--- reviewers: - jsafrane title: Create static Pods weight: 170 content_template: templates/task --- {{% capture overview %}} *Static Pods* are managed directly by the kubelet daemon on a specific node, without the {{< glossary_tooltip text="API server" term_id="kube-apiserver" >}} observing them. Unlike Pods that are managed by the control plane (for example, a {{< glossary_tooltip text="Deployment" term_id="deployment" >}}); instead, the kubelet watches each static Pod (and restarts it if it crashes). Static Pods are always bound to one {{< glossary_tooltip term_id="kubelet" >}} on a specific node. The kubelet automatically tries to create a {{< glossary_tooltip text="mirror Pod" term_id="mirror-pod" >}} on the Kubernetes API server for each static Pod. This means that the Pods running on a node are visible on the API server, but cannot be controlled from there. {{< note >}} If you are running clustered Kubernetes and are using static Pods to run a Pod on every node, you should probably be using a {{< glossary_tooltip text="DaemonSet" term_id="daemonset" >}} instead. {{< /note >}} {{% /capture %}} {{% capture prerequisites %}} {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}} This page assumes you're using {{< glossary_tooltip term_id="docker" >}} to run Pods, and that your nodes are running the Fedora operating system. Instructions for other distributions or Kubernetes installations may vary. {{% /capture %}} {{% capture steps %}} ## Create a static pod {#static-pod-creation} You can configure a static Pod with either a [file system hosted configuration file](/docs/tasks/configure-pod-container/static-pod/#configuration-files) or a [web hosted configuration file](/docs/tasks/configure-pod-container/static-pod/#pods-created-via-http). ### Filesystem-hosted static Pod manifest {#configuration-files} Manifests are standard Pod definitions in JSON or YAML format in a specific directory. Use the `staticPodPath: ` field in the [KubeletConfiguration file](/docs/tasks/administer-cluster/kubelet-config-file), which periodically scans the directory and creates/deletes static Pods as YAML/JSON files appear/disappear there. Note that the kubelet will ignore files starting with dots when scanning the specified directory. For example, this is how to start a simple web server as a static Pod: 1. Choose a node where you want to run the static Pod. In this example, it's `my-node1`. ```shell ssh my-node1 ``` 2. Choose a directory, say `/etc/kubelet.d` and place a web server Pod definition there, e.g. `/etc/kubelet.d/static-web.yaml`: ```shell # Run this command on the node where kubelet is running mkdir /etc/kubelet.d/ cat </etc/kubelet.d/static-web.yaml apiVersion: v1 kind: Pod metadata: name: static-web labels: role: myrole spec: containers: - name: web image: nginx ports: - name: web containerPort: 80 protocol: TCP EOF ``` 3. Configure your kubelet on the node to use this directory by running it with `--pod-manifest-path=/etc/kubelet.d/` argument. On Fedora edit `/etc/kubernetes/kubelet` to include this line: ``` KUBELET_ARGS="--cluster-dns=10.254.0.10 --cluster-domain=kube.local --pod-manifest-path=/etc/kubelet.d/" ``` or add the `staticPodPath: ` field in the [KubeletConfiguration file](/docs/tasks/administer-cluster/kubelet-config-file). 4. Restart the kubelet. On Fedora, you would run: ```shell # Run this command on the node where the kubelet is running systemctl restart kubelet ``` ### Web-hosted static pod manifest {#pods-created-via-http} Kubelet periodically downloads a file specified by `--manifest-url=` argument and interprets it as a JSON/YAML file that contains Pod definitions. Similar to how [filesystem-hosted manifests](#configuration-files) work, the kubelet refetches the manifest on a schedule. If there are changes to the list of static Pods, the kubelet applies them. To use this approach: 1. Create a YAML file and store it on a web server so that you can pass the URL of that file to the kubelet. ```yaml apiVersion: v1 kind: Pod metadata: name: static-web labels: role: myrole spec: containers: - name: web image: nginx ports: - name: web containerPort: 80 protocol: TCP ``` 2. Configure the kubelet on your selected node to use this web manifest by running it with `--manifest-url=`. On Fedora, edit `/etc/kubernetes/kubelet` to include this line: ``` KUBELET_ARGS="--cluster-dns=10.254.0.10 --cluster-domain=kube.local --manifest-url=` ``` 3. Restart the kubelet. On Fedora, you would run: ```shell # Run this command on the node where the kubelet is running systemctl restart kubelet ``` ## Observe static pod behavior {#behavior-of-static-pods} When the kubelet starts, it automatically starts all defined static Pods. As you have defined a static Pod and restarted the kubelet, the new static Pod should already be running. You can view running containers (including static Pods) by running (on the node): ```shell # Run this command on the node where kubelet is running docker ps ``` The output might be something like: ``` CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES f6d05272b57e nginx:latest "nginx" 8 minutes ago Up 8 minutes k8s_web.6f802af4_static-web-fk-node1_default_67e24ed9466ba55986d120c867395f3c_378e5f3c ``` You can see the mirror Pod on the API server: ```shell kubectl get pods ``` ``` NAME READY STATUS RESTARTS AGE static-web-my-node1 1/1 Running 0 2m ``` {{< note >}} Make sure the kubelet has permission to create the mirror Pod in the API server. If not, the creation request is rejected by the API server. See [PodSecurityPolicy](/docs/concepts/policy/pod-security-policy/). {{< /note >}} {{< glossary_tooltip term_id="label" text="Labels" >}} from the static Pod are propagated into the mirror Pod. You can use those labels as normal via {{< glossary_tooltip term_id="selector" text="selectors" >}}, etc. If you try to use `kubectl` to delete the mirror Pod from the API server, the kubelet _doesn't_ remove the static Pod: ```shell kubectl delete pod static-web-my-node1 ``` ``` pod "static-web-my-node1" deleted ``` You can see that the Pod is still running: ```shell kubectl get pods ``` ``` NAME READY STATUS RESTARTS AGE static-web-my-node1 1/1 Running 0 12s ``` Back on your node where the kubelet is running, you can try to stop the Docker container manually. You'll see that, after a time, the kubelet will notice and will restart the Pod automatically: ```shell # Run these commands on the node where the kubelet is running docker stop f6d05272b57e # replace with the ID of your container sleep 20 docker ps ``` ``` CONTAINER ID IMAGE COMMAND CREATED ... 5b920cbaf8b1 nginx:latest "nginx -g 'daemon of 2 seconds ago ... ``` ## Dynamic addition and removal of static pods The running kubelet periodically scans the configured directory (`/etc/kubelet.d` in our example) for changes and adds/removes Pods as files appear/disappear in this directory. ```shell # This assumes you are using filesystem-hosted static Pod configuration # Run these commands on the node where the kubelet is running # mv /etc/kubelet.d/static-web.yaml /tmp sleep 20 docker ps # You see that no nginx container is running mv /tmp/static-web.yaml /etc/kubelet.d/ sleep 20 docker ps ``` ``` CONTAINER ID IMAGE COMMAND CREATED ... e7a62e3427f1 nginx:latest "nginx -g 'daemon of 27 seconds ago ``` {{% /capture %}}