If the 'docker' group exists, append the 'dd-agent' user to it

recipes/docker.rb

@@ -36,6 +36,12 @@
 #     }
 #   ]
 
+group 'docker' do
+  action :manage
+  append true
+  members 'dd-agent'
+end
+
 datadog_monitor 'docker' do
   init_config node['datadog']['docker']['init_config']
   instances node['datadog']['docker']['instances']

recipes/docker_daemon.rb

@@ -1,3 +1,21 @@
+#
+# Cookbook Name:: datadog
+# Recipe:: docker_daemon
+#
+# Copyright 2011-2016, Datadog
+#
+# 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.
+#
 include_recipe 'datadog::dd-agent'
 
 # Build a data structure with configuration.
@@ -49,6 +67,12 @@
 #     }
 #   ]
 
+group 'docker' do
+  action :manage
+  append true
+  members 'dd-agent'
+end
+
 datadog_monitor 'docker_daemon' do
   init_config node['datadog']['docker_daemon']['init_config']
   instances node['datadog']['docker_daemon']['instances']