Kubernetes, Docker, and Containerd Frequently Used Commands

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

not

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