
+    *  1 => Installed revno is greater than supplied arg
+    *  0 => Installed revno is the same as supplied arg
+    * -1 => Installed revno is less than supplied arg
+
+    This function imports apt_cache function from charmhelpers.fetch if
+    the pkgcache argument is None. Be sure to add charmhelpers.fetch if
+    you call this function, or pass an apt_pkg.Cache() instance.
+    """
+    import apt_pkg
+    if not pkgcache:
+        from charmhelpers.fetch import apt_cache
+        pkgcache = apt_cache()
+    pkg = pkgcache[package]
+    return apt_pkg.version_compare(pkg.current_ver.ver_str, revno)
diff --git a/hooks/charmhelpers/core/hugepage.py b/hooks/charmhelpers/core/hugepage.py
index a783ad9..54b5b5e 100644
--- a/hooks/charmhelpers/core/hugepage.py
+++ b/hooks/charmhelpers/core/hugepage.py
@@ -2,19 +2,17 @@
 
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import yaml
 from charmhelpers.core import fstab
diff --git a/hooks/charmhelpers/core/kernel.py b/hooks/charmhelpers/core/kernel.py
index 5dc6495..2d40452 100644
--- a/hooks/charmhelpers/core/kernel.py
+++ b/hooks/charmhelpers/core/kernel.py
@@ -3,29 +3,40 @@
 
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
-__author__ = "Jorge Niedbalski <[e-mail]>"
+import re
+import subprocess
 
+from charmhelpers.osplatform import get_platform
 from charmhelpers.core.hookenv import (
     log,
     INFO
 )
 
-from subprocess import check_call, check_output
-import re
+__platform__ = get_platform()
+if __platform__ == "ubuntu":
+    from charmhelpers.core.kernel_factory.ubuntu import (
+        persistent_modprobe,
+        update_initramfs,
+    )  # flake8: noqa -- ignore F401 for this import
+elif __platform__ == "centos":
+    from charmhelpers.core.kernel_factory.centos import (
+        persistent_modprobe,
+        update_initramfs,
+    )  # flake8: noqa -- ignore F401 for this import
+
+__author__ = "Jorge Niedbalski <[e-mail]>"
 
 
 def modprobe(module, persist=True):
@@ -34,11 +45,9 @@ def modprobe(module, persist=True):
 
     log('Loading kernel module %s' % module, level=INFO)
 
-    check_call(cmd)
+    subprocess.check_call(cmd)
     if persist:
-        with open('/etc/modules', 'r+') as modules:
-            if module not in modules.read():
-                modules.write(module)
+        persistent_modprobe(module)
 
 
 def rmmod(module, force=False):
@@ -48,21 +57,16 @@ def rmmod(module, force=False):
         cmd.append('-f')
     cmd.append(module)
     log('Removing kernel module %s' % module, level=INFO)
-    return check_call(cmd)
+    return subprocess.check_call(cmd)
 
 
 def lsmod():
     """Shows what kernel modules are currently loaded"""
-    return check_output(['lsmod'],
-                        universal_newlines=True)
+    return subprocess.check_output(['lsmod'],
+                                   universal_newlines=True)
 
 
 def is_module_loaded(module):
     """Checks if a kernel module is already loaded"""
     matches = re.findall('^%s[ ]+' % module, lsmod(), re.M)
     return len(matches) > 0
-
-
-def update_initramfs(version='all'):
-    """Updates an initramfs image"""
-    return check_call(["update-initramfs", "-k", version, "-u"])
diff --git a/hooks/charmhelpers/core/kernel_factory/__init__.py b/hooks/charmhelpers/core/kernel_factory/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/hooks/charmhelpers/core/kernel_factory/__init__.py
diff --git a/hooks/charmhelpers/core/kernel_factory/centos.py b/hooks/charmhelpers/core/kernel_factory/centos.py
new file mode 100644
index 0000000..1c402c1
--- /dev/null
+++ b/hooks/charmhelpers/core/kernel_factory/centos.py
@@ -0,0 +1,17 @@
+import subprocess
+import os
+
+
+def persistent_modprobe(module):
+    """Load a kernel module and configure for auto-load on reboot."""
+    if not os.path.exists('/etc/rc.modules'):
+        open('/etc/rc.modules', 'a')
+        os.chmod('/etc/rc.modules', 111)
+    with open('/etc/rc.modules', 'r+') as modules:
+        if module not in modules.read():
+            modules.write('modprobe %s\n' % module)
+
+
+def update_initramfs(version='all'):
+    """Updates an initramfs image."""
+    return subprocess.check_call(["dracut", "-f", version])
diff --git a/hooks/charmhelpers/core/kernel_factory/ubuntu.py b/hooks/charmhelpers/core/kernel_factory/ubuntu.py
new file mode 100644
index 0000000..2155964
--- /dev/null
+++ b/hooks/charmhelpers/core/kernel_factory/ubuntu.py
@@ -0,0 +1,13 @@
+import subprocess
+
+
+def persistent_modprobe(module):
+    """Load a kernel module and configure for auto-load on reboot."""
+    with open('/etc/modules', 'r+') as modules:
+        if module not in modules.read():
+            modules.write(module)
+
+
+def update_initramfs(version='all'):
+    """Updates an initramfs image."""
+    return subprocess.check_call(["update-initramfs", "-k", version, "-u"])
diff --git a/hooks/charmhelpers/core/services/__init__.py b/hooks/charmhelpers/core/services/__init__.py
index 0928158..61fd074 100644
--- a/hooks/charmhelpers/core/services/__init__.py
+++ b/hooks/charmhelpers/core/services/__init__.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 from .base import *  # NOQA
 from .helpers import *  # NOQA
diff --git a/hooks/charmhelpers/core/services/base.py b/hooks/charmhelpers/core/services/base.py
index a42660c..ca9dc99 100644
--- a/hooks/charmhelpers/core/services/base.py
+++ b/hooks/charmhelpers/core/services/base.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import os
 import json
diff --git a/hooks/charmhelpers/core/services/helpers.py b/hooks/charmhelpers/core/services/helpers.py
index 12d768e..3e6e30d 100644
--- a/hooks/charmhelpers/core/services/helpers.py
+++ b/hooks/charmhelpers/core/services/helpers.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import os
 import yaml
@@ -243,13 +241,15 @@ class TemplateCallback(ManagerCallback):
     :param str source: The template source file, relative to
         `$CHARM_DIR/templates`
 
