Adapt your Inotify parameters for your Managed Kubernetes Service deployments

Objective

The OVHcloud Managed Kubernetes service gives you access to Kubernetes clusters, without the hassle of installing or operating them. But for some specific usecases, you may have to customize nodes parameters.

This guide will cover the customization of the sysctl parameters which define user limits on the number of inotify resources and inotify file watches.

Requirements

• A Public Cloud project in your OVHcloud account
• An OVHcloud Managed Kubernetes cluster
• Access to your OVHcloud Managed Kubernetes cluster through the Kubeconfig file
• You must have the kubectl command-line tool installed
• Your Kubeconfig is exported into your terminal following this guide : Configuring Kubectl

Instructions

Step 1: Create a privileged DaemonSet and define the value to modify

Create a YAML named sysctl-tuner-daemonset.yaml with the content below:

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: sysctl-tuner
  namespace: kube-system
spec:
  selector:
    matchLabels:
      app: sysctl-tuner
  updateStrategy:
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: sysctl-tuner
    spec:
      hostPID: true
      priorityClassName: system-node-critical
      hostNetwork: true
      tolerations:
        - operator: Exists
      initContainers:
        - image: busybox
          name: sysctl-tuner
          command:
            - sh
            - -c
            - "sysctl -w fs.inotify.max_user_watches=<value> && sysctl -w fs.inotify.max_user_instances=<value>"
          securityContext:
            privileged: true
            runAsUser: 0
      containers:
        - image: registry.k8s.io/pause:3.10
          name: pause

Define the value of the sysctl key fs.inotify.max_user_watches and fs.inotify.max_user_instances based on your applications' needs.

The DaemonSet will set the sysctl parameter fs.inotify.max_user_watches with the value you provided in the DaemonSet configuration on all nodes deployed into your Kubernetes Cluster.

$ kubectl run busybox --image=busybox:latest --rm=true -it --privileged=true -- sysctl -a

Step 2: Test if the changes were applied correctly

In order to check if the inotify value has been changed properly, you can execute a shell into a pod:

$ kubectl exec -it `<pod>` -- cat /proc/sys/fs/inotify/max_user_watches

The output should be the same as the value you defined in the DaemonSet YAML defined above.

Congratulations! You've successfully modified the maximum inotify "max_user_watches" value on your Managed Kubernetes Service.

Go further

To deploy your first application on your Kubernetes cluster, we suggest you refer to our guide to Deploying an application.

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