---
title: Access Clusters Using the Kubernetes API
content_type: task
weight: 60
---

<!-- overview -->
This page shows how to access clusters using the Kubernetes API.

## {{% heading "prerequisites" %}}

{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}

<!-- steps -->

## Accessing the Kubernetes API

### Accessing for the first time with kubectl

When accessing the Kubernetes API for the first time, use the
Kubernetes command-line tool, `kubectl`.

To access a cluster, you need to know the location of the cluster and have credentials
to access it. Typically, this is automatically set-up when you work through
a [Getting started guide](/docs/setup/),
or someone else set up the cluster and provided you with credentials and a location.

Check the location and credentials that kubectl knows about with this command:

```shell
kubectl config view
```

Many of the [examples](https://github.com/kubernetes/examples/tree/master/) provide an introduction to using
kubectl. Complete documentation is found in the [kubectl manual](/docs/reference/kubectl/).

### Directly accessing the REST API

kubectl handles locating and authenticating to the API server. If you want to directly access the REST API with an http client like
`curl` or `wget`, or a browser, there are multiple ways you can locate and authenticate against the API server:

1. Run kubectl in proxy mode (recommended). This method is recommended, since it uses
   the stored API server location and verifies the identity of the API server using a
   self-signed certificate. No man-in-the-middle (MITM) attack is possible using this method.
1. Alternatively, you can provide the location and credentials directly to the http client.
   This works with client code that is confused by proxies. To protect against man in the
   middle attacks, you'll need to import a root cert into your browser.

Using the Go or Python client libraries provides accessing kubectl in proxy mode.

#### Using kubectl proxy

The following command runs kubectl in a mode where it acts as a reverse proxy. It handles
locating the API server and authenticating.

Run it like this:

```shell
kubectl proxy --port=8080 &amp;
```

See [kubectl proxy](/docs/reference/generated/kubectl/kubectl-commands/#proxy) for more details.

Then you can explore the API with curl, wget, or a browser, like so:

```shell
curl http://localhost:8080/api/
```

The output is similar to this:

```json
{
  "versions": [
    "v1"
  ],
  "serverAddressByClientCIDRs": [
    {
      "clientCIDR": "0.0.0.0/0",
      "serverAddress": "10.0.1.149:443"
    }
  ]
}
```

#### Without kubectl proxy

It is possible to avoid using kubectl proxy by passing an authentication token
directly to the API server, like this:

Using `grep/cut` approach:

```shell
# Check all possible clusters, as your .KUBECONFIG may have multiple contexts:
kubectl config view -o jsonpath='{"Cluster name\tServer\n"}{range .clusters[*]}{.name}{"\t"}{.cluster.server}{"\n"}{end}'

# Select name of cluster you want to interact with from above output:
export CLUSTER_NAME="some_server_name"

# Point to the API server referring the cluster name
APISERVER=$(kubectl config view -o jsonpath="{.clusters[?(@.name==\"$CLUSTER_NAME\")].cluster.server}")

# Create a secret to hold a token for the default service account
kubectl apply -f - <<EOF
apiVersion: v1
kind: Secret
metadata:
  name: default-token
  annotations:
    kubernetes.io/service-account.name: default
type: kubernetes.io/service-account-token
EOF

# Wait for the token controller to populate the secret with a token:
while ! kubectl describe secret default-token | grep -E '^token' >/dev/null; do
  echo "waiting for token..." >&amp;2
  sleep 1
done

# Get the token value
TOKEN=$(kubectl get secret default-token -o jsonpath='{.data.token}' | base64 --decode)

# Explore the API with TOKEN
curl -X GET $APISERVER/api --header "Authorization: Bearer $TOKEN" --insecure
```

The output is similar to this:

```json
{
  "kind": "APIVersions",
  "versions": [
    "v1"
  ],
  "serverAddressByClientCIDRs": [
    {
      "clientCIDR": "0.0.0.0/0",
      "serverAddress": "10.0.1.149:443"
    }
  ]
}
```

The above example uses the `--insecure` flag. This leaves it subject to MITM
attacks. When kubectl accesses the cluster it uses a stored root certificate
and client certificates to access the server. (These are installed in the
`~/.kube` directory). Since cluster certificates are typically self-signed, it
may take special configuration to get your http client to use root
certificate.