-    :param str target: The target to write the rendered template to
+    :param str target: The target to write the rendered template to (or None)
     :param str owner: The owner of the rendered file
     :param str group: The group of the rendered file
     :param int perms: The permissions of the rendered file
     :param partial on_change_action: functools partial to be executed when
                                      rendered file changes
     :param jinja2 loader template_loader: A jinja2 template loader
+
+    :return str: The rendered template
     """
     def __init__(self, source, target,
                  owner='root', group='root', perms=0o444,
@@ -267,12 +267,14 @@ class TemplateCallback(ManagerCallback):
         if self.on_change_action and os.path.isfile(self.target):
             pre_checksum = host.file_hash(self.target)
         service = manager.get_service(service_name)
-        context = {}
+        context = {'ctx': {}}
         for ctx in service.get('required_data', []):
             context.update(ctx)
-        templating.render(self.source, self.target, context,
-                          self.owner, self.group, self.perms,
-                          template_loader=self.template_loader)
+            context['ctx'].update(ctx)
+
+        result = templating.render(self.source, self.target, context,
+                                   self.owner, self.group, self.perms,
+                                   template_loader=self.template_loader)
         if self.on_change_action:
             if pre_checksum == host.file_hash(self.target):
                 hookenv.log(
@@ -281,6 +283,8 @@ class TemplateCallback(ManagerCallback):
             else:
                 self.on_change_action()
 
+        return result
+
 
 # Convenience aliases for templates
 render_template = template = TemplateCallback
diff --git a/hooks/charmhelpers/core/strutils.py b/hooks/charmhelpers/core/strutils.py
index 7e3f969..dd9b971 100644
--- a/hooks/charmhelpers/core/strutils.py
+++ b/hooks/charmhelpers/core/strutils.py
@@ -3,19 +3,17 @@
 
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import six
 import re
diff --git a/hooks/charmhelpers/core/sysctl.py b/hooks/charmhelpers/core/sysctl.py
index 21cc8ab..6e413e3 100644
--- a/hooks/charmhelpers/core/sysctl.py
+++ b/hooks/charmhelpers/core/sysctl.py
@@ -3,19 +3,17 @@
 
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import yaml
 
diff --git a/hooks/charmhelpers/core/templating.py b/hooks/charmhelpers/core/templating.py
index 239719d..7b801a3 100644
--- a/hooks/charmhelpers/core/templating.py
+++ b/hooks/charmhelpers/core/templating.py
@@ -1,20 +1,19 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import os
+import sys
 
 from charmhelpers.core import host
 from charmhelpers.core import hookenv
@@ -27,7 +26,8 @@ def render(source, target, context, owner='root', group='root',
 
     The `source` path, if not absolute, is relative to the `templates_dir`.
 
-    The `target` path should be absolute.
+    The `target` path should be absolute.  It can also be `None`, in which
+    case no file will be written.
 
     The context should be a dict containing the values to be replaced in the
     template.
@@ -36,8 +36,12 @@ def render(source, target, context, owner='root', group='root',
 
     If omitted, `templates_dir` defaults to the `templates` folder in the charm.
 
-    Note: Using this requires python-jinja2; if it is not installed, calling
-    this will attempt to use charmhelpers.fetch.apt_install to install it.
+    The rendered template will be written to the file as well as being returned
+    as a string.
+
+    Note: Using this requires python-jinja2 or python3-jinja2; if it is not
+    installed, calling this will attempt to use charmhelpers.fetch.apt_install
+    to install it.
     """
     try:
         from jinja2 import FileSystemLoader, Environment, exceptions
@@ -49,7 +53,10 @@ def render(source, target, context, owner='root', group='root',
                         'charmhelpers.fetch to install it',
                         level=hookenv.ERROR)
             raise
-        apt_install('python-jinja2', fatal=True)
+        if sys.version_info.major == 2:
+            apt_install('python-jinja2', fatal=True)
+        else:
+            apt_install('python3-jinja2', fatal=True)
         from jinja2 import FileSystemLoader, Environment, exceptions
 
     if template_loader:
@@ -67,9 +74,11 @@ def render(source, target, context, owner='root', group='root',
                     level=hookenv.ERROR)
         raise e
     content = template.render(context)
-    target_dir = os.path.dirname(target)
-    if not os.path.exists(target_dir):
-        # This is a terrible default directory permission, as the file
-        # or its siblings will often contain secrets.
-        host.mkdir(os.path.dirname(target), owner, group, perms=0o755)
-    host.write_file(target, content.encode(encoding), owner, group, perms)
+    if target is not None:
+        target_dir = os.path.dirname(target)
+        if not os.path.exists(target_dir):
+            # This is a terrible default directory permission, as the file
+            # or its siblings will often contain secrets.
+            host.mkdir(os.path.dirname(target), owner, group, perms=0o755)
+        host.write_file(target, content.encode(encoding), owner, group, perms)
+    return content
diff --git a/hooks/charmhelpers/core/unitdata.py b/hooks/charmhelpers/core/unitdata.py
index 338104e..54ec969 100644
--- a/hooks/charmhelpers/core/unitdata.py
+++ b/hooks/charmhelpers/core/unitdata.py
@@ -3,20 +3,17 @@
 #
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
-#
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 #
 # Authors:
 #  Kapil Thangavelu <[e-mail]>
diff --git a/hooks/charmhelpers/fetch/__init__.py b/hooks/charmhelpers/fetch/__init__.py
index 5f831c3..ec5e0fe 100644
--- a/hooks/charmhelpers/fetch/__init__.py
+++ b/hooks/charmhelpers/fetch/__init__.py
@@ -1,32 +1,24 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import importlib
-from tempfile import NamedTemporaryFile
-import time
+from charmhelpers.osplatform import get_platform
 from yaml import safe_load
-from charmhelpers.core.host import (
-    lsb_release
-)
-import subprocess
 from charmhelpers.core.hookenv import (
     config,
     log,
 )
-import os
 
 import six
 if six.PY3:
@@ -35,71 +27,6 @@ else:
     from urlparse import urlparse, urlunparse
 
