Add k3s installation

templates/etc/systemd/system/k3s.service.env.j2

@@ -0,0 +1,3 @@
+{% if kubernetes_master|bool %}
+NODE_TOKEN={{ kubernetes_server_token }}
+{% endif %}

templates/etc/systemd/system/k3s.service.j2

@@ -0,0 +1,27 @@
+[Unit]
+Description=Lightweight Kubernetes
+Documentation=https://k3s.io
+After=network-online.target
+
+[Service]
+Type=notify
+EnvironmentFile=/etc/systemd/system/k3s.service.env
+{% if kubernetes_master|bool %}
+ExecStart=/usr/local/bin/k3s server --flannel-backend=wireguard --disable traefik --secrets-encryption
+{% else %}
+ExecStart=/usr/local/bin/k3s agent --server https://{{ kubernetes_master }}:6443 --token ${NODE_TOKEN}
+{% endif %}
+KillMode=process
+Delegate=yes
+# Having non-zero Limit*s causes performance problems due to accounting overhead
+# in the kernel. We recommend using cgroups to do container-local accounting.
+LimitNOFILE=1048576
+LimitNPROC=infinity
+LimitCORE=infinity
+TasksMax=infinity
+TimeoutStartSec=0
+Restart=always
+RestartSec=5s
+
+[Install]
+WantedBy=multi-user.target