expand install docs how to easily automate strictARP change
Will hopefully save the next person who wants to automate deployment
in an idempotent way some time.
@@ -20,6 +20,8 @@ manifests, or using Kustomize.
If you're using kube-proxy in IPVS mode, since Kubernetes v1.14.2 you have to enable strict ARP mode.
+*Note, you don't need this if you're using kube-router as service-proxy because it is enabling strict arp by default.*
+
You can achieve this by editing kube-proxy config in current cluster:
```shell
@@ -38,7 +40,19 @@ ipvs:
You can also add this configuration snippet to your kubeadm-config, just append it with `---` after the main configuration.
-Note, you don't need this if you're using kube-router as service-proxy because it is enabling strict arp by default.
+If you are trying to automate this change, these shell snippets may help you:
+
+```shell
+# see what changes would be made, returns nonzero returncode if different
+kubectl get configmap kube-proxy -n kube-system -o yaml | \
+sed -e "s/strictARP: false/strictARP: true/" | \
+kubectl diff -f - -n kube-system
+
+# actually apply the changes, returns nonzero returncode on errors only
+kubectl get configmap kube-proxy -n kube-system -o yaml | \
+sed -e "s/strictARP: false/strictARP: true/" | \
+kubectl apply -f - -n kube-system
+```
## Installation by manifest
