> For the complete documentation index, see [llms.txt](https://platform9.com/kb/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://platform9.com/kb/pmk/how-to/how-to-enable-fail-on-swap-false-option-as-a-parameter-value-in.md).

# How To Enable fail-on-swap=false Option as a Parameter Value in Kubelet on a Worker Node

## Problem

How to Enable *fail-on-swap=false* option as a parameter value in Kubelet one a worker node.

## Environment

* Platform9 Managed Kubernetes - All Versions

## Procedure

Steps to enable swap on a worker node.

1. Start kubectl proxy in the background.

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# kubectl proxy --port=8001 &
[1] 22409
root@test-master1:~# Starting to serve on 127.0.0.1:8001
```

{% endtab %}
{% endtabs %}

2. Current Configmap associated with the worker node.

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# kubectl get node 172.20.4.210 -o yaml
...
spec:
configSource:
  configMap:
    kubeletConfigKey: kubelet
name: worker-default-kubelet-config
namespace: kube-system
...
```

{% endtab %}
{% endtabs %}

3. Download and unpackage the worker node configuration.

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# curl -sSL "http://localhost:8001/api/v1/nodes/172.20.4.210/proxy/configz" | jq '.kubeletconfig|.kind="KubeletConfiguration"|.apiVersion="kubelet.config.k8s.io/v1beta1"' > kubelet
```

{% endtab %}
{% endtabs %}

4. Edit the config file named `kubelet` and change the `failSwapOn` parameter value to *false* and saved the file.

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# cat kubelet | grep failSwapOn
  "failSwapOn": false,
```

{% endtab %}
{% endtabs %}

5. Push the config file by creating a new ConfigMap. In this case, the configmap "*new-worker-config-swapon*" is created.

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# kubectl create configmap new-worker-config-swapon -n kube-system --from-file=/root/kubelet
configmap/new-worker-config-swapon created
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# kubectl get configmap -n kube-system | grep swap
new-worker-config-swapon            1      18s
```

{% endtab %}
{% endtabs %}

6. Edit the worker node reference to point to the new ConfigMap.

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# kubectl edit node 172.20.4.210
node/172.20.4.210 edited
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="None" %}

```none
root@test-master1:~# kubectl get node 172.20.4.210 -o yaml
...
spec:
configSource:
  configMap:
    kubeletConfigKey: kubelet
name: new-worker-config-swapon
namespace: kube-system
...
```

{% endtab %}
{% endtabs %}

7. Post this you will observe that the *pf9-kubelet* service on the node will be restarted and a new checkpoint will be created in this case *ca8caeaa-da7d-4d95-8fbb-6adac5795958 (Kubelet always refers to the newest created checkpoint when setting dynamic configuration)*. Note that initially when the service restarts you would see kubelet setting the swap value to "true" from its default configuration in kubelet logs but it will then load the newer configmap and set the value to *false* accordingly.

{% tabs %}
{% tab title="None" %}

```none
ubuntu@test-worker1:/var/log/pf9/kubelet$ less kubelet.INFO
I0111 21:56:30.148885  22192 fsstore.go:116] kubelet config controller: loading Kubelet configuration checkpoint for source /api/v1/namespaces/kube-system/configmaps/new-worker-config-swapon,
UID: ca8caeaa-da7d-4d95-8fbb-6adac5795958, ResourceVersion: 9898516
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="None" %}

```none
root@test-worker1:/var/opt/pf9/kube/kubelet-config/dynamic-config/store/checkpoints# ls -ltr
total 8
drwxr-xr-x 3 pf9 pf9group 4096 Dec 1 23:09 1ed02d48-73e5-448b-8b1e-163a73dac8b0
drwxr-xr-x 3 root root 4096 Jan 11 21:56 ca8caeaa-da7d-4d95-8fbb-6adac5795958

root@juniperlimit-worker1:/var/opt/pf9/kube/kubelet-config/dynamic-config/store/checkpoints/ca8caeaa-da7d-4d95-8fbb-6adac5795958/9898516# cat kubelet | grep -i swap
"failSwapOn": false,
```

{% endtab %}
{% endtabs %}

8. In terms of memory allocation, the node's memory resource request/limit allocation will be honored but since the swap is not supported natively the way in which kubelet does the calculations might not be accurate leading to pod evictions due to memory.

**Note:** If the same change has to be made across all nodes, you can read more about it [here](https://docs.platform9.com/kubernetes/dynamic-kubelet-configuration).

## Additional Information

* Enabling swap on a node in Kubernetes supported starting K8s v1.22. Reference: <https://kubernetes.io/blog/2021/08/04/kubernetes-1-22-release-announcement/#node-system-swap-support>
* From Platform9's perspective, a feature request [PMK8-I-148](https://pf9.aha.io/ideas/ideas/PMK8-I-148) has been created to look into ways and options in which we can expose an option to enable the *fail-on-swap=false* as a feature flag in the cluster creation wizard.


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