---
title: PKI Certificates and Requirements
reviewers:
- sig-cluster-lifecycle 
content_template: templates/concept
---

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Kubernetes requires PKI certificates for authentication over TLS.
If you install Kubernetes with [kubeadm](/docs/reference/setup-tools/kubeadm/kubeadm/), the certificates that your cluster requires are automatically generated.
You can also generate your own certificates -- for example, to keep your private keys more secure by not storing them on the API server.
This page explains the certificates that your cluster requires.

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## How certificates are used by your cluster

Kubernetes requires PKI for the following operations:

* Client certificates for the kubelet to authenticate to the API server
* Server certificate for the API server endpoint
* Client certificates for administrators of the cluster to authenticate to the API server
* Client certificates for the API server to talk to the kubelets
* Client certificate for the API server to talk to etcd
* Client certificate/kubeconfig for the controller manager to talk to the API server
* Client certificate/kubeconfig for the scheduler to talk to the API server.
* Client and server certificates for the [front-proxy][proxy]

{{< note >}}
`front-proxy` certificates are required only if you run kube-proxy to support [an extension API server](/docs/tasks/access-kubernetes-api/setup-extension-api-server/).
{{< /note >}}

etcd also implements mutual TLS to authenticate clients and peers.

## Where certificates are stored

If you install Kubernetes with kubeadm, certificates are stored in `/etc/kubernetes/pki`. All paths in this documentation are relative to that directory.

## Configