Replicaset doesnot update pods in when pod image is modified

Question

I have created a replicaset with wrong container image with below configuration.

apiVersion: extensions/v1beta1
kind: ReplicaSet
metadata:
  name: rs-d33393
  namespace: default
spec:
  replicas: 4
  selector:
    matchLabels:
      name: busybox-pod
  template:
    metadata:
      labels:
        name: busybox-pod
    spec:
      containers:
      - command:
        - sh
        - -c
        - echo Hello Kubernetes! && sleep 3600
        image: busyboxXXXXXXX
        name: busybox-container

Pods Information:

$ kubectl get pods
NAME              READY     STATUS             RESTARTS   AGE
rs-d33393-5hnfx   0/1       InvalidImageName   0          11m
rs-d33393-5rt5m   0/1       InvalidImageName   0          11m
rs-d33393-ngw78   0/1       InvalidImageName   0          11m
rs-d33393-vnpdh   0/1       InvalidImageName   0          11m

After this, i try to edit the image inside replicaset using kubectl edit replicasets.extensions rs-d33393 and update image as busybox.

Now, i am expecting pods to be recreated with proper image as part of replicaset.

This has not been the exact result.

Can someone please explain, why it is so?

Thanks :)

score 13 · Accepted Answer · answered Jan 08 '20 at 09:05

13

With ReplicaSets directly you have to kill the old pod, so the new ones will be created with the right image.

If you would be using a Deployment, and you should, changing the image would force the pod to be re-created.

answered Jan 08 '20 at 09:05

suren

7,817
1
30
51

Shashank V · Answer 2 · 2020-01-08T10:20:44.563

8

Replicaset does not support updates. As long as required number of pods exist matching the selector labels, replicaset's jobs is done. You should use Deployment instead.

https://kubernetes.io/docs/concepts/workloads/controllers/replicaset/

From the docs:

To update Pods to a new spec in a controlled way, use a Deployment, as ReplicaSets do not support a rolling update directly.

edited Jan 08 '20 at 10:20

answered Jan 08 '20 at 09:08

Shashank V

10,007
2
25
41

score 3 · Answer 3 · answered Jan 08 '20 at 10:02

Deployment is a higher-level concept that manages ReplicaSets and provides declarative updates to Pods. Therefore, it is recommend to use Deployments instead of directly using ReplicaSets unless you don’t require updates at all. ( i.e. one may never need to manipulate ReplicaSet objects when using a Deployment)

Its easy to perform rolling updates and rollbacks when deployed using deployments.

$ kubectl create deployment busybox --image=busyboxxxxxxx --dry-run -o yaml > busybox.yaml

$ cat busybox.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: busybox
  name: busybox
spec:
  replicas: 1
  selector:
    matchLabels:
      app: busybox
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: busybox
    spec:
      containers:
      - image: busyboxxxxxxx
        name: busyboxxxxxxx

ubuntu@dlv-k8s-cluster-master:~$ kubectl create -f busybox.yaml --record=true
deployment.apps/busybox created

Check rollout history

ubuntu@dlv-k8s-cluster-master:~$ kubectl rollout history deployment busybox
deployment.apps/busybox
REVISION  CHANGE-CAUSE
1         kubectl create --filename=busybox.yaml --record=true

Update image on deployment

ubuntu@dlv-k8s-cluster-master:~$ kubectl set image deployment.app/busybox *=busybox --record
deployment.apps/busybox image updated


ubuntu@dlv-k8s-cluster-master:~$ kubectl rollout history deployment busybox
deployment.apps/busybox
REVISION  CHANGE-CAUSE
1         kubectl create --filename=busybox.yaml --record=true
2         kubectl set image deployment.app/busybox *=busybox --record=true

Rollback Deployment

ubuntu@dlv-k8s-cluster-master:~$ kubectl rollout undo deployment busybox
deployment.apps/busybox rolled back


ubuntu@dlv-k8s-cluster-master:~$ kubectl rollout history deployment busybox
deployment.apps/busybox
REVISION  CHANGE-CAUSE
2         kubectl set image deployment.app/busybox *=busybox --record=true
3         kubectl create --filename=busybox.yaml --record=true

D.T., thanks for your detailed explanation. I will refer documentation and do some more practise with deployments. — Sravan Kumar, Jan 09 '20 at 02:19

score 2 · Answer 4 · answered Dec 31 '21 at 18:52

2

You could use

k scale rs new-replica-set --replicas=0

and then

k scale rs new-replica-set --replicas=<Your number of replicas>

answered Dec 31 '21 at 18:52

Adouani Riadh

1,162
2
14
37

FenderBender · Answer 5 · 2023-02-09T22:40:12.310

0

Edit the replicaset(assuming its called replicaset.yaml) file with command:

kubectl edit rs replicaset

edit the image name in the editor
save the file
exit the editor

Now , you will need to either delete the replica sets or delete the existing pods:

kubectl delete rs new-replica-set
            
kubectl delete pod pod_1 pod_2 pod_2 pod_4

replicaset should spin up new pods with new image.

edited Feb 09 '23 at 22:40

answered Feb 09 '23 at 22:33

FenderBender

87
1
9

score 0 · Answer 6 · edited Jul 25 '23 at 07:15

0

edit the configuration, set the replica to 0. then use

kubectl replace -f your_definition_file.yml

then again edit the configuration, set the replica to 4, then use

kubectl replace -f your_definition_file.yml

edited Jul 25 '23 at 07:15

Koedlt

4,286
8
15
33

answered Jul 20 '23 at 07:02

Sai Ram Reddy Gosala

1
1

Replicaset doesnot update pods in when pod image is modified

6 Answers6