Scaling: Manual

The kubectl scale command manually adjusts the number of pod replicas for a Deployment, ReplicaSet, StatefulSet, or Job.

This is useful when you want to:

• Increase replicas to handle more traffic.

• Reduce replicas to save resources.

• Perform manual scaling when Horizontal Pod Autoscaler (HPA) is not required

Basic Syntax Usage

kubectl scale <resource-type> <resource-name> --replicas=<number>

• <resource-type>: Type of resource (e.g., deployment, replicaset, statefulset, job).

• <resource-name>: The name of the resource you want to scale.

• --replicas=<number>: Desired number of pod replicas.

Scaling Deployment

Lets create a deployment using nginx image.

➜ kubectl create deployment my-nginx --image=nginx
deployment.apps/my-nginx created

It will create a deployment with replicas defaulted to 1.

➜ kubectl get deployment my-nginx 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
my-nginx   1/1     1            1           32s

Now lets scale the newly created deployment to 3 replicas using this command below.

➜ kubectl scale deployment my-nginx --replicas=3
deployment.apps/my-nginx scaled

Now if you check teh deployments again, we will have 3 replicas.

➜ kubectl get deployments my-nginx
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
my-nginx   3/3     3            3  

Others

To scale replicaset, statefulset, and job is similar with scaling deployment, we only need to specify the resource type, resource name, and number of replicas in kubectl apply command.

Note that this changes are not persisted. If you have yaml file for your deployment definition you need to change the spec.replicas value.

References

• https://kubernetes.io/docs/reference/kubectl/generated/kubectl_scale/