Configuring the /etc/hosts File of a Pod Using hostAliases

Application Scenarios

If DNS or other related settings are inappropriate, you can use hostAliases to overwrite the resolution of the hostname at the pod level when adding entries to the /etc/hosts file of the pod.

Procedure

1. Use kubectl to connect to the cluster.
2. Create the hostaliases-pod.yaml file.

   vi hostaliases-pod.yaml

   The field in bold in the YAML file indicates the image name and tag. You can replace the example value as required.

   apiVersion: v1
   kind: Pod
   metadata:
     name: hostaliases-pod
   spec:
     hostAliases:
     - ip: 127.0.0.1
       hostnames:
       - foo.local
       - bar.local
     - ip: 10.1.2.3
       hostnames:
       - foo.remote
       - bar.remote
     containers:
       - name: cat-hosts
         image: tomcat:9-jre11-slim
         lifecycle:
           postStart:
             exec:
               command:
                 - cat
                 - /etc/hosts
     imagePullSecrets:
       - name: default-secret

   Table 1 pod field description

   Parameter	Mandatory	Description
   apiVersion	Yes	API version number
   kind	Yes	Type of the object to be created
   metadata	Yes	Metadata definition of a resource object
   name	Yes	Name of a pod
   spec	Yes	Detailed description of the pod. For details, see Table 2.

   Table 2 spec field description

   Parameter	Mandatory	Description
   hostAliases	Yes	Host alias
   containers	Yes	For details, see Table 3.

   Table 3 containers field description

   Parameter	Mandatory	Description
   name	Yes	Container name
   image	Yes	Container image name
   lifecycle	No	Lifecycle

3. Create a pod.

   kubectl create -f hostaliases-pod.yaml

   If information similar to the following is displayed, the pod is created.

   pod/hostaliases-pod created

4. Query the pod status.

   kubectl get pod hostaliases-pod

   If the pod is in the Running state, the pod is successfully created.

   NAME                  READY          STATUS       RESTARTS      AGE
   hostaliases-pod       1/1            Running      0             16m

5. Check whether the hostAliases functions properly.

   docker ps |grep hostaliases-pod

   docker exec -ti Container ID /bin/sh