 
-CLOUD_ARCHIVE = """# Ubuntu Cloud Archive
-deb http://ubuntu-cloud.archive.canonical.com/ubuntu {} main
-"""
-PROPOSED_POCKET = """# Proposed
-deb http://archive.ubuntu.com/ubuntu {}-proposed main universe multiverse restricted
-"""
-CLOUD_ARCHIVE_POCKETS = {
-    # Folsom
-    'folsom': 'precise-updates/folsom',
-    'precise-folsom': 'precise-updates/folsom',
-    'precise-folsom/updates': 'precise-updates/folsom',
-    'precise-updates/folsom': 'precise-updates/folsom',
-    'folsom/proposed': 'precise-proposed/folsom',
-    'precise-folsom/proposed': 'precise-proposed/folsom',
-    'precise-proposed/folsom': 'precise-proposed/folsom',
-    # Grizzly
-    'grizzly': 'precise-updates/grizzly',
-    'precise-grizzly': 'precise-updates/grizzly',
-    'precise-grizzly/updates': 'precise-updates/grizzly',
-    'precise-updates/grizzly': 'precise-updates/grizzly',
-    'grizzly/proposed': 'precise-proposed/grizzly',
-    'precise-grizzly/proposed': 'precise-proposed/grizzly',
-    'precise-proposed/grizzly': 'precise-proposed/grizzly',
-    # Havana
-    'havana': 'precise-updates/havana',
-    'precise-havana': 'precise-updates/havana',
-    'precise-havana/updates': 'precise-updates/havana',
-    'precise-updates/havana': 'precise-updates/havana',
-    'havana/proposed': 'precise-proposed/havana',
-    'precise-havana/proposed': 'precise-proposed/havana',
-    'precise-proposed/havana': 'precise-proposed/havana',
-    # Icehouse
-    'icehouse': 'precise-updates/icehouse',
-    'precise-icehouse': 'precise-updates/icehouse',
-    'precise-icehouse/updates': 'precise-updates/icehouse',
-    'precise-updates/icehouse': 'precise-updates/icehouse',
-    'icehouse/proposed': 'precise-proposed/icehouse',
-    'precise-icehouse/proposed': 'precise-proposed/icehouse',
-    'precise-proposed/icehouse': 'precise-proposed/icehouse',
-    # Juno
-    'juno': 'trusty-updates/juno',
-    'trusty-juno': 'trusty-updates/juno',
-    'trusty-juno/updates': 'trusty-updates/juno',
-    'trusty-updates/juno': 'trusty-updates/juno',
-    'juno/proposed': 'trusty-proposed/juno',
-    'trusty-juno/proposed': 'trusty-proposed/juno',
-    'trusty-proposed/juno': 'trusty-proposed/juno',
-    # Kilo
-    'kilo': 'trusty-updates/kilo',
-    'trusty-kilo': 'trusty-updates/kilo',
-    'trusty-kilo/updates': 'trusty-updates/kilo',
-    'trusty-updates/kilo': 'trusty-updates/kilo',
-    'kilo/proposed': 'trusty-proposed/kilo',
-    'trusty-kilo/proposed': 'trusty-proposed/kilo',
-    'trusty-proposed/kilo': 'trusty-proposed/kilo',
-    # Liberty
-    'liberty': 'trusty-updates/liberty',
-    'trusty-liberty': 'trusty-updates/liberty',
-    'trusty-liberty/updates': 'trusty-updates/liberty',
-    'trusty-updates/liberty': 'trusty-updates/liberty',
-    'liberty/proposed': 'trusty-proposed/liberty',
-    'trusty-liberty/proposed': 'trusty-proposed/liberty',
-    'trusty-proposed/liberty': 'trusty-proposed/liberty',
-}
-
 # The order of this list is very important. Handlers should be listed in from
 # least- to most-specific URL matching.
 FETCH_HANDLERS = (
@@ -108,10 +35,6 @@ FETCH_HANDLERS = (
     'charmhelpers.fetch.giturl.GitUrlFetchHandler',
 )
 
-APT_NO_LOCK = 100  # The return code for "couldn't acquire lock" in APT.
-APT_NO_LOCK_RETRY_DELAY = 10  # Wait 10 seconds between apt lock checks.
-APT_NO_LOCK_RETRY_COUNT = 30  # Retry to acquire the lock X times.
-
 
 class SourceConfigError(Exception):
     pass
@@ -149,180 +72,38 @@ class BaseFetchHandler(object):
         return urlunparse(parts)
 
 
-def filter_installed_packages(packages):
-    """Returns a list of packages that require installation"""
-    cache = apt_cache()
-    _pkgs = []
-    for package in packages:
-        try:
-            p = cache[package]
-            p.current_ver or _pkgs.append(package)
-        except KeyError:
-            log('Package {} has no installation candidate.'.format(package),
-                level='WARNING')
-            _pkgs.append(package)
-    return _pkgs
-
-
-def apt_cache(in_memory=True):
-    """Build and return an apt cache"""
-    from apt import apt_pkg
-    apt_pkg.init()
-    if in_memory:
-        apt_pkg.config.set("Dir::Cache::pkgcache", "")
-        apt_pkg.config.set("Dir::Cache::srcpkgcache", "")
-    return apt_pkg.Cache()
-
-
-def apt_install(packages, options=None, fatal=False):
-    """Install one or more packages"""
-    if options is None:
-        options = ['--option=Dpkg::Options::=--force-confold']
-
-    cmd = ['apt-get', '--assume-yes']
-    cmd.extend(options)
-    cmd.append('install')
-    if isinstance(packages, six.string_types):
-        cmd.append(packages)
-    else:
-        cmd.extend(packages)
-    log("Installing {} with options: {}".format(packages,
-                                                options))
-    _run_apt_command(cmd, fatal)
-
-
-def apt_upgrade(options=None, fatal=False, dist=False):
-    """Upgrade all packages"""
-    if options is None:
-        options = ['--option=Dpkg::Options::=--force-confold']
-
-    cmd = ['apt-get', '--assume-yes']
-    cmd.extend(options)
-    if dist:
-        cmd.append('dist-upgrade')
-    else:
-        cmd.append('upgrade')
-    log("Upgrading with options: {}".format(options))
-    _run_apt_command(cmd, fatal)
-
-
-def apt_update(fatal=False):
-    """Update local apt cache"""
-    cmd = ['apt-get', 'update']
-    _run_apt_command(cmd, fatal)
-
-
-def apt_purge(packages, fatal=False):
-    """Purge one or more packages"""
-    cmd = ['apt-get', '--assume-yes', 'purge']
-    if isinstance(packages, six.string_types):
-        cmd.append(packages)
-    else:
-        cmd.extend(packages)
-    log("Purging {}".format(packages))
-    _run_apt_command(cmd, fatal)
-
-
-def apt_mark(packages, mark, fatal=False):
-    """Flag one or more packages using apt-mark"""
-    log("Marking {} as {}".format(packages, mark))
-    cmd = ['apt-mark', mark]
-    if isinstance(packages, six.string_types):
-        cmd.append(packages)
-    else:
-        cmd.extend(packages)
-
-    if fatal:
-        subprocess.check_call(cmd, universal_newlines=True)
-    else:
-        subprocess.call(cmd, universal_newlines=True)
+__platform__ = get_platform()
+module = "charmhelpers.fetch.%s" % __platform__
+fetch = importlib.import_module(module)
 
+filter_installed_packages = fetch.filter_installed_packages
+install = fetch.install
+upgrade = fetch.upgrade
+update = fetch.update
+purge = fetch.purge
+add_source = fetch.add_source
 
