書名： Learn OpenShift
作者名： Denis Zuev Artemii Kropachev Aleksey Usov
本章字數： 286字
更新時間： 2021-08-13 16:03:52

Exposing Kubernetes services

When we run a pod using the kubectl run command, this pod is accessible only inside Kubernetes. In most of cases, we would want this pod to be accessible from the outside as well. This is where the kubectl expose command comes in handy. Let's create the httpd pod one more time and then expose it to the outside world:

$ kubectl run httpd --image=httpd

$ kubectl get pods
NAME READY STATUS RESTARTS AGE
httpd-66c6df655-8h5f4 1/1 Running 0 27m

Now let's use the kubectl expose command and expose the httpd web server to the outside of Kubernetes:

$ kubectl expose pod httpd-66c6df655-8h5f4 --port=80 --name=httpd-exposed --type=NodePort

While using the kubectl expose command, we specify several options:

port: Pod (Docker container) port that we are going to expose to the outside of the Kubernetes cluster.
name: Kubernetes service name.
type: Kubernetes service type. NodePort uses Kubernetes Node IP.

The command to get a list of exposed Kubernetes services is kubectl get services:

$ kubectl get services
NAME         TYPE     CLUSTER-IP   EXTERNAL-IP   PORT(S)      AGE
kubernetes   ClusterIP 10.96.0.1    <none>     443/TCP         1d
httpd-exposed NodePort 10.110.40.149<none>     80:31395/TCP    3s

Note that port 80 was mapped to dynamic port 31395 on the Minikube VM. The port is dynamically chosen in the range 30000–32767.

Also, there is a ClusterIP field with the IP address 10.110.40.149 allocated for the httpd-expose service. Do not pay attention to this at the moment; we are going to discuss this later in the book.

Finally, use curl to check if the httpd server is available from the outside of the Kubernetes cluster:

$ curl 192.168.99.101:31395
<html><body><h1>It works!</h1></body></html>

If you open this link in your web browser, you should see It works! on the web page.

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Learn OpenShift

Exposing Kubernetes services