Kubernetes – kubectl config – admin configuration

The “kubectl config” config command allows you to do many thing, like setting credentials or changing the context.

You can get, for example, human readable version of the config file right in your console by running:

$ kubectl config view

You get:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://172.17.0.21:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED

As you can see there´s CA certificate.

You can find the same information in full format in the file /etc/kubernetes/admin.conf, whose content is like:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: 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
    server: https://172.17.0.21:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: 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
    client-key-data: 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

Kuberneting – Set, Rollout, apply… update!

The imperative approach allows you to update things faster.

In particular, the following commands:

  • apply
  • scale
  • edit
  • set
  • rollout

APPLY

If you edi the yaml configuration file, you can update your resources by running:

$ kubectl apply -f yourfile.ymal

SCALE

To change the amount of replicas:

$ kubectl scale --replicas 3 deployment webapp

Kubernetes will rearrange the pods immediately. You will see pods being terminated and recreated right away,by running such command.


EDIT

$ kubectl edit deployment/nginx-deployment

SET

The set command is used for frequent little updates.

For example a new imapge version for the pods:

$ kubectl set image deployment <deployment-name> <container-name>=nginx:1.12 --record

If you omit “–record” the change-cause description will not be filled

To set resources:

$ kubectl set resources deployment nginx --limits=cpu=200m,memory=512Mi --requests=cpu=100m,memory=256Mi

This will apply to all the containers.

Set environmental variables in serval ways:
$ kubectl set env deployment nginx --env VAR1=value1
$ kubectl set env deployment nginx --from=configmap/vars --keys="var1,var2"
$ kubectl set env deployment nginx --from=secret/passwords --keys="pass1

Afterwards, check the pods have the environmental variables:
$ kubectl exec -it <podname> bash -- -c "env | grep <varname>"

This will happen to your live resource. After running this command, the image will be updated

ROLLOUT

The kubectl rollout command applies to a deployment. For example, to check the status:

check status:
$ kubectl rollout status deployment/test-deploy

To get the history of the deployment:

$ kubectl rollout history deployment flask

deployments "flask"
REVISION  CHANGE-CAUSE
1         initial deployment
2         kubectl set init container log-sidecar
3         deploying image 0.1.1
4         deploying image 0.2.0

If you annotate your deployment you will see the infomarion in the CHANGE-CAUSE column.

To rollback the deployment to the previous version:

$ kubectl rollout undo deployment/flask

To roll it back to a specific revision:

$ kubectl rollout undo deployment/flask --to-revision=2

Sometimes you don´t want to wait for the deployment to be recreated and you want to trigger it yourself. you can do it like:

$ kubectl rollout restart deploy my-deploy

Kubernetes – Imperative Job creation

Let´s create a job the imperative way, by using the docker whalesay image:

kubectl create job whalesay --image=docker/whalesay --dry-run=client -o yaml > job.yaml -- cowsay I am going to ace CKAD!

We are using the “dry-run” option to create a yaml manifest without creating the job.

In the last part of the command with add a command for the container, that will be put directly in the manifest.

Once the file is created, we can add parameters like completions, parallelism and backoffLimit under the spec.template section, like this:

Then we need to create the job, by running:

kubectl create -f job.yaml -n <your-namespace>

After a while we can see the pods have been run and completed:

If you inspect the log of one of the pod, you can see the funny whale comics:

kubectl logs whalesay-7h27f

MORE ABOUT JOBS

Specifying the restartPolicy is mandatory for a Job.

Notice that:

  • a job is persisted and survives cluster restarts
  • a completed job is kept for tracking purposes
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