Add a note on how to set a hardcoded k3s node name

Fixes #576

Signed-off-by: Dimitris Karakasilis <[email protected]>

docs/content/en/docs/Examples/single-node.md

@@ -35,4 +35,13 @@ k3s:
 Notably:
 
 - We use the `k3s` block to disable `traefik` and `servicelb` (the default `k3s` load balancer).
+- In a single-node setup, you may wish to use a non-generated node name. This can be achieved with these options:
+  ```
+    k3s:
+    enabled: true
+    replace_args: true
+    args:
+    - --node-name=my-node
+  ```
+  (`replace_args` replaces all arguments otherwise passed to k3s by Kairos with those supplied here. Make sure you pass all the arguments you need.)
 - We use `write_files` to write manifests to the default `k3s` manifest directory (`/var/lib/rancher/k3s/server/manifests/`) see [docs](/docs/reference/configuration#kubernetes-manifests) to deploy `MetalLB` and configure it with the `192.168.1.10-192.168.1.20` IP range. Make sure to pick up a range which doesn't interfere with your local DHCP network.