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. For details, see Connecting to a Cluster Using kubectl.

Procedure

1. Create a DaemonSet in the background, select the Nginx image, enable the Privileged Container, configure the lifecycle, and add the hostNetwork field (value: 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 a DaemonSet.

      kubectl create –f daemonSet.yaml

2. Check whether the DaemonSet is successfully 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. Query the container ID of DaemonSet on the node.

   docker ps -a|grep DaemonSet name

   In this example, run the following command:

   docker ps -a|grep daemonset-test

   Information similar to the following is displayed:

   897b99faa9ce        3e094d5696c1                           "/bin/sh  -c while..."     31 minutes ago     Up  30 minutes  ault_fa7cc313-4ac1-11e9-a716-fa163e0aalba_0

4. Access the container.

   docker exec -it containerid /bin/sh

   In this example, run the following command:

   docker exec -it 897b99faa9ce /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