Essential Kubernetes Pod Commands and Practical Examples

1. k8s-pod common management commands

Create Pod:

kubectl apply -f pod.yaml
kubectl run nginx --image=nginx

View Pod:

kubectl get pods
kubectl describe pod <PodName>

View logs:

kubectl logs <PodName> [-c CONTAINER]
kubectl logs <PodName> [-c CONTAINER] -f

Enter container terminal: kubectl exec <PodName> [-c CONTAINER] --bash Delete Pod: kubectl delete <PodName> Export pod YAML configuration:

# Example output of `kubectl get pods` and export to YAML
kubectl get pods -o yaml > web-pod.yaml

2. k8s-pod case study

2.1 Implement network sharing

2.1.1 Export configuration file and write case

Write exported web-pod.yaml for testing:

# Sample pod definition
apiVersion: v1
kind: Pod
metadata:
  name: pod-net-test
  namespace: default
spec:
  containers:
  - name: pod-test
    image: busybox
    command: ["/bin/sh"]
    args:
      - "-c"
      - "sleep 3000000"
  - name: web
    image: nginx

2.1.2 Apply configuration file

# kubectl apply -f web-pod.yaml
pod/pod-net-test created

2.1.3 Monitor pod startup

# kubectl get pods
# kubectl get pods -w   (continuous watch)

Note: using -w continuously watches pod status.

2.1.4 Enter pod

# kubectl exec -it pods/pod-net-test -c pod-test -- /bin/sh
Defaulting container name to pod-test.
# ifconfig ... (network info)
# netstat -lntup ... (listening ports)

exec: command to enter container

-it: allocate a pseudo‑terminal

pod-net-test: pod name

-c pod-test: specify container name

-- /bin/sh: shell to run

2.1.5 Verify file is served by nginx

Enter nginx container and modify index.html :

# kubectl exec -it pod-net-test -c web -- /bin/bash
cd /usr/share/nginx/html/
ls
echo 'pod-test' > index.html

Exit nginx, enter busybox and wget the page to verify:

# kubectl exec -it pod-net-test -c pod-test -- /bin/sh
wget http://127.0.0.1:80 -O index.html
cat index.html

Summary:

We verified the nginx service by modifying index.html.

When using kubectl exec, always specify the container with -c.

2.2 Implement shared storage

2.2.1 Export configuration file and write case

Navigate to directory and list files:

# cd /root/yaml/
# ll

Create pod-volume-test.yaml defining a shared emptyDir volume:

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: test
  name: pod-volume-test
  namespace: default
spec:
  containers:
  - image: busybox
    name: test
    command: ["/bin/sh"]
    args:
      - "-c"
      - "sleep 3000000"
    volumeMounts:
    - name: log
      mountPath: /data
  - image: nginx
    name: web
    volumeMounts:
    - name: log
      mountPath: /data
  volumes:
  - name: log
    emptyDir: {}

2.2.2 Create shared directory

# mkdir -p /data

2.2.3 Start service

# kubectl apply -f pod-volume-test.yaml
pod/pod-volume-test created

2.2.4 Verify service started

# kubectl get pods
# (output shows pod-volume-test READY 2/2)

2.2.5 Verify volume sharing

Create index.html in the web container:

# kubectl exec -it pod-volume-test -c web -- /bin/bash
cd /data
touch index.html
echo 'pod volume test' > index.html
ls

Check from the test container that the file is visible:

# kubectl exec -it pod-volume-test -c test -- /bin/sh
cd /data
ls
cat index.html

2.2.6 View logs

View web container logs:

# kubectl logs pod-volume-test -c web -f
... startup logs ...
127.0.0.1 - - [29/Nov/2020:03:51:12 +0000] "GET / HTTP/1.1" 200 612 "-" "Wget" "-"

Access the service from the test container:

# kubectl exec -it pod-volume-test -c test -- /bin/sh
wget http://127.0.0.1 -O index.html
cat index.html

3. k8s-pod field details

# Full YAML pod definition example
apiVersion: v1        # required, version number
kind: Pod             # required, Pod
metadata:
  name: string        # required, pod name
  namespace: string   # required, namespace
  labels: [...]       # custom labels
  annotations: [...]   # custom annotations
spec:
  containers:
  - name: string
    image: string
    imagePullPolicy: [Always|Never|IfNotPresent]
    command: [string]
    args: [string]
    workingDir: string
    volumeMounts:
    - name: string
      mountPath: string
      readOnly: boolean
    ports:
    - name: string
      containerPort: int
      hostPort: int
      protocol: string
    env:
    - name: string
      value: string
    resources:
      limits:
        cpu: string
        memory: string
      requests:
        cpu: string
        memory: string
    livenessProbe:
      exec:
        command: [string]
      httpGet:
        path: string
        port: number
        host: string
        scheme: string
        HttpHeaders:
        - name: string
          value: string
      tcpSocket:
        port: number
      initialDelaySeconds: 0
      timeoutSeconds: 0
      periodSeconds: 0
      successThreshold: 0
      failureThreshold: 0
      securityContext:
        privileged: false
  restartPolicy: [Always|Never|OnFailure]
  nodeSelector: object
  imagePullSecrets:
  - name: string
  hostNetwork: false
  volumes:
  - name: string
    emptyDir: {}
    hostPath: string
      path: string
    secret:
      scretname: string
      items:
      - key: string
        path: string
    configMap:
      name: string
      items:
      - key: string
        path: string