151 lines
4.4 KiB
Markdown
151 lines
4.4 KiB
Markdown
---
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reviewers:
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- caseydavenport
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- danwinship
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title: Declare Network Policy
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min-kubernetes-server-version: v1.8
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content_type: task
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---
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<!-- overview -->
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This document helps you get started using the Kubernetes [NetworkPolicy API](/docs/concepts/services-networking/network-policies/) to declare network policies that govern how pods communicate with each other.
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## {{% heading "prerequisites" %}}
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{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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Make sure you've configured a network provider with network policy support. There are a number of network providers that support NetworkPolicy, including:
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* [Calico](/docs/tasks/administer-cluster/network-policy-provider/calico-network-policy/)
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* [Cilium](/docs/tasks/administer-cluster/network-policy-provider/cilium-network-policy/)
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* [Kube-router](/docs/tasks/administer-cluster/network-policy-provider/kube-router-network-policy/)
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* [Romana](/docs/tasks/administer-cluster/network-policy-provider/romana-network-policy/)
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* [Weave Net](/docs/tasks/administer-cluster/network-policy-provider/weave-network-policy/)
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{{< note >}}
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The above list is sorted alphabetically by product name, not by recommendation or preference. This example is valid for a Kubernetes cluster using any of these providers.
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{{< /note >}}
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<!-- steps -->
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## Create an `nginx` deployment and expose it via a service
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To see how Kubernetes network policy works, start off by creating an `nginx` Deployment.
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```console
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kubectl create deployment nginx --image=nginx
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```
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```none
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deployment.apps/nginx created
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```
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Expose the Deployment through a Service called `nginx`.
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```console
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kubectl expose deployment nginx --port=80
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```
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```none
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service/nginx exposed
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```
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The above commands create a Deployment with an nginx Pod and expose the Deployment through a Service named `nginx`. The `nginx` Pod and Deployment are found in the `default` namespace.
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```console
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kubectl get svc,pod
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```
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```none
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NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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service/kubernetes 10.100.0.1 <none> 443/TCP 46m
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service/nginx 10.100.0.16 <none> 80/TCP 33s
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NAME READY STATUS RESTARTS AGE
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pod/nginx-701339712-e0qfq 1/1 Running 0 35s
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```
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## Test the service by accessing it from another Pod
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You should be able to access the new `nginx` service from other Pods. To access the `nginx` Service from another Pod in the `default` namespace, start a busybox container:
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```console
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kubectl run busybox --rm -ti --image=busybox -- /bin/sh
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```
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In your shell, run the following command:
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```shell
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wget --spider --timeout=1 nginx
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```
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```none
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Connecting to nginx (10.100.0.16:80)
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remote file exists
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```
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## Limit access to the `nginx` service
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To limit the access to the `nginx` service so that only Pods with the label `access: true` can query it, create a NetworkPolicy object as follows:
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{{< codenew file="service/networking/nginx-policy.yaml" >}}
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The name of a NetworkPolicy object must be a valid
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[DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).
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{{< note >}}
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NetworkPolicy includes a `podSelector` which selects the grouping of Pods to which the policy applies. You can see this policy selects Pods with the label `app=nginx`. The label was automatically added to the Pod in the `nginx` Deployment. An empty `podSelector` selects all pods in the namespace.
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{{< /note >}}
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## Assign the policy to the service
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Use kubectl to create a NetworkPolicy from the above `nginx-policy.yaml` file:
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```console
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kubectl apply -f https://k8s.io/examples/service/networking/nginx-policy.yaml
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```
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```none
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networkpolicy.networking.k8s.io/access-nginx created
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```
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## Test access to the service when access label is not defined
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When you attempt to access the `nginx` Service from a Pod without the correct labels, the request times out:
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```console
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kubectl run busybox --rm -ti --image=busybox -- /bin/sh
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```
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In your shell, run the command:
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```shell
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wget --spider --timeout=1 nginx
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```
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```none
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Connecting to nginx (10.100.0.16:80)
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wget: download timed out
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```
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## Define access label and test again
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You can create a Pod with the correct labels to see that the request is allowed:
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```console
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kubectl run busybox --rm -ti --labels="access=true" --image=busybox -- /bin/sh
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```
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In your shell, run the command:
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```shell
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wget --spider --timeout=1 nginx
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```
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```none
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Connecting to nginx (10.100.0.16:80)
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remote file exists
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```
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