-def apt_hold(packages, fatal=False):
-    return apt_mark(packages, 'hold', fatal=fatal)
-
-
-def apt_unhold(packages, fatal=False):
-    return apt_mark(packages, 'unhold', fatal=fatal)
-
-
-def add_source(source, key=None):
-    """Add a package source to this system.
-
-    @param source: a URL or sources.list entry, as supported by
-    add-apt-repository(1). Examples::
-
-        ppa:charmers/example
-        deb https://stub:[e-mail]/ubuntu trusty main
-
-    In addition:
-        'proposed:' may be used to enable the standard 'proposed'
-        pocket for the release.
-        'cloud:' may be used to activate official cloud archive pockets,
-        such as 'cloud:icehouse'
-        'distro' may be used as a noop
-
-    @param key: A key to be added to the system's APT keyring and used
-    to verify the signatures on packages. Ideally, this should be an
-    ASCII format GPG public key including the block headers. A GPG key
-    id may also be used, but be aware that only insecure protocols are
-    available to retrieve the actual public key from a public keyserver
-    placing your Juju environment at risk. ppa and cloud archive keys
-    are securely added automtically, so sould not be provided.
-    """
-    if source is None:
-        log('Source is not present. Skipping')
-        return
-
-    if (source.startswith('ppa:') or
-        source.startswith('http') or
-        source.startswith('deb ') or
-            source.startswith('cloud-archive:')):
-        subprocess.check_call(['add-apt-repository', '--yes', source])
-    elif source.startswith('cloud:'):
-        apt_install(filter_installed_packages(['ubuntu-cloud-keyring']),
-                    fatal=True)
-        pocket = source.split(':')[-1]
-        if pocket not in CLOUD_ARCHIVE_POCKETS:
-            raise SourceConfigError(
-                'Unsupported cloud: source option %s' %
-                pocket)
-        actual_pocket = CLOUD_ARCHIVE_POCKETS[pocket]
-        with open('/etc/apt/sources.list.d/cloud-archive.list', 'w') as apt:
-            apt.write(CLOUD_ARCHIVE.format(actual_pocket))
-    elif source == 'proposed':
-        release = lsb_release()['DISTRIB_CODENAME']
-        with open('/etc/apt/sources.list.d/proposed.list', 'w') as apt:
-            apt.write(PROPOSED_POCKET.format(release))
-    elif source == 'distro':
-        pass
-    else:
-        log("Unknown source: {!r}".format(source))
-
-    if key:
-        if '-----BEGIN PGP PUBLIC KEY BLOCK-----' in key:
-            with NamedTemporaryFile('w+') as key_file:
-                key_file.write(key)
-                key_file.flush()
-                key_file.seek(0)
-                subprocess.check_call(['apt-key', 'add', '-'], stdin=key_file)
-        else:
-            # Note that hkp: is in no way a secure protocol. Using a
-            # GPG key id is pointless from a security POV unless you
-            # absolutely trust your network and DNS.
-            subprocess.check_call(['apt-key', 'adv', '--keyserver',
-                                   'hkp://keyserver.ubuntu.com:80', '--recv',
-                                   key])
+if __platform__ == "ubuntu":
+    apt_cache = fetch.apt_cache
+    apt_install = fetch.install
+    apt_update = fetch.update
+    apt_upgrade = fetch.upgrade
+    apt_purge = fetch.purge
+    apt_mark = fetch.apt_mark
+    apt_hold = fetch.apt_hold
+    apt_unhold = fetch.apt_unhold
+    get_upstream_version = fetch.get_upstream_version
+elif __platform__ == "centos":
+    yum_search = fetch.yum_search
 
 
 def configure_sources(update=False,
                       sources_var='install_sources',
                       keys_var='install_keys'):
-    """
-    Configure multiple sources from charm configuration.
+    """Configure multiple sources from charm configuration.
 
     The lists are encoded as yaml fragments in the configuration.
-    The frament needs to be included as a string. Sources and their
+    The fragment needs to be included as a string. Sources and their
     corresponding keys are of the types supported by add_source().
 
     Example config:
@@ -354,12 +135,11 @@ def configure_sources(update=False,
         for source, key in zip(sources, keys):
             add_source(source, key)
     if update:
-        apt_update(fatal=True)
+        fetch.update(fatal=True)
 
 
 def install_remote(source, *args, **kwargs):
-    """
-    Install a file tree from a remote source
+    """Install a file tree from a remote source.
 
     The specified source should be a url of the form:
         scheme://[host]/path[#[option=value][&...]]
@@ -382,19 +162,17 @@ def install_remote(source, *args, **kwargs):
     # We ONLY check for True here because can_handle may return a string
     # explaining why it can't handle a given source.
     handlers = [h for h in plugins() if h.can_handle(source) is True]
-    installed_to = None
     for handler in handlers:
         try:
-            installed_to = handler.install(source, *args, **kwargs)
+            return handler.install(source, *args, **kwargs)
         except UnhandledSource as e:
             log('Install source attempt unsuccessful: {}'.format(e),
                 level='WARNING')
-    if not installed_to:
-        raise UnhandledSource("No handler found for source {}".format(source))
-    return installed_to
+    raise UnhandledSource("No handler found for source {}".format(source))
 
 
 def install_from_config(config_var_name):
+    """Install a file from config."""
     charm_config = config()
     source = charm_config[config_var_name]
     return install_remote(source)
@@ -411,46 +189,9 @@ def plugins(fetch_handlers=None):
                 importlib.import_module(package),
                 classname)
             plugin_list.append(handler_class())
-        except (ImportError, AttributeError):
+        except NotImplementedError:
             # Skip missing plugins so that they can be ommitted from
             # installation if desired
             log("FetchHandler {} not found, skipping plugin".format(
                 handler_name))
     return plugin_list
-
-
-def _run_apt_command(cmd, fatal=False):
-    """
-    Run an APT command, checking output and retrying if the fatal flag is set
-    to True.
-
-    :param: cmd: str: The apt command to run.
-    :param: fatal: bool: Whether the command's output should be checked and
-        retried.
-    """
-    env = os.environ.copy()
-
-    if 'DEBIAN_FRONTEND' not in env:
-        env['DEBIAN_FRONTEND'] = 'noninteractive'
-
-    if fatal:
-        retry_count = 0
-        result = None
-
-        # If the command is considered "fatal", we need to retry if the apt
-        # lock was not acquired.
-
-        while result is None or result == APT_NO_LOCK:
-            try:
-                result = subprocess.check_call(cmd, env=env)
-            except subprocess.CalledProcessError as e:
-                retry_count = retry_count + 1
-                if retry_count > APT_NO_LOCK_RETRY_COUNT:
-                    raise
-                result = e.returncode
-                log("Couldn't acquire DPKG lock. Will retry in {} seconds."
-                    "".format(APT_NO_LOCK_RETRY_DELAY))
-                time.sleep(APT_NO_LOCK_RETRY_DELAY)
-
-    else:
-        subprocess.call(cmd, env=env)
diff --git a/hooks/charmhelpers/fetch/archiveurl.py b/hooks/charmhelpers/fetch/archiveurl.py
index efd7f9f..dd24f9e 100644
--- a/hooks/charmhelpers/fetch/archiveurl.py
+++ b/hooks/charmhelpers/fetch/archiveurl.py
@@ -1,18 +1,16 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import os
 import hashlib
@@ -108,7 +106,7 @@ class ArchiveUrlFetchHandler(BaseFetchHandler):
                 install_opener(opener)
         response = urlopen(source)
         try:
-            with open(dest, 'w') as dest_file:
+            with open(dest, 'wb') as dest_file:
                 dest_file.write(response.read())
         except Exception as e:
             if os.path.isfile(dest):
diff --git a/hooks/charmhelpers/fetch/bzrurl.py b/hooks/charmhelpers/fetch/bzrurl.py
index 3531315..07cd029 100644
--- a/hooks/charmhelpers/fetch/bzrurl.py
+++ b/hooks/charmhelpers/fetch/bzrurl.py
@@ -1,78 +1,76 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import os
+from subprocess import check_call
 from charmhelpers.fetch import (
     BaseFetchHandler,
-    UnhandledSource
+    UnhandledSource,
+    filter_installed_packages,
+    install,
 )
 from charmhelpers.core.host import mkdir
 
