Common Kubernetes Operations

As soon as you're connected to your VM, you can interact with the MicroK8s cluster running there by using kubectl CLI. You can find the most common Kubernetes operations below.
Please, pay attention that Kubernetes workloads (Pods, Deployments, Statefulsets, etc.) are distributed between different namespaces. So for every kubectl command related to workloads you should specify the namespace using the -n flag. To list existing namespaces on the Kubernetes cluster, run kubectl get namespaces. Also, you can use --all-namespaces instead of -n <namespace> to apply a command to all namespaces. Ex: kubectl get pods --all-namespaces
Operations with Kubernetes Pod​
Common operations for Pods include get, delete, logs, describe, and exec.
kubectl get pods -n <namespace> - list all Pods in a given namespace
kubectl get pods -o wide -n <namespace> - list all Pods in a given namespace, with more details
kubectl delete pods <pod_name> -n <namespace>- delete a Pod identified by its name. A new Pod will be automatically created by Kubernetes if a corresponding Deployment/StatefulSet/DaemonSet exists
kubectl logs <pod_name> -n <namespace> - dump Pod logs to the stdout
kubectl logs -f <pod_name> -n <namespace> - stream Pod logs to the stdout
kubectl describe pod <pod_name> -n <namespace> - fetch details about Pod.
Output example:
> kubectl describe pod nginx-deployment-67d4bdd6f5-w6kd7 -n core
​
Name:         nginx-deployment-67d4bdd6f5-w6kd7
Namespace:    default
Priority:     0
Node:         kube-worker-1/192.168.0.113
Start Time:   Thu, 17 Feb 2022 16:51:01 -0500
Labels:       app=nginx
              pod-template-hash=67d4bdd6f5
Annotations:  <none>
Status:       Running
IP:           10.88.0.3
IPs:
  IP:           10.88.0.3
  IP:           2001:db8::1
Controlled By:  ReplicaSet/nginx-deployment-67d4bdd6f5
Containers:
  nginx:
    Container ID:   containerd://5403af59a2b46ee5a23fb0ae4b1e077f7ca5c5fb7af16e1ab21c00e0e616462a
    Image:          nginx
    Image ID:       docker.io/library/[email protected]:2834dc507516af02784808c5f48b7cbe38b8ed5d0f4837f16e78d00deb7e7767
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Thu, 17 Feb 2022 16:51:05 -0500
    Ready:          True
    Restart Count:  0
    Limits:
      cpu:     500m
      memory:  128Mi
    Requests:
      cpu:        500m
      memory:     128Mi
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-bgsgp (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
Volumes:
  kube-api-access-bgsgp:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   Guaranteed
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  34s   default-scheduler  Successfully assigned default/nginx-deployment-67d4bdd6f5-w6kd7 to kube-worker-1
  Normal  Pulling    31s   kubelet            Pulling image "nginx"
  Normal  Pulled     30s   kubelet            Successfully pulled image "nginx" in 1.146417389s
  Normal  Created    30s   kubelet            Created container nginx
  Normal  Started    30s   kubelet            Started container nginx
kubectl exec -it finex-55ffdc954d-cslmp -- /bin/bash - execute a command in an interactive shell session on a given Pod If Pod doesn't have bash installed by default (and when you got OCI runtime exec failed: exec failed: container_linux.go:349: starting container process caused "exec: \"bash\": executable file not found in $PATH": unknown running previous command) use sh:
kubectl exec -it finex-55ffdc954d-cslmp -- /bin/sh
Operations with Kubernetes Deployment​
Basic operations to do with Deployment include get, describe, edit and scale.
kubectl get deployments -n <namespace> - list all Deployments in a given namespace
kubectl describe deployment <deployment_name> -n <namespace> - display the detailed state of one or more Deployments
kubectl edit deployment/<deployment_name> -n <namespace> - edit Deployment resource in a text editor. This is equivalent to first get the resource, edit it, and then apply the resource with the updated version
kubectl scale --replicas=3 deployment/mysql -n <namespace> - scale a Deployment named mysql to 3 Pods
Output example of kubectl describe deployment <deployment_name> -n <namespace>:
> kubectl describe deployments nginx-deployment -n core
​
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 30 Nov 2017 10:56:25 +0000
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision=2
Selector:               app=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
   Containers:
    nginx:
      Image:        nginx:1.16.1
      Port:         80/TCP
      Environment:  <none>
      Mounts:       <none>
    Volumes:        <none>
  Conditions:
    Type           Status  Reason
    ----           ------  ------
    Available      True    MinimumReplicasAvailable
    Progressing    True    NewReplicaSetAvailable
  OldReplicaSets:  <none>
  NewReplicaSet:   nginx-deployment-1564180365 (3/3 replicas created)
  Events:
    Type    Reason             Age   From                   Message
    ----    ------             ----  ----                   -------
    Normal  ScalingReplicaSet  2m    deployment-controller  Scaled up replica set nginx-deployment-2035384211 to 3
    Normal  ScalingReplicaSet  24s   deployment-controller  Scaled up replica set nginx-deployment-1564180365 to 1
    Normal  ScalingReplicaSet  22s   deployment-controller  Scaled down replica set nginx-deployment-2035384211 to 2
