Creating and Managing Pods

1. Creating Pod from YAML

Example: Basic Pod Definition

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.25
    ports:
    - containerPort: 80

Field	Description	Required
apiVersion	API version to use (v1 for core resources)	Yes
kind	Type of Kubernetes object (Pod)	Yes
metadata.name	Unique name for the Pod	Yes
metadata.labels	Key-value pairs for identifying the Pod	No
spec.containers	List of containers to run in the Pod	Yes
spec.containers.name	Name of the container (within Pod)	Yes
spec.containers.image	Docker image to use for the container	Yes
spec.containers.ports	Port mappings for the container	No

Note: A Pod is the smallest deployable unit in Kubernetes. It can contain one or more containers that share storage and network resources.

2. Running Pod Imperatively

Command	Description	Example
kubectl run	Creates a pod from a container image	`kubectl run nginx --image=nginx:latest`
kubectl run --restart=Never	Creates a pod that does not restart	`kubectl run job-pod --image=busybox --restart=Never`
kubectl run --port	Exposes a port for the pod	`kubectl run web --image=nginx --port=80`

Example: Run a Pod with Environment Variables

kubectl run env-pod --image=nginx --env=ENV=production

Example: Run a Pod with Resource Limits

kubectl run resource-pod --image=nginx --requests.cpu=200m --limits.memory=512Mi

3. Listing Pods

Command	Description	Flags
kubectl get pods	List all pods in the current namespace	`-o wide` to show more details, `--all-namespaces` to list pods across all namespaces
kubectl get pods -A	List all pods in all namespaces	Alias for `--all-namespaces`
kubectl get pods -n <namespace>	List pods in a specific namespace	Use `-n` or `--namespace`
kubectl get pods --show-labels	List pods with their labels	Shows labels for each pod
kubectl get pods -o json	Get pod details in JSON format	Useful for scripting or automation
kubectl get pods -o yaml	Get pod details in YAML format	Useful for configuration or debugging

Example: Listing Pods in a Namespace

kubectl get pods -n production

Example: Listing All Pods with Labels

kubectl get pods --show-labels

Note: By default, kubectl get pods only shows the pod name, status, restart count, and age. Use -o wide for additional details like node name and IP address.

4. Describing Pod Details

Field	Description	Example Value
metadata.name	Name of the Pod	`my-pod`
metadata.namespace	Namespace where the Pod resides	`default`
spec.containers[*].name	Name of the container within the Pod	`nginx`
spec.containers[*].image	Docker image used for the container	`nginx:1.21`
status.phase	Current phase of the Pod lifecycle	`Pending`, `Running`, `Succeeded`, `Failed`
status.podIP	IP address assigned to the Pod	`10.244.0.5`
status.hostIP	IP address of the node where the Pod is scheduled	`192.168.1.100`
status.conditions[*].type	Type of condition (e.g., PodReady, PodScheduled)	`PodReady`
status.conditions[*].status	Status of the condition (True, False, Unknown)	`True`

Example: Describe Pod in YAML

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: default
spec:
  containers:
  - name: nginx
    image: nginx:1.21
    ports:
    - containerPort: 80
status:
  phase: Running
  podIP: 10.244.0.5
  hostIP: 192.168.1.100

Note: The status field is managed by the Kubernetes control plane and should not be manually edited.

5. Viewing Pod Logs

Command	Description	Flags
kubectl logs	Fetches the logs of a pod	`-l` (label selector), `--since`, `--tail`

Example: Fetching logs from a pod

kubectl logs my-pod

Example: Fetching logs with timestamp

kubectl logs my-pod --timestamps=true

Example: Fetching logs from a specific container in a pod

kubectl logs my-pod -c container-name

Note: If a pod has multiple containers, you must specify the container name using -c flag.

Example: Fetching logs for the last hour

kubectl logs my-pod --since=1h

Example: Fetching last 100 lines of logs

kubectl logs my-pod --tail=100

6. Following Log Streams

Command	Description	Options	Example
kubectl logs	Fetches logs from a pod	`-f` to follow log output `-c <container>` to specify container	`kubectl logs -f my-pod`
kubectl logs -p	Fetches logs from a previous instance of a pod	`-f` to follow log output	`kubectl logs -p -f my-pod`

Note: The -f flag allows you to stream logs in real time, useful for debugging live applications.