-import six
-if six.PY3:
-    raise ImportError('bzrlib does not support Python3')
 
-try:
-    from bzrlib.branch import Branch
-    from bzrlib import bzrdir, workingtree, errors
-except ImportError:
-    from charmhelpers.fetch import apt_install
-    apt_install("python-bzrlib")
-    from bzrlib.branch import Branch
-    from bzrlib import bzrdir, workingtree, errors
+if filter_installed_packages(['bzr']) != []:
+    install(['bzr'])
+    if filter_installed_packages(['bzr']) != []:
+        raise NotImplementedError('Unable to install bzr')
 
 
 class BzrUrlFetchHandler(BaseFetchHandler):
-    """Handler for bazaar branches via generic and lp URLs"""
+    """Handler for bazaar branches via generic and lp URLs."""
+
     def can_handle(self, source):
         url_parts = self.parse_url(source)
-        if url_parts.scheme not in ('bzr+ssh', 'lp'):
+        if url_parts.scheme not in ('bzr+ssh', 'lp', ''):
             return False
+        elif not url_parts.scheme:
+            return os.path.exists(os.path.join(source, '.bzr'))
         else:
             return True
 
-    def branch(self, source, dest):
-        url_parts = self.parse_url(source)
-        # If we use lp:branchname scheme we need to load plugins
+    def branch(self, source, dest, revno=None):
         if not self.can_handle(source):
             raise UnhandledSource("Cannot handle {}".format(source))
-        if url_parts.scheme == "lp":
-            from bzrlib.plugin import load_plugins
-            load_plugins()
-        try:
-            local_branch = bzrdir.BzrDir.create_branch_convenience(dest)
-        except errors.AlreadyControlDirError:
-            local_branch = Branch.open(dest)
-        try:
-            remote_branch = Branch.open(source)
-            remote_branch.push(local_branch)
-            tree = workingtree.WorkingTree.open(dest)
-            tree.update()
-        except Exception as e:
-            raise e
+        cmd_opts = []
+        if revno:
+            cmd_opts += ['-r', str(revno)]
+        if os.path.exists(dest):
+            cmd = ['bzr', 'pull']
+            cmd += cmd_opts
+            cmd += ['--overwrite', '-d', dest, source]
+        else:
+            cmd = ['bzr', 'branch']
+            cmd += cmd_opts
+            cmd += [source, dest]
+        check_call(cmd)
 
-    def install(self, source):
+    def install(self, source, dest=None, revno=None):
         url_parts = self.parse_url(source)
         branch_name = url_parts.path.strip("/").split("/")[-1]
-        dest_dir = os.path.join(os.environ.get('CHARM_DIR'), "fetched",
-                                branch_name)
-        if not os.path.exists(dest_dir):
-            mkdir(dest_dir, perms=0o755)
+        if dest:
+            dest_dir = os.path.join(dest, branch_name)
+        else:
+            dest_dir = os.path.join(os.environ.get('CHARM_DIR'), "fetched",
+                                    branch_name)
+
+        if dest and not os.path.exists(dest):
+            mkdir(dest, perms=0o755)
+
         try:
-            self.branch(source, dest_dir)
+            self.branch(source, dest_dir, revno)
         except OSError as e:
             raise UnhandledSource(e.strerror)
         return dest_dir
diff --git a/hooks/charmhelpers/fetch/centos.py b/hooks/charmhelpers/fetch/centos.py
new file mode 100644
index 0000000..604bbfb
--- /dev/null
+++ b/hooks/charmhelpers/fetch/centos.py
@@ -0,0 +1,171 @@
+# Copyright 2014-2015 Canonical Limited.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import subprocess
+import os
+import time
+import six
+import yum
+
+from tempfile import NamedTemporaryFile
+from charmhelpers.core.hookenv import log
+
+YUM_NO_LOCK = 1  # The return code for "couldn't acquire lock" in YUM.
+YUM_NO_LOCK_RETRY_DELAY = 10  # Wait 10 seconds between apt lock checks.
+YUM_NO_LOCK_RETRY_COUNT = 30  # Retry to acquire the lock X times.
+
+
+def filter_installed_packages(packages):
+    """Return a list of packages that require installation."""
+    yb = yum.YumBase()
+    package_list = yb.doPackageLists()
+    temp_cache = {p.base_package_name: 1 for p in package_list['installed']}
+
+    _pkgs = [p for p in packages if not temp_cache.get(p, False)]
+    return _pkgs
+
+
+def install(packages, options=None, fatal=False):
+    """Install one or more packages."""
+    cmd = ['yum', '--assumeyes']
+    if options is not None:
+        cmd.extend(options)
+    cmd.append('install')
+    if isinstance(packages, six.string_types):
+        cmd.append(packages)
+    else:
+        cmd.extend(packages)
+    log("Installing {} with options: {}".format(packages,
+                                                options))
+    _run_yum_command(cmd, fatal)
+
+
+def upgrade(options=None, fatal=False, dist=False):
+    """Upgrade all packages."""
+    cmd = ['yum', '--assumeyes']
+    if options is not None:
+        cmd.extend(options)
+    cmd.append('upgrade')
+    log("Upgrading with options: {}".format(options))
+    _run_yum_command(cmd, fatal)
+
+
+def update(fatal=False):
+    """Update local yum cache."""
+    cmd = ['yum', '--assumeyes', 'update']
+    log("Update with fatal: {}".format(fatal))
+    _run_yum_command(cmd, fatal)
+
+
+def purge(packages, fatal=False):
+    """Purge one or more packages."""
+    cmd = ['yum', '--assumeyes', 'remove']
+    if isinstance(packages, six.string_types):
+        cmd.append(packages)
+    else:
+        cmd.extend(packages)
+    log("Purging {}".format(packages))
+    _run_yum_command(cmd, fatal)
+
+
+def yum_search(packages):
+    """Search for a package."""
+    output = {}
+    cmd = ['yum', 'search']
+    if isinstance(packages, six.string_types):
+        cmd.append(packages)
+    else:
+        cmd.extend(packages)
+    log("Searching for {}".format(packages))
+    result = subprocess.check_output(cmd)
+    for package in list(packages):
+        output[package] = package in result
+    return output
+
+
+def add_source(source, key=None):
+    """Add a package source to this system.
+
+    @param source: a URL with a rpm package
+
+    @param key: A key to be added to the system's keyring and used
+    to verify the signatures on packages. Ideally, this should be an
+    ASCII format GPG public key including the block headers. A GPG key
+    id may also be used, but be aware that only insecure protocols are
+    available to retrieve the actual public key from a public keyserver
+    placing your Juju environment at risk.
+    """
+    if source is None:
+        log('Source is not present. Skipping')
+        return
+
+    if source.startswith('http'):
+        directory = '/etc/yum.repos.d/'
+        for filename in os.listdir(directory):
+            with open(directory + filename, 'r') as rpm_file:
+                if source in rpm_file.read():
+                    break
+        else:
+            log("Add source: {!r}".format(source))
+            # write in the charms.repo
+            with open(directory + 'Charms.repo', 'a') as rpm_file:
+                rpm_file.write('[%s]\n' % source[7:].replace('/', '_'))
+                rpm_file.write('name=%s\n' % source[7:])
+                rpm_file.write('baseurl=%s\n\n' % source)
+    else:
+        log("Unknown source: {!r}".format(source))
+
+    if key:
+        if '-----BEGIN PGP PUBLIC KEY BLOCK-----' in key:
+            with NamedTemporaryFile('w+') as key_file:
+                key_file.write(key)
+                key_file.flush()
+                key_file.seek(0)
+            subprocess.check_call(['rpm', '--import', key_file])
+        else:
+            subprocess.check_call(['rpm', '--import', key])
+
+
+def _run_yum_command(cmd, fatal=False):
+    """Run an YUM command.
+
+    Checks the output and retry if the fatal flag is set to True.
+
+    :param: cmd: str: The yum command to run.
+    :param: fatal: bool: Whether the command's output should be checked and
+        retried.
+    """
+    env = os.environ.copy()
+
+    if fatal:
+        retry_count = 0
+        result = None
+
+        # If the command is considered "fatal", we need to retry if the yum
+        # lock was not acquired.
+
+        while result is None or result == YUM_NO_LOCK:
+            try:
+                result = subprocess.check_call(cmd, env=env)
+            except subprocess.CalledProcessError as e:
+                retry_count = retry_count + 1
+                if retry_count > YUM_NO_LOCK_RETRY_COUNT:
+                    raise
+                result = e.returncode
+                log("Couldn't acquire YUM lock. Will retry in {} seconds."
+                    "".format(YUM_NO_LOCK_RETRY_DELAY))
+                time.sleep(YUM_NO_LOCK_RETRY_DELAY)
+
+    else:
+        subprocess.call(cmd, env=env)
diff --git a/hooks/charmhelpers/fetch/giturl.py b/hooks/charmhelpers/fetch/giturl.py
index f023b26..4cf21bc 100644
--- a/hooks/charmhelpers/fetch/giturl.py
+++ b/hooks/charmhelpers/fetch/giturl.py
@@ -1,58 +1,56 @@
 # Copyright 2014-2015 Canonical Limited.
 #
-# This file is part of charm-helpers.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# charm-helpers is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Lesser General Public License version 3 as
-# published by the Free Software Foundation.
+#  http://www.apache.org/licenses/LICENSE-2.0
 #
-# charm-helpers is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import os
+from subprocess import check_call, CalledProcessError
 from charmhelpers.fetch import (
     BaseFetchHandler,
-    UnhandledSource
+    UnhandledSource,
+    filter_installed_packages,
+    install,
 )
-from charmhelpers.core.host import mkdir
-
-import six
-if six.PY3:
-    raise ImportError('GitPython does not support Python 3')
 