    Normal  ScalingReplicaSet  22s   deployment-controller  Scaled up replica set nginx-deployment-1564180365 to 2
    Normal  ScalingReplicaSet  19s   deployment-controller  Scaled down replica set nginx-deployment-2035384211 to 1
    Normal  ScalingReplicaSet  19s   deployment-controller  Scaled up replica set nginx-deployment-1564180365 to 3
    Normal  ScalingReplicaSet  14s   deployment-controller  Scaled down replica set nginx-deployment-2035384211 to 0
Operations with Kubernetes Jobs​
A Job creates one or more Pods and will continue to retry execution of the Pods until a specified number of them successfully terminate.
Common operations to do with Jobs include get, describe.
kubectl get jobs -n <namespace> - list all Jobs in a given namespace
kubectl describe jobs <job_name> -n <namespace> - display the detailed state of one or more Jobs
kubectl get jobs/<job_name> -o yaml - return Job definition in yaml format. Can be used to check Job status and history.
kubectl get pods --selector=job-name=<job_name> --output=jsonpath='{.items[*].metadata.name}' - list all Pods related to the given job
To get logs from job related pods:
pods=$(kubectl get pods --selector=job-name=pi --output=jsonpath='{.items[*].metadata.name}' -n <namespaces>)
echo $pods # will list pods which created by the given job
kubectl logs -f $pods -n <namespace> # will show logs for this pods
Output example of kubectl get jobs/<job_name> -o yaml where you can find job status and history:
apiVersion: batch/v1
kind: Job
# .metadata and .spec omitted
status:
  conditions:
  - lastProbeTime: "2021-02-05T13:14:33Z"
    lastTransitionTime: "2021-02-05T13:14:33Z"
    status: "True"
    type: Suspended
  startTime: "2021-02-05T13:13:48Z"
If you have problems with Helm release installation or upgrade related to the hooks/jobs check this doc for troubleshooting instructions​
How to check K8s certificates status
To see certificates and their status in your Kubernetes cluster run:
kubectl get certificate --all-namespaces
To get some additional information about specific certificate run:
kubectl describe certificate <name> -n <namespaces>
Make sure the certificate issue success
1.Check clusterissuer resource
kubectl get clusterissuer -n core
NAME               READY   AGE
letsencrypt-prod   True    7d7h
a. If READY is True continue to the 2nd step.
b. If READY is False we need to re-install clusterissuer and restart the certificate issuing process
kubectl delete clusterissuer letsencrypt-prod -n core
kubectl delete po -l 'app.kubernetes.io/instance=cert-manager' -n core
​
# re-apply clusterissuer
kubectl apply -f /home/ubuntu/resources/clusterissuer.yaml
c. Repeat 1st step.
2.Check certificaterequest resource
kubectl get certificaterequest --all-namespaces
​
NAMESPACE      NAME                      APPROVED   DENIED   READY   ISSUER         REQUESTOR                                 AGE
loading-page   odax-loading-page-n9s9c   True                True    zerossl-prod   system:serviceaccount:core:cert-manager   2d23
If the READY is not True you can run describe command to check the details:
kubectl describe certificaterequest <name> -n <namespace>
3.Check certificate order resource
kubectl get order --all-namespaces
NAMESPACE      NAME                                 STATE   AGE
loading-page   odax-loading-page-n9s9c-2677649829   valid   2d23h
Same as in the previous case, to check details of order if it's not valid:
kubectl describe order <name> -n <namespace>
Validate TLS certificate date and CN/subject
Print out dates of the cert (check if certificate is not expired):
openssl s_client  -connect <domain>:443 -showcerts -servername <domain>  |openssl x509 -noout -dates
Print out the subject/CN of the cert:
openssl s_client  -connect <domain>:443 -showcerts -servername <domain>  |openssl x509 -noout -subject
How to update a Deployment’s image and pull secret using kubectl
To update the image of a Deployment, you can use the command kubectl edit deployment/<deployment_name> -n <namespace> to interactively edit a Deployment, its image is defined by .spec.template.spec.containers[0].image field.
A faster way for that would be:
kubectl set image deployment/<deployment_name> <container_name>=<image> -n <namespace>
<container_name> usually matches the Deployment name, you can get it by running:
kubectl get deployment <deployment_name> -o jsonpath="{.spec.template.spec.containers[*].name} -n <namespace>"
To update secret use:
kubectl edit secrets <secret_name> -n <namespace>
If you'd like to update a specific field inside a Secret's .data key, (be aware that instead of bar you should have base64 encoded data): kubectl get secret <secret_name> -o json -n <namespace> | jq '.data["foo"]="bar"' | kubectl apply -f - After that, you have to delete your pod so changes will apply. To do that, use kubectl delete pod <pod_name> -n <namespace>
Last modified 4mo ago
Common Kubernetes Operations

Operations with Kubernetes Pod​

Operations with Kubernetes Deployment​

Operations with Kubernetes Jobs​

How to check K8s certificates status

Make sure the certificate issue success

Validate TLS certificate date and CN/subject

How to update a Deployment’s image and pull secret using kubectl

Operations with Kubernetes Pod

Operations with Kubernetes Deployment

Operations with Kubernetes Jobs

How to update a Deployment’s image and pull secret using `kubectl`
