Kubernetes - Pods 🐋🐳🐋🐳

Description 👀

A pod is a single instance of an application and is the simplest object you can create in Kubernetes, usually have a 1:1 relationship with containers. Pods can have multiple containers, but they are usually containers of different types that are tightly coupled.

Basic Commands 📝

• get minimal info about pods on cluster

  kubectl get pods
  

• get more info about a pod

  kubectl get pods -o wide
  

• get even more information about a pod

  kubectl describe pod <pod-name>
  

• get pod in yaml format

  kubectl get pod <pod-name> -o yaml
  

• enter a pod

    kubectl exec -it <pod-name> -- /bin/bash
  

• create a pod

  kubectl run <pod-name> --image=<image-name>
  

• edit a pod

  kubectl edit pod <pod-name>
  

• If you are not given a pod definition file, you may extract the definition to a file using the below command, then edit the file to make the necessary changes, delete and re-create the pod.

  kubectl get pod <pod-name> -o yaml > pod-definition.yaml
  

• delete a pod

  kubectl delete pod <pod-name>
  

• view the containers user in a pod

    kubectl exec <pod-name> -- whoami
  

Examples 🧩

• simple pod definition

  apiVersion: v1
  # kind refers to the type of object that will be created
  kind: Pod
  # data about the data that will be created
  metadata:
    name: myapp-pod
    labels:
      app: myapp
      type: testing
  # specification section, providing additional information to Kubernetes about the object
  spec:
    containers:
      - name: nginx-container
        image: nginx
  

• define environment variables for a container

    spec:
      containers:
      - name: <container name>
        image: <image name>
        env:
        - name: DEMO_GREETING
          value: "Hello from the environment"
        - name: DEMO_FAREWELL
          value: "Such a sweet sorrow"
  

• define security context for a container

    spec:
      containers:
      - name: <container name>
        image: <image name>
        securityContext:
          runAsUser: 1000
          capabilities:
            add: ["MAC_ADMIN"]
  

  • capabilties are a set of linux kernel capabilities that can be added to or removed from a container
  • capabilities are only available at the container level, not at the pod level

↩️