-try:
-    from git import Repo
-except ImportError:
-    from charmhelpers.fetch import apt_install
-    apt_install("python-git")
-    from git import Repo
-
-from git.exc import GitCommandError  # noqa E402
+if filter_installed_packages(['git']) != []:
+    install(['git'])
+    if filter_installed_packages(['git']) != []:
+        raise NotImplementedError('Unable to install git')
 
 
 class GitUrlFetchHandler(BaseFetchHandler):
-    """Handler for git branches via generic and github URLs"""
+    """Handler for git branches via generic and github URLs."""
+
     def can_handle(self, source):
         url_parts = self.parse_url(source)
         # TODO (mattyw) no support for ssh git@ yet
-        if url_parts.scheme not in ('http', 'https', 'git'):
+        if url_parts.scheme not in ('http', 'https', 'git', ''):
             return False
+        elif not url_parts.scheme:
+            return os.path.exists(os.path.join(source, '.git'))
         else:
             return True
 
-    def clone(self, source, dest, branch, depth=None):
+    def clone(self, source, dest, branch="master", depth=None):
         if not self.can_handle(source):
             raise UnhandledSource("Cannot handle {}".format(source))
 
-        if depth:
-            Repo.clone_from(source, dest, branch=branch, depth=depth)
+        if os.path.exists(dest):
+            cmd = ['git', '-C', dest, 'pull', source, branch]
         else:
-            Repo.clone_from(source, dest, branch=branch)
+            cmd = ['git', 'clone', source, dest, '--branch', branch]
+            if depth:
+                cmd.extend(['--depth', depth])
+        check_call(cmd)
 
