diff --git a/example/config.yml b/example/config.yml
index d013ecc..e6e3727 100644
--- a/example/config.yml
+++ b/example/config.yml
@@ -27,8 +27,11 @@ CONTEXT_NAME: "context-{{ CLUSTER_NAME }}"
 K8S_VER: "__k8s_ver__"
 
 # set unique 'k8s_nodename' for each node, if not set(default:'') ip add will be used
+# CAUTION: 'k8s_nodename' must consist of lower case alphanumeric characters, '-' or '.',
+# and must start and end with an alphanumeric character (e.g. 'example.com'),
+# regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*'
 K8S_NODENAME: "{%- if k8s_nodename != '' -%} \
-                    {{ k8s_nodename }} \
+                    {{ k8s_nodename|replace('_', '-')|lower }} \
                {%- else -%} \
                     {{ inventory_hostname }} \
                {%- endif -%}"
diff --git a/example/hosts.allinone b/example/hosts.allinone
index 9713b9c..883a96c 100644
--- a/example/hosts.allinone
+++ b/example/hosts.allinone
@@ -3,10 +3,14 @@
 192.168.1.1
 
 # master node(s), set unique 'k8s_nodename' for each node
+# CAUTION: 'k8s_nodename' must consist of lower case alphanumeric characters, '-' or '.',
+# and must start and end with an alphanumeric character
 [kube_master]
 192.168.1.1 k8s_nodename=''
 
 # work node(s), set unique 'k8s_nodename' for each node
+# CAUTION: 'k8s_nodename' must consist of lower case alphanumeric characters, '-' or '.',
+# and must start and end with an alphanumeric character
 [kube_node]
 192.168.1.1 k8s_nodename=''
 
diff --git a/example/hosts.multi-node b/example/hosts.multi-node
index ad13263..2876750 100644
--- a/example/hosts.multi-node
+++ b/example/hosts.multi-node
@@ -5,14 +5,19 @@
 192.168.1.3
 
 # master node(s), set unique 'k8s_nodename' for each node
+# CAUTION: 'k8s_nodename' must consist of lower case alphanumeric characters, '-' or '.',
+# and must start and end with an alphanumeric character
 [kube_master]
-192.168.1.1 k8s_nodename=''
-192.168.1.2 k8s_nodename=''
+192.168.1.1 k8s_nodename='master-01'
+192.168.1.2 k8s_nodename='master-02'
+192.168.1.3 k8s_nodename='master-03'
 
 # work node(s), set unique 'k8s_nodename' for each node
+# CAUTION: 'k8s_nodename' must consist of lower case alphanumeric characters, '-' or '.',
+# and must start and end with an alphanumeric character
 [kube_node]
-192.168.1.3 k8s_nodename=''
-192.168.1.4 k8s_nodename=''
+192.168.1.4 k8s_nodename='worker-01'
+192.168.1.5 k8s_nodename='worker-02'
 
 # [optional] harbor server, a private docker registry
 # 'NEW_INSTALL': 'true' to install a harbor server; 'false' to integrate with existed one