Kubernetes, Docker, and Containerd Frequently Used Commands

You can manage pods, deployments, and services in Kubernetes cluster, perform image operations with Docker and Containerd. You can view pod logs, update deployments, manage containers, and perform image import/export operations.

Kubernetes

To Check if kubelet is Running

systemctl status kubelet

To See Details on Linux System When There is an Error in kubelet

journalctl -xeu kubelet

To See Details from kubelet When There is an Error in kubelet

kubectl get events --all-namespaces --sort-by='.metadata.creationTimestamp'

To See Logs When There is an Error in a Specific Pod

kubectl logs <POD_NAME> -n <NAMESPACE>

To See Previous Pod's Logs If Pod Was Restarted

kubectl logs --previous <POD_NAME> -n apinizer

To See If Pod Has General Problem

kubectl describe pod <POD_NAME> -n apinizer

To Enter the Relevant Pod When an Operation is Wanted on a Running Pod

kubectl exec -it <POD_NAME> -n prod /bin/bash

Sending Request to a Specific Address Without Entering Pod

kubectl exec -it <POD_NAME> -n prod -- curl x.y.gov.tr

To Restart Pods Under a Deployment

kubectl rollout restart deployment manager -n apinizer

To Scale Pod Count Under a Deployment to Zero

kubectl scale deploy cache -n prod --replicas=0

To Delete a Deployment

kubectl delete -f apinizer-deployment.yaml

To Force Delete If Pod is Stuck in Terminating

kubectl delete pod <POD_NAME> -n apinizer --grace-period=0 --force

To Update Version

After pulling images to servers, the following commands are used. This works like “vi” editor, “:wq” should be used to save and exit.

kubectl edit deployment manager -n apinizer
kubectl edit deployment cache -n prod
kubectl edit deployment worker -n prod

To Clean Pods in Evicted State

kubectl get pod -n prod | grep Evicted | awk '{print $1}' | xargs kubectl delete pod -n prod

Preventing Pod from Running on Specific Nodes Using Kubernetes Node Affinity

affinity:
  nodeAffinity:
    requiredDuringSchedulingIgnoredDuringExecution:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: NotIn
          values:
          - kuberdemo55
          - kuberdemo56

Displaying The Most Frequent Threads

If the Java process is running as PID 1:

kubectl exec -it -n apinizer apimanager-69684b6fd9-5nlhl -- sh -c   'ls /proc/1/task/*/comm 2>/dev/null | xargs cat | sort | uniq -c | sort -rn | head -30'

If the Java PID is not known:

oc exec -n apinizer worker-84f9b77756-wd2n9 -- sh -c 'JPID=$(pgrep -f java | head -1); ls /proc/$JPID/task/*/comm | xargs cat | sort | uniq -c | sort -rn | head -30'

Docker

Listing Images

docker images

Listing All Containers

docker ps -a

Image Pull Operation

sudo docker pull apinizercloud/manager:2024.xx.0

Image Export

sudo docker save apinizercloud/manager:2024.xx.0 > manager_2024.xx.0.tar

Image Import

sudo docker load < manager_2024.xx.0.tar

Containerd

Listing Namespaces

sudo ctr namespaces list

Listing Containers by Namespace

sudo ctr --namespace k8s.io containers ls

Listing Images by Namespace Apinizer Images

sudo ctr -n k8s.io images list | grep apinizer

Image Pull Operation

sudo ctr --namespace k8s.io images pull docker.io/apinizercloud/manager:2024.05.0

Image Export

sudo ctr -n k8s.io images export /tmp/manager:2024.05.0.tar docker.io/apinizercloud/manager:2024.05.0

Image Import

sudo ctr --namespace k8s.io images import /tmp/manager:2024.05.0.tar