     def install(self, source, branch="master", dest=None, depth=None):
         url_parts = self.parse_url(source)
@@ -62,11 +60,9 @@ class GitUrlFetchHandler(BaseFetchHandler):
         else:
             dest_dir = os.path.join(os.environ.get('CHARM_DIR'), "fetched",
                                     branch_name)
-        if not os.path.exists(dest_dir):
-            mkdir(dest_dir, perms=0o755)
         try:
             self.clone(source, dest_dir, branch, depth)
-        except GitCommandError as e:
+        except CalledProcessError as e:
             raise UnhandledSource(e)
         except OSError as e:
             raise UnhandledSource(e.strerror)
diff --git a/hooks/charmhelpers/fetch/ubuntu.py b/hooks/charmhelpers/fetch/ubuntu.py
new file mode 100644
index 0000000..fce496b
--- /dev/null
+++ b/hooks/charmhelpers/fetch/ubuntu.py
@@ -0,0 +1,336 @@
+# Copyright 2014-2015 Canonical Limited.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import six
+import time
+import subprocess
+
+from tempfile import NamedTemporaryFile
+from charmhelpers.core.host import (
+    lsb_release
+)
+from charmhelpers.core.hookenv import log
+from charmhelpers.fetch import SourceConfigError
+
+CLOUD_ARCHIVE = """# Ubuntu Cloud Archive
+deb http://ubuntu-cloud.archive.canonical.com/ubuntu {} main
+"""
+
+PROPOSED_POCKET = """# Proposed
+deb http://archive.ubuntu.com/ubuntu {}-proposed main universe multiverse restricted
+"""
+
+CLOUD_ARCHIVE_POCKETS = {
+    # Folsom
+    'folsom': 'precise-updates/folsom',
+    'precise-folsom': 'precise-updates/folsom',
+    'precise-folsom/updates': 'precise-updates/folsom',
+    'precise-updates/folsom': 'precise-updates/folsom',
+    'folsom/proposed': 'precise-proposed/folsom',
+    'precise-folsom/proposed': 'precise-proposed/folsom',
+    'precise-proposed/folsom': 'precise-proposed/folsom',
+    # Grizzly
+    'grizzly': 'precise-updates/grizzly',
+    'precise-grizzly': 'precise-updates/grizzly',
+    'precise-grizzly/updates': 'precise-updates/grizzly',
+    'precise-updates/grizzly': 'precise-updates/grizzly',
+    'grizzly/proposed': 'precise-proposed/grizzly',
+    'precise-grizzly/proposed': 'precise-proposed/grizzly',
+    'precise-proposed/grizzly': 'precise-proposed/grizzly',
+    # Havana
+    'havana': 'precise-updates/havana',
+    'precise-havana': 'precise-updates/havana',
+    'precise-havana/updates': 'precise-updates/havana',
+    'precise-updates/havana': 'precise-updates/havana',
+    'havana/proposed': 'precise-proposed/havana',
+    'precise-havana/proposed': 'precise-proposed/havana',
+    'precise-proposed/havana': 'precise-proposed/havana',
+    # Icehouse
+    'icehouse': 'precise-updates/icehouse',
+    'precise-icehouse': 'precise-updates/icehouse',
+    'precise-icehouse/updates': 'precise-updates/icehouse',
+    'precise-updates/icehouse': 'precise-updates/icehouse',
+    'icehouse/proposed': 'precise-proposed/icehouse',
+    'precise-icehouse/proposed': 'precise-proposed/icehouse',
+    'precise-proposed/icehouse': 'precise-proposed/icehouse',
+    # Juno
+    'juno': 'trusty-updates/juno',
+    'trusty-juno': 'trusty-updates/juno',
+    'trusty-juno/updates': 'trusty-updates/juno',
+    'trusty-updates/juno': 'trusty-updates/juno',
+    'juno/proposed': 'trusty-proposed/juno',
+    'trusty-juno/proposed': 'trusty-proposed/juno',
+    'trusty-proposed/juno': 'trusty-proposed/juno',
+    # Kilo
+    'kilo': 'trusty-updates/kilo',
+    'trusty-kilo': 'trusty-updates/kilo',
+    'trusty-kilo/updates': 'trusty-updates/kilo',
+    'trusty-updates/kilo': 'trusty-updates/kilo',
+    'kilo/proposed': 'trusty-proposed/kilo',
+    'trusty-kilo/proposed': 'trusty-proposed/kilo',
+    'trusty-proposed/kilo': 'trusty-proposed/kilo',
+    # Liberty
+    'liberty': 'trusty-updates/liberty',
+    'trusty-liberty': 'trusty-updates/liberty',
+    'trusty-liberty/updates': 'trusty-updates/liberty',
+    'trusty-updates/liberty': 'trusty-updates/liberty',
+    'liberty/proposed': 'trusty-proposed/liberty',
+    'trusty-liberty/proposed': 'trusty-proposed/liberty',
+    'trusty-proposed/liberty': 'trusty-proposed/liberty',
+    # Mitaka
+    'mitaka': 'trusty-updates/mitaka',
+    'trusty-mitaka': 'trusty-updates/mitaka',
+    'trusty-mitaka/updates': 'trusty-updates/mitaka',
+    'trusty-updates/mitaka': 'trusty-updates/mitaka',
+    'mitaka/proposed': 'trusty-proposed/mitaka',
+    'trusty-mitaka/proposed': 'trusty-proposed/mitaka',
+    'trusty-proposed/mitaka': 'trusty-proposed/mitaka',
+    # Newton
+    'newton': 'xenial-updates/newton',
+    'xenial-newton': 'xenial-updates/newton',
+    'xenial-newton/updates': 'xenial-updates/newton',
+    'xenial-updates/newton': 'xenial-updates/newton',
+    'newton/proposed': 'xenial-proposed/newton',
+    'xenial-newton/proposed': 'xenial-proposed/newton',
+    'xenial-proposed/newton': 'xenial-proposed/newton',
+}
+
+APT_NO_LOCK = 100  # The return code for "couldn't acquire lock" in APT.
+APT_NO_LOCK_RETRY_DELAY = 10  # Wait 10 seconds between apt lock checks.
+APT_NO_LOCK_RETRY_COUNT = 30  # Retry to acquire the lock X times.
+
+
+def filter_installed_packages(packages):
+    """Return a list of packages that require installation."""
+    cache = apt_cache()
+    _pkgs = []
+    for package in packages:
+        try:
+            p = cache[package]
+            p.current_ver or _pkgs.append(package)
+        except KeyError:
+            log('Package {} has no installation candidate.'.format(package),
+                level='WARNING')
+            _pkgs.append(package)
+    return _pkgs
+
+
+def apt_cache(in_memory=True, progress=None):
+    """Build and return an apt cache."""
+    from apt import apt_pkg
+    apt_pkg.init()
+    if in_memory:
+        apt_pkg.config.set("Dir::Cache::pkgcache", "")
+        apt_pkg.config.set("Dir::Cache::srcpkgcache", "")
+    return apt_pkg.Cache(progress)
+
+
+def install(packages, options=None, fatal=False):
+    """Install one or more packages."""
+    if options is None:
+        options = ['--option=Dpkg::Options::=--force-confold']
+
+    cmd = ['apt-get', '--assume-yes']
+    cmd.extend(options)
+    cmd.append('install')
+    if isinstance(packages, six.string_types):
+        cmd.append(packages)
+    else:
+        cmd.extend(packages)
+    log("Installing {} with options: {}".format(packages,
+                                                options))
+    _run_apt_command(cmd, fatal)
+
+
+def upgrade(options=None, fatal=False, dist=False):
+    """Upgrade all packages."""
+    if options is None:
+        options = ['--option=Dpkg::Options::=--force-confold']
+
+    cmd = ['apt-get', '--assume-yes']
+    cmd.extend(options)
+    if dist:
+        cmd.append('dist-upgrade')
+    else:
+        cmd.append('upgrade')
+    log("Upgrading with options: {}".format(options))
+    _run_apt_command(cmd, fatal)
+
+
+def update(fatal=False):
+    """Update local apt cache."""
+    cmd = ['apt-get', 'update']
+    _run_apt_command(cmd, fatal)
+
+
+def purge(packages, fatal=False):
+    """Purge one or more packages."""
+    cmd = ['apt-get', '--assume-yes', 'purge']
+    if isinstance(packages, six.string_types):
+        cmd.append(packages)
+    else:
+        cmd.extend(packages)
+    log("Purging {}".format(packages))
+    _run_apt_command(cmd, fatal)
+
+