On some clusters, the API server does not require authentication; it may serve
on localhost, or be protected by a firewall. There is not a standard
for this. [Controlling Access to the Kubernetes API](/docs/concepts/security/controlling-access)
describes how you can configure this as a cluster administrator.

### Programmatic access to the API

Kubernetes officially supports client libraries for [Go](#go-client), [Python](#python-client),
[Java](#java-client), [dotnet](#dotnet-client), [JavaScript](#javascript-client), and
[Haskell](#haskell-client). There are other client libraries that are provided and maintained by
their authors, not the Kubernetes team. See [client libraries](/docs/reference/using-api/client-libraries/)
for accessing the API from other languages and how they authenticate.

#### Go client

* To get the library, run the following command: `go get k8s.io/client-go@kubernetes-<kubernetes-version-number>`
  See [https://github.com/kubernetes/client-go/releases](https://github.com/kubernetes/client-go/releases)
  to see which versions are supported.
* Write an application atop of the client-go clients.

{{< note >}}

`client-go` defines its own API objects, so if needed, import API definitions from client-go rather than
from the main repository. For example, `import "k8s.io/client-go/kubernetes"` is correct.

{{< /note >}}

The Go client can use the same [kubeconfig file](/docs/concepts/configuration/organize-cluster-access-kubeconfig/)
as the kubectl CLI does to locate and authenticate to the API server. See this [example](https://git.k8s.io/client-go/examples/out-of-cluster-client-configuration/main.go):

```golang
package main

import (
  "context"
  "fmt"
  "k8s.io/apimachinery/pkg/apis/meta/v1"
  "k8s.io/client-go/kubernetes"
  "k8s.io/client-go/tools/clientcmd"
)

func main() {
  // uses the current context in kubeconfig
  // path-to-kubeconfig -- for example, /root/.kube/config
  config, _ := clientcmd.BuildConfigFromFlags("", "<path-to-kubeconfig>")
  // creates the clientset
  clientset, _ := kubernetes.NewForConfig(config)
  // access the API to list pods
  pods, _ := clientset.CoreV1().Pods("").List(context.TODO(), v1.ListOptions{})
  fmt.Printf("There are %d pods in the cluster\n", len(pods.Items))
}
```

If the application is deployed as a Pod in the cluster, see
[Accessing the API from within a Pod](/docs/tasks/access-application-cluster/access-cluster/#accessing-the-api-from-a-pod).

#### Python client

To use [Python client](https://github.com/kubernetes-client/python), run the following command:
`pip install kubernetes`. See [Python Client Library page](https://github.com/kubernetes-client/python)
for more installation options.

The Python client can use the same [kubeconfig file](/docs/concepts/configuration/organize-cluster-access-kubeconfig/)
as the kubectl CLI does to locate and authenticate to the API server. See this
[example](https://github.com/kubernetes-client/python/blob/master/examples/out_of_cluster_config.py):

```python
from kubernetes import client, config

config.load_kube_config()

v1=client.CoreV1Api()
print("Listing pods with their IPs:")
ret = v1.list_pod_for_all_namespaces(watch=False)
for i in ret.items:
    print("%s\t%s\t%s" % (i.status.pod_ip, i.metadata.namespace, i.metadata.name))
```

#### Java client

To install the [Java Client](https://github.com/kubernetes-client/java), run:

```shell
# Clone java library
git clone --recursive https://github.com/kubernetes-client/java

# Installing project artifacts, POM etc:
cd java
mvn install
```

See [https://github.com/kubernetes-client/java/releases](https://github.com/kubernetes-client/java/releases)
to see which versions are supported.