Warning: Logs may not persist if the pod is deleted or restarted. Ensure log retention policies are in place for production environments.

7. Executing Commands in Pod

Command	Description	Notes
kubectl exec	Execute a command in a pod	Useful for debugging and running one-off tasks
kubectl exec -it	Execute a command in a pod with interactive terminal	Allows for real-time input/output, useful for shell sessions

Example: Executing a command in a pod

kubectl exec -it my-pod -- /bin/sh

Example: Running a command in a specific container

kubectl exec -it my-pod -c container-name -- ls /app

Note: The -it flags are used to allocate a TTY and keep stdin open, which is necessary for interactive commands.

8. Port Forwarding to Pod

Command	Description	Notes
kubectl port-forward	`kubectl port-forward <pod-name> <local-port>:<pod-port>`	Forward local port to a pod's port

Example: Forwarding Local Port to Pod

kubectl port-forward my-pod 8080:80

Note: The command will keep running and forward traffic until terminated.

Warning: Port forwarding is for development/testing only. Not suitable for production use.

9. Deleting Pods

Command	Description	Notes
kubectl delete pod <pod-name>	Delete a specific pod	Immediately terminates the pod
kubectl delete pod -l <label-selector>	Delete pods matching a label selector	Useful for bulk deletion
kubectl delete pod --all	Delete all pods in the namespace	Use with caution

Example: Delete a Pod by Name

kubectl delete pod nginx-deployment-7b4b5c9f8d-xyz12

Example: Delete Pods with Label Selector

kubectl delete pod -l app=nginx

Note: Deleting a pod managed by a controller (like Deployment or StatefulSet) will cause the controller to recreate it.

Warning: Use kubectl delete pod --all carefully as it will remove all pods in the namespace.

10. Using Pod Selectors

Selector Type	Description	Example
labelSelector	Matches pods based on labels	`app=frontend`
fieldSelector	Matches pods based on field values	`status.phase=Running`

Example: Label Selector in Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: frontend-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: frontend
  template:
    metadata:
      labels:
        app: frontend
    spec:
      containers:
      - name: frontend
        image: nginx:latest

Example: Field Selector in Pod List

kubectl get pods -l status.phase=Running

Note: Pod selectors are used in various contexts like Deployment, Service, and ReplicaSet to identify and manage pods.

11. Watching Pod Status

Command	Description	Notes
kubectl get pods	Lists all pods in the current namespace	Default output includes pod name, status, restart count, and age
kubectl get pods -A	Lists all pods across all namespaces	Useful for cluster-wide monitoring
kubectl get pods -w	Watches pods and shows updates in real time	Useful for monitoring pod lifecycle events
kubectl describe pod <pod-name>	Shows detailed information about a specific pod	Includes events, status conditions, and configuration details

Example: Watching Pod Status in Real Time

kubectl get pods -w

Example: Describing a Pod for Detailed Information

kubectl describe pod my-app-pod

Note: The -w flag in kubectl get pods -w enables continuous watching of pod status changes, which is useful for debugging and monitoring.

12. Getting Pod YAML

Command	Description	Example
kubectl get pod <pod-name> -o yaml	Retrieve the full YAML definition of a pod	`kubectl get pod my-pod -o yaml`
kubectl get pod <pod-name> -o json	Retrieve the full JSON definition of a pod	`kubectl get pod my-pod -o json`
kubectl get pod <pod-name> -o yaml --export	Export a pod's definition without status fields	`kubectl get pod my-pod -o yaml --export`

Note: The --export flag removes status and metadata fields, useful for version control or replication.

13. Copying Files to Pod

Command	Description	Example
kubectl cp	Copies files and directories to/from a pod	`kubectl cp /local/path pod-name:/remote/path`

Example: Copying a file to a pod

kubectl cp ./local-file.txt my-pod:/tmp/file.txt

Example: Copying a directory to a pod

kubectl cp ./local-dir my-pod:/tmp/dir

Note: The pod must be running for the copy to succeed.

Warning: kubectl cp uses the pod's internal filesystem and does not support copying to or from containers that are not running.