+def apt_mark(packages, mark, fatal=False):
+    """Flag one or more packages using apt-mark."""
+    log("Marking {} as {}".format(packages, mark))
+    cmd = ['apt-mark', mark]
+    if isinstance(packages, six.string_types):
+        cmd.append(packages)
+    else:
+        cmd.extend(packages)
+
+    if fatal:
+        subprocess.check_call(cmd, universal_newlines=True)
+    else:
+        subprocess.call(cmd, universal_newlines=True)
+
+
+def apt_hold(packages, fatal=False):
+    return apt_mark(packages, 'hold', fatal=fatal)
+
+
+def apt_unhold(packages, fatal=False):
+    return apt_mark(packages, 'unhold', fatal=fatal)
+
+
+def add_source(source, key=None):
+    """Add a package source to this system.
+
+    @param source: a URL or sources.list entry, as supported by
+    add-apt-repository(1). Examples::
+
+        ppa:charmers/example
+        deb https://stub:[e-mail]/ubuntu trusty main
+
+    In addition:
+        'proposed:' may be used to enable the standard 'proposed'
+        pocket for the release.
+        'cloud:' may be used to activate official cloud archive pockets,
+        such as 'cloud:icehouse'
+        'distro' may be used as a noop
+
+    @param key: A key to be added to the system's APT keyring and used
+    to verify the signatures on packages. Ideally, this should be an
+    ASCII format GPG public key including the block headers. A GPG key
+    id may also be used, but be aware that only insecure protocols are
+    available to retrieve the actual public key from a public keyserver
+    placing your Juju environment at risk. ppa and cloud archive keys
+    are securely added automtically, so sould not be provided.
+    """
+    if source is None:
+        log('Source is not present. Skipping')
+        return
+
+    if (source.startswith('ppa:') or
+        source.startswith('http') or
+        source.startswith('deb ') or
+            source.startswith('cloud-archive:')):
+        subprocess.check_call(['add-apt-repository', '--yes', source])
+    elif source.startswith('cloud:'):
+        install(filter_installed_packages(['ubuntu-cloud-keyring']),
+                fatal=True)
+        pocket = source.split(':')[-1]
+        if pocket not in CLOUD_ARCHIVE_POCKETS:
+            raise SourceConfigError(
+                'Unsupported cloud: source option %s' %
+                pocket)
+        actual_pocket = CLOUD_ARCHIVE_POCKETS[pocket]
+        with open('/etc/apt/sources.list.d/cloud-archive.list', 'w') as apt:
+            apt.write(CLOUD_ARCHIVE.format(actual_pocket))
+    elif source == 'proposed':
+        release = lsb_release()['DISTRIB_CODENAME']
+        with open('/etc/apt/sources.list.d/proposed.list', 'w') as apt:
+            apt.write(PROPOSED_POCKET.format(release))
+    elif source == 'distro':
+        pass
+    else:
+        log("Unknown source: {!r}".format(source))
+
+    if key:
+        if '-----BEGIN PGP PUBLIC KEY BLOCK-----' in key:
+            with NamedTemporaryFile('w+') as key_file:
+                key_file.write(key)
+                key_file.flush()
+                key_file.seek(0)
+                subprocess.check_call(['apt-key', 'add', '-'], stdin=key_file)
+        else:
+            # Note that hkp: is in no way a secure protocol. Using a
+            # GPG key id is pointless from a security POV unless you
+            # absolutely trust your network and DNS.
+            subprocess.check_call(['apt-key', 'adv', '--keyserver',
+                                   'hkp://keyserver.ubuntu.com:80', '--recv',
+                                   key])
+
+
+def _run_apt_command(cmd, fatal=False):
+    """Run an APT command.
+
+    Checks the output and retries if the fatal flag is set
+    to True.
+
+    :param: cmd: str: The apt command to run.
+    :param: fatal: bool: Whether the command's output should be checked and
+        retried.
+    """
+    env = os.environ.copy()
+
+    if 'DEBIAN_FRONTEND' not in env:
+        env['DEBIAN_FRONTEND'] = 'noninteractive'
+
+    if fatal:
+        retry_count = 0
+        result = None
+
+        # If the command is considered "fatal", we need to retry if the apt
+        # lock was not acquired.
+
+        while result is None or result == APT_NO_LOCK:
+            try:
+                result = subprocess.check_call(cmd, env=env)
+            except subprocess.CalledProcessError as e:
+                retry_count = retry_count + 1
+                if retry_count > APT_NO_LOCK_RETRY_COUNT:
+                    raise
+                result = e.returncode
+                log("Couldn't acquire DPKG lock. Will retry in {} seconds."
+                    "".format(APT_NO_LOCK_RETRY_DELAY))
+                time.sleep(APT_NO_LOCK_RETRY_DELAY)
+
+    else:
+        subprocess.call(cmd, env=env)
+
+
+def get_upstream_version(package):
+    """Determine upstream version based on installed package
+
+    @returns None (if not installed) or the upstream version
+    """
+    import apt_pkg
+    cache = apt_cache()
+    try:
+        pkg = cache[package]
+    except:
+        # the package is unknown to the current apt cache.
+        return None
+
+    if not pkg.current_ver:
+        # package is known, but no version is currently installed.
+        return None
+
+    return apt_pkg.upstream_version(pkg.current_ver.ver_str)
diff --git a/hooks/charmhelpers/osplatform.py b/hooks/charmhelpers/osplatform.py
new file mode 100644
index 0000000..ea490bb
--- /dev/null
+++ b/hooks/charmhelpers/osplatform.py
@@ -0,0 +1,19 @@
+import platform
+
+
+def get_platform():
+    """Return the current OS platform.
+
+    For example: if current os platform is Ubuntu then a string "ubuntu"
+    will be returned (which is the name of the module).
+    This string is used to decide which platform module should be imported.
+    """
+    tuple_platform = platform.linux_distribution()
+    current_platform = tuple_platform[0]
+    if "Ubuntu" in current_platform:
+        return "ubuntu"
+    elif "CentOS" in current_platform:
+        return "centos"
+    else:
+        raise RuntimeError("This module is not supported on {}."
+                           .format(current_platform))
diff --git a/hooks/ntp_hooks.py b/hooks/ntp_hooks.py
index 1faa26d..a385c31 100755
--- a/hooks/ntp_hooks.py
+++ b/hooks/ntp_hooks.py
@@ -91,8 +91,6 @@ def write_config():
     if hookenv.relation_ids('nrpe-external-master'):
         update_nrpe_config()
 
-    hookenv.status_set('active', 'ready')
-
 
 @hooks.hook('nrpe-external-master-relation-joined',
             'nrpe-external-master-relation-changed')
@@ -136,8 +134,19 @@ def update_nrpe_config():
     nrpe_setup.write()
 
 
+def assess_status():
+    hookenv.application_version_set(
+        fetch.get_upstream_version('ntp')
+    )
+    if host.service_running('ntp'):
+        hookenv.status_set('active', 'Unit is ready')
+    else:
+        hookenv.status_set('blocked', 'ntp not running')
+
+
 if __name__ == '__main__':
     try:
         hooks.execute(sys.argv)
     except UnregisteredHookError as e:
         hookenv.log('Unknown hook {} - skipping.'.format(e))
+    assess_status()
diff --git a/hooks/update-status b/hooks/update-status
new file mode 120000
index 0000000..ebfa934
--- /dev/null
+++ b/hooks/update-status
@@ -0,0 +1 @@
+ntp_hooks.py
\ No newline at end of file