Service: kubectl expose

Another way to create a service is by using kubectl expose command.

kubectl expose <resource-type> <resource-name> --port=<port> --target-port=<target-port> --type=<type>

<resource-type>: Type of Kubernetes resource (pod, deployment, replicaset, etc.).
<resource-name>: Name of the resource to expose.
--port: The external port to expose.
--target-port: The port on the container to forward traffic to.
--type: Type of service (ClusterIP, NodePort, LoadBalancer, or ExternalName).
--name: Name of newly created service.

Expose as ClusterIP Service

First lets create a simple deployment object using nginx image with name my-server.

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

➜ kubectl get deployments.apps                                      
NAME        READY   UP-TO-DATE   AVAILABLE   AGE
my-server   1/1     1            0           10s
postgres    1/1     1            1           25h
simple-go   3/3     3            3           25h

Then lets create a service with type ClusterIP using kubectl exec command. Since ClusterIP is the default type we don't need to specify the --type argument.

➜ kubectl expose deployment my-server --port=80 --target-port=80
service/my-server exposed

➜ kubectl get svc my-server
NAME        TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
my-server   ClusterIP   10.97.240.5   <none>        80/TCP    1m2s

As we can see above the command will create a service name my-server that exposes deployment named my-server. We also can get the details in yaml format using command kubectl get service my-server -o yaml.

apiVersion: v1
kind: Service
metadata:
  creationTimestamp: "2025-02-10T06:03:41Z"
  labels:
    app: my-server
  name: my-server
  namespace: default
  resourceVersion: "129776"
  uid: 618624cb-2f7e-466e-992d-ecfaf400fb72
spec:
  clusterIP: 10.97.240.5
  clusterIPs:
  - 10.97.240.5
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: my-server
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}

Expose as NodePort Service

Lets delete our previous service and then expose our deployment again as NodePort service. We need to delete the previous service because the expose command by default will name the service same as deployment name.

➜ kubectl delete svc my-server 
service "my-server" deleted

Because NodePort is not the default service type, we need to explicitly specify the service type using --type in expose command.

➜ kubectl expose deployment my-server --type=NodePort --port=80 --target-port=80
service/my-server exposed

➜ kubectl get svc my-server 
NAME        TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
my-server   NodePort   10.100.253.32   <none>        80:31775/TCP   8s

Now it exposed as NodePort and you can try to access it using the minikube IP and the service PORT. But if you use minikube on Mac using docker driver like me you will need minikube service to expose it.

Expose as LoadBalancer Service

No lets create another service but with type LoadBalancer. This time we explicitly specify the service name using --name argument.

This command below will create a service with type LoadBalancer and name my-server-lb.

➜ kubectl expose deployment my-server --type=LoadBalancer --name=my-server-lb --port=80 --target-port=80
service/my-server-lb exposed

➜ kubectl get svc my-server-lb 
NAME           TYPE           CLUSTER-IP    EXTERNAL-IP   PORT(S)        AGE
my-server-lb   LoadBalancer   10.96.60.45   <pending>     80:30309/TCP   59s

Run minikube tunnel on the other terminal and test it using curl.

➜ curl http://localhost       

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

Expose Pod Directly

We can also directly expose a pod but this is not recommended in production.

For example lets expose the my-server pod.

➜ kubectl get pods 
NAME                         READY   STATUS    RESTARTS   AGE
my-server-78b5bb4ccc-7cbxf   1/1     Running   0          31m
postgres-f8f589d5b-59rw8     1/1     Running   0          25h
simple-go-5dc4557ffc-c24fp   1/1     Running   0          25h
simple-go-5dc4557ffc-d6tz6   1/1     Running   0          25h
simple-go-5dc4557ffc-gv4fv   1/1     Running   0          25h

➜ kubectl expose pod my-server-78b5bb4ccc-7cbxf --port=80 --target-port=80
service/my-server-78b5bb4ccc-7cbxf exposed

The command above will create a ClusterIP service that expose the pod my-server-78b5bb4ccc-7cbxf.

This is not recommended because as we can see below this service is tied to a specific pod. So if that pod is replaced or upgraded, the service will not work.

➜ kubectl get svc my-server-78b5bb4ccc-7cbxf -o yaml

apiVersion: v1
kind: Service
metadata:
  creationTimestamp: "2025-02-10T06:34:09Z"
  labels:
    app: my-server
    pod-template-hash: 78b5bb4ccc
  name: my-server-78b5bb4ccc-7cbxf
  namespace: default
  resourceVersion: "131264"
  uid: 98ef311b-0054-4023-8d83-ca5b0bc9c025
spec:
  clusterIP: 10.99.77.89
  clusterIPs:
  - 10.99.77.89
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: my-server
    pod-template-hash: 78b5bb4ccc
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}

References

https://kubernetes.io/docs/reference/kubectl/generated/kubectl_expose/

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Last updated 10 months ago