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Basic Commands

kubectl create deployment nginx-depl --image=nginx
deployment.apps/nginx-depl created

kubectl get pod  
NAME                          READY   STATUS    RESTARTS     AGE
nginx-depl-5796b5c499-2rhcn   1/1     Running   1 (6d ago)   9d

# 
kubectl get replicaset
NAME                    DESIRED   CURRENT   READY   AGE
nginx-depl-5796b5c499   1         1         1       9d

kubectl delete deployment nginx-depl              
deployment.apps "nginx-depl" deleted

kubectl create deployment nginx-depl --image=nginx
deployment.apps/nginx-depl created
  1. CRUD commands
kubectl create deployment [name]

kubectl edit deployment [name]

kubectl delete deployment [name]
  1. Status of different K8s components
kubectl get nodes | pod | services | replicaset | deployment

  1. Debugging pods

    1. Logs to console

    bash kubectl logs [pod name]

    1. Get interactive terminal

    ```bash kubectl exec -it [pod name] -- /bin/bash

    kubectl exec -it nginx-depl-85db6bcdc5-c28d8 -- /bin/bash ```

Example

> kubectl create deployment nginx-depl --image=nginx
deployment.apps/nginx-depl created

> kubectl get pods
NAME                          READY   STATUS    RESTARTS   AGE
nginx-depl-85db6bcdc5-c28d8   1/1     Running   0          19s

> kubectl logs nginx-depl-85db6bcdc5-c28d8
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration

> kubectl exec -it nginx-depl-85db6bcdc5-c28d8 -- /bin/bash
root@nginx-depl-85db6bcdc5-c28d8:/# who
root@nginx-depl-85db6bcdc5-c28d8:/# whoami
root

> kubectl get replicaset
NAME                    DESIRED   CURRENT   READY   AGE
nginx-depl-85db6bcdc5   1         1         1       5m51s

> kubectl get deployment
NAME         READY   UP-TO-DATE   AVAILABLE   AGE
nginx-depl   1/1     1            1           6m30s

> kubectl get pod
NAME                          READY   STATUS    RESTARTS        AGE
nginx-depl-85db6bcdc5-c28d8   1/1     Running   1 (4m22s ago)   6m45s

> kubectl delete deployment ngnix-depl
Error from server (NotFound): deployments.apps "ngnix-depl" not found

> kubectl delete deployment ngnix-depl
Error from server (NotFound): deployments.apps "ngnix-depl" not found

> kubectl get deployment              
NAME         READY   UP-TO-DATE   AVAILABLE   AGE
nginx-depl   1/1     1            1           25m

> kubectl delete deployment nginx-depl
deployment.apps "nginx-depl" deleted

Layers of Abstraction

  1. Deployment manages a

    • ReplicaSet

  2. ReplicaSet manages a

    • Pod

  3. Pod is an abstraction of

    • Container
4. Editing a deployment

```bash
kubectl edit deployment nginx-depl

If we edit, the existing pod is terminated and a new pod is created as soon as we save.


### Pod Monitoring

1. Describe a pod

```bash
kubectl describe pod [pod name]

kubectl describe pod nginx-depl-6f7f5bff95-5ttr6
  1. View logs of a pod
kubectl logs [pod name]

kubectl logs nginx-depl-6f7f5bff95-5ttr6

Get Terminal of the Pod

kubectl exec -it nginx-depl-6f7f5bff95-5ttr6 -- /bin/bash

Odyssey > kubectl exec -it nginx-depl-6f7f5bff95-5ttr6 -- /bin/bash root@nginx-depl-6f7f5bff95-5ttr6:/# ls bin dev docker-entrypoint.sh home media opt root sbin sys usr boot docker-entrypoint.d etc lib mnt proc run srv tmp var root@nginx-depl-6f7f5bff95-5ttr6:/#

Get Rid of the Pod

kubectl delete deployment <deployment-name>

Odyssey > kubectl delete deployment nginx-depl
deployment.apps "nginx-depl" deleted

Odyssey > kubectl get pods                    
No resources found in default namespace.

Apply Configuration File

  1. Apply a configuration file
kubectl apply -f nginx-deployment.yaml
deployment.apps/nginx-deployment created
  1. Check the deployment status
kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   1/1     1            1           27s
  1. Edit the configuration file
vi nginx-deployment.yaml
  1. Re-apply the configuration file
kubectl apply -f nginx-deployment.yaml
deployment.apps/nginx-deployment configured
  1. Verify the updated deployment status
kubectl get deployment                
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   2/2     2            2           56s

You can find the nginx-deployment.yaml file in the same directory here.