Add daemonset note from pr-8125

Author: mburke5678

dev_guide/daemonsets.adoc

@@ -19,8 +19,33 @@ A daemonset can be used to run replicas of a pod on specific or all nodes in an
 Use daemonsets to create shared storage, run a logging pod on every node in
 your cluster, or deploy a monitoring agent on every node.
 
+For security reasons, only cluster administrators can create daemonsets. 
+See xref:../admin_guide/manage_rbac.adoc#admin-guide-granting-users-daemonset-permissions[Granting Users Daemonset Permissions].
+
 For more information on daemonsets, see the link:http://kubernetes.io/docs/admin/daemons/[Kubernetes documentation].
 
+[IMPORTANT]
+====
+Daemonset scheduling is incompatible with project's default node selector. If
+you fail to disable it, the daemonset gets restricted by merging with the
+default node selector. This results in frequent pod recreates on the nodes that
+got unselected by the merged node selector, which in turn puts unwanted load on
+the cluster.
+
+Therefore, 
+
+* Before you start using daemonsets, disable the default project-wide xref:../admin_guide/managing_projects.adoc#using-node-selectors[node selector]
+in your namespace, by setting the namespace
+annotation `openshift.io/node-selector` to an empty string:
++
+----
+# oc patch namespace myproject -p \
+    '{"metadata": {"annotations": {"openshift.io/node-selector": ""}}}'
+----
+* If you are creating a new project, overwrite the default node selector using
+`oc adm new-project --node-selector=""`.
+====
+
 [[dev-guide-creating-daemonsets]]
 == Creating Daemonsets