Modifying Kernel Parameters Using a Privileged Container

Prerequisites

To access a Kubernetes cluster from a client, you can use the Kubernetes command line tool kubectl.

Procedure

1. Create a DaemonSet on the backend, select the Nginx image, enable the privileged container, configure the lifecycle, and specify hostNetwork: true.
   1. Create a DaemonSet file.

      vi daemonset.yaml

      An example YAML file is provided as follows:

      

      The spec.spec.containers.lifecycle field indicates the command that will be run after the container is started.

      kind: DaemonSet
      apiVersion: apps/v1
      metadata:
        name: daemonset-test
        labels:
          name: daemonset-test
      spec:
        selector:
          matchLabels:
            name: daemonset-test
        template:
          metadata:
            labels:
              name: daemonset-test
          spec:
            hostNetwork: true
            containers:
            - name: daemonset-test
              image: nginx:alpine-perl
              command:
              - "/bin/sh"
              args:
              - "-c"
              - while :; do  time=$(date);done
              imagePullPolicy: IfNotPresent
              lifecycle:
                postStart:
                  exec:
                    command:
                    - sysctl
                    - "-w"
                    - net.ipv4.tcp_tw_reuse=1
              securityContext:
                privileged: true
            imagePullSecrets:
            - name: default-secret

   2. Create the DaemonSet.

      kubectl create –f daemonSet.yaml

2. Check whether the DaemonSet has been created.

   kubectl get daemonset {daemonset_name}

   In this example, run the following command:

   kubectl get daemonset daemonset-test

   Information similar to the following is displayed:

   NAME               DESIRED    CURRENT   READY    UP-T0-DATE    AVAILABLE     NODE SELECTOR   AGE
   daemonset-test     2          2         2        2             2             <node>          2h

3. Obtain the IDs of the DaemonSet pods on the nodes.

   kubectl get pod | grep {daemonset_name}

   In this example, run the following command:

   kubectl get pod | grep daemonset-test

   Information similar to the following is displayed:

   daemonset-test-mqdpv               1/1     Running             0          2h
   daemonset-test-n56vm               1/1     Running             0          2h

4. Access the container.

   kubectl exec -it {pod_name} -- /bin/sh

   In this example, run the following command:

   kubectl exec -it daemonset-test-mqdpv -- /bin/sh

5. Check whether the configured command is executed after the container is started.

   sysctl -a |grep net.ipv4.tcp_tw_reuse

   If the following information is displayed, the system parameters are modified successfully:

   net.ipv4.tcp_tw_reuse=1