how to change the port of a kubernetes container/pod?

Question

I am displaying the output of the "docker ps -a command" to list all the containers to my Html page. I want to change the port of these containers using a button in the page itself. In docker normally if the container is running, I would run a docker stop on the container-id and restart it by adding the -p HOSTPORT:CONTAINERPORT to the command. But since all the containers running are Kubernetes containers/pods, stopping them will re-create a new pod/container with a different name. So how do I change the port of the container/pod in such cases?

output of "docker ps -a command"

 NAMES                              CONTAINER ID  STATUS     
 k8s_nginx_nginx-6cdb6c86d4-z7m7m   56711e6de1be  Up 2 seconds
 k8s_POD_nginx-6cdb6c86d4-z7m7m_d   70b21761cb74  Up 3 seconds
 k8s_coredns_coredns-5c98db65d4-7   dfb21bb7c7f4  Up 7 days
 k8s_POD_coredns-5c98db65d4-7djs8   a336be8230ce  Up 7 days
 k8s_POD_kube-proxy-9722h_kube-sy   5e290420dec4  Up 7 days
 k8s_POD_kube-apiserver-wootz_kub   a23dea72b38b  Exited (255) 7 days ago

nginx.yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  type: NodePort
  ports:
  - name: nginxport
    port: 80
    targetPort: 80
    nodePort: 30000
  selector:
    app: nginx
    tier: frontend

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  selector:
    matchLabels:
      app: nginx
      tier: frontend
  template:
    metadata:
      labels:
        app: nginx
        tier: frontend
    spec:

      containers:
      - image: suji165475/devops-sample:mxgraph
        name: nginx
        ports:
        - containerPort: 80
          name: nginxport

So how can I change the port of any of the containers/pod ?

How are you running the pods? The only way of changing the port is modifying the underlying YAML. Pretty sure that even if you edit the yaml on a running pod, it will re-create it. — SiHa, Aug 27 '19 at 08:12
i am using a yaml file for the nginx pod but the rest of the pods where created automcatically when i installed kubernetes on my machine — Vignesh Swaminathan, Aug 27 '19 at 09:06
there are also a few docker containers which were run through the docker run command — Vignesh Swaminathan, Aug 27 '19 at 09:07
but i want to do this using a button where the user can change the port in the html page itself and restart the container.Its kind of like a container managament panel — Vignesh Swaminathan, Aug 27 '19 at 09:08
Change the port in underlying Deployment ` k8s_nginx_nginx` YAML. — Emruz Hossain, Aug 27 '19 at 10:06
One of the main advantages of kubernetes is to use services, so they take care of containers ip and ports. — EnzoAT_, Aug 27 '19 at 12:11
i know that i can manually change the port in the YAML file itself but i have created a panel(page) where i want to allow the user to change the port of the containers and this input(newly entered) port value should be subsitututed in the YAML files and then have that container automatically restart after this? — Vignesh Swaminathan, Aug 28 '19 at 14:46
if thats not possible can i patch the pod/deployment using kubectl with the new port that the user will input in the panel textbox/inputbox? — Vignesh Swaminathan, Aug 28 '19 at 14:48
As I understand it, you cannot change the port of container. The container will listen to port that the application inside the container is listening. In your Service object you need to specify targetPort equal to that port of your container. — Anatolii Stepaniuk, May 02 '21 at 15:05

score 3 · Answer 1 · answered Aug 27 '19 at 10:56

Most of the attributes of a PodSpec cannot be changed once the pod has been created. The port information is inside the containers array, and the linked documentation explicitly notes that containers "Cannot be updated." You must delete and recreate the pod if you want to change the ports it makes visible (or most of its other properties); there is no other way to do it.

You almost never directly deal with Pods (and for that matter you almost never mix plain Docker containers and Kubernetes on the same host). Typically you create a Deployment object, which can be updated in place, and it takes responsibility for creating and deleting Pods for you.

(The corollary to this is that if you're trying to manually delete and recreate Pods, in isolation, changing their properties, but these Pods are also managed by Deployments or StatefulSets or DaemonSets, the controller will notice that a replica is missing when you delete it and recreate it, with its original settings.)

Sufiyan Parkar · Answer 2 · 2019-08-30T04:28:46.480

1

Answering OP's question, as per his comments.

I want to change the port on which my kubernetes containers run. I want to change the nodeport,container port,targetport for it. so how can do this using kubectl patch command for both the service and deployment?

kubectl patch deployment nginx  --type json   -p='[{"op": "replace", "path": "/spec/template/spec/containers/0/ports/0/containerPort", "new port"}]' && \
kubectl patch service nginx --type json   -p='[{"op": "replace", "path": "/spec/type/spec/ports/0/targetPort", "new port"}]' && \
kubectl patch service nginx --type json   -p='[{"op": "replace", "path": "/spec/type/spec/ports/0/nodePort", "new port"}]'

Here is how to change pod specs,

kubectl patch pod valid-pod --type='json' -p='[{"op": "replace", "path": "/spec/containers/0/ports/0/port", "value":"new port"}]'

As David said, Pods aren't really used directly without a deployment.

What you would normally do, have a deployment with deploys the pods and that configuration can be then edited using kubectl.

Try using something like this,

kubectl patch deployment valid-deployment  --type json   -p='[{"op": "replace", "path": "/spec/template/spec/containers/0/ports/0/port", "new port"}]'

If you patch the deployment, the pods automatically restart.

That being said, if you change the port of the container, the service targetport would have to be changed too. The simple fix for that would to make sure all your container ports have name attribute filled which are mapped to their appropriate k8s services.

edited Aug 30 '19 at 04:28

answered Aug 28 '19 at 11:43

Sufiyan Parkar

167
2
12

can you show to an example of the kubectl patch using that yaml has an example?I have created a container managament panel where the user will change the port and this new port entered by user should be used to patch the deployment. – Vignesh Swaminathan Aug 28 '19 at 14:57
or is there any other way of using this newly entered port to be used in the YAML file? – Vignesh Swaminathan Aug 28 '19 at 14:59
the panel was created using html and node.js(express) – Vignesh Swaminathan Aug 28 '19 at 15:00
https://stackoverflow.com/questions/57657609/how-to-change-the-port-of-a-docker-container-using-a-button?noredirect=1#comment101766566_57657609 – Vignesh Swaminathan Aug 28 '19 at 15:02
i have posted my problem in that link where i have posted all my code .plz help – Vignesh Swaminathan Aug 28 '19 at 15:03
What are you trying to achieve? Change port on container running on Kubernetes? You can change what port the pod is exposing to the k8s service, but what is the docker image exposing on that port? Docker images can be updated on runtime using rolling updates, but the whole answer depends on WHAT EXACTLY, you plan to achieve, end to end. Changing ports isn't exactly sufficient. – Sufiyan Parkar Aug 29 '19 at 11:30
I want to change the port on which my kubernetes containers run – Vignesh Swaminathan Aug 29 '19 at 11:45
lets say there is an nginx container...i want to change the nodeport,container port,targetport for it – Vignesh Swaminathan Aug 29 '19 at 11:46
so how can do this using kubectl patch command for both the service and deployment? – Vignesh Swaminathan Aug 29 '19 at 11:48

how to change the port of a kubernetes container/pod?

2 Answers2