The Java client can use the same [kubeconfig file](/docs/concepts/configuration/organize-cluster-access-kubeconfig/)
as the kubectl CLI does to locate and authenticate to the API server. See this
[example](https://github.com/kubernetes-client/java/blob/master/examples/examples-release-15/src/main/java/io/kubernetes/client/examples/KubeConfigFileClientExample.java):

```java
package io.kubernetes.client.examples;

import io.kubernetes.client.ApiClient;
import io.kubernetes.client.ApiException;
import io.kubernetes.client.Configuration;
import io.kubernetes.client.apis.CoreV1Api;
import io.kubernetes.client.models.V1Pod;
import io.kubernetes.client.models.V1PodList;
import io.kubernetes.client.util.ClientBuilder;
import io.kubernetes.client.util.KubeConfig;
import java.io.FileReader;
import java.io.IOException;

/**
 * A simple example of how to use the Java API from an application outside a kubernetes cluster
 *
 * <p>Easiest way to run this: mvn exec:java
 * -Dexec.mainClass="io.kubernetes.client.examples.KubeConfigFileClientExample"
 *
 */
public class KubeConfigFileClientExample {
  public static void main(String[] args) throws IOException, ApiException {

    // file path to your KubeConfig
    String kubeConfigPath = "~/.kube/config";

    // loading the out-of-cluster config, a kubeconfig from file-system
    ApiClient client =
        ClientBuilder.kubeconfig(KubeConfig.loadKubeConfig(new FileReader(kubeConfigPath))).build();

    // set the global default api-client to the in-cluster one from above
    Configuration.setDefaultApiClient(client);

    // the CoreV1Api loads default api-client from global configuration.
    CoreV1Api api = new CoreV1Api();

    // invokes the CoreV1Api client
    V1PodList list = api.listPodForAllNamespaces(null, null, null, null, null, null, null, null, null);
    System.out.println("Listing all pods: ");
    for (V1Pod item : list.getItems()) {
      System.out.println(item.getMetadata().getName());
    }
  }
}
```

#### dotnet client

To use [dotnet client](https://github.com/kubernetes-client/csharp),
run the following command: `dotnet add package KubernetesClient --version 1.6.1`.
See [dotnet Client Library page](https://github.com/kubernetes-client/csharp)
for more installation options. See
[https://github.com/kubernetes-client/csharp/releases](https://github.com/kubernetes-client/csharp/releases)
to see which versions are supported.

The dotnet client can use the same [kubeconfig file](/docs/concepts/configuration/organize-cluster-access-kubeconfig/)
as the kubectl CLI does to locate and authenticate to the API server. See this
[example](https://github.com/kubernetes-client/csharp/blob/master/examples/simple/PodList.cs):

```csharp
using System;
using k8s;

namespace simple
{
    internal class PodList
    {
        private static void Main(string[] args)
        {
            var config = KubernetesClientConfiguration.BuildDefaultConfig();
            IKubernetes client = new Kubernetes(config);
            Console.WriteLine("Starting Request!");

            var list = client.ListNamespacedPod("default");
            foreach (var item in list.Items)
            {
                Console.WriteLine(item.Metadata.Name);
            }
            if (list.Items.Count == 0)
            {
                Console.WriteLine("Empty!");
            }
        }
    }
}
```

#### JavaScript client

To install [JavaScript client](https://github.com/kubernetes-client/javascript),
run the following command: `npm install @kubernetes/client-node`. See
[https://github.com/kubernetes-client/javascript/releases](https://github.com/kubernetes-client/javascript/releases)
to see which versions are supported.

The JavaScript client can use the same [kubeconfig file](/docs/concepts/configuration/organize-cluster-access-kubeconfig/)
as the kubectl CLI does to locate and authenticate to the API server. See this
[example](https://github.com/kubernetes-client/javascript/blob/master/examples/example.js):

```javascript
const k8s = require('@kubernetes/client-node');

const kc = new k8s.KubeConfig();
kc.loadFromDefault();

const k8sApi = kc.makeApiClient(k8s.CoreV1Api);

k8sApi.listNamespacedPod({ namespace: 'default' }).then((res) => {
    console.log(res);
});
```

#### Haskell client

See [https://github.com/kubernetes-client/haskell/releases](https://github.com/kubernetes-client/haskell/releases)
to see which versions are supported.

The [Haskell client](https://github.com/kubernetes-client/haskell) can use the same
[kubeconfig file](/docs/concepts/configuration/organize-cluster-access-kubeconfig/)
as the kubectl CLI does to locate and authenticate to the API server. See this
[example](https://github.com/kubernetes-client/haskell/blob/master/kubernetes-client/example/App.hs):

```haskell
exampleWithKubeConfig :: IO ()
exampleWithKubeConfig = do
    oidcCache <- atomically $ newTVar $ Map.fromList []
    (mgr, kcfg) <- mkKubeClientConfig oidcCache $ KubeConfigFile "/path/to/kubeconfig"
    dispatchMime
            mgr
            kcfg
            (CoreV1.listPodForAllNamespaces (Accept MimeJSON))
        >>= print
```

## {{% heading "whatsnext" %}}

* [Accessing the Kubernetes API from a Pod](/docs/tasks/run-application/access-api-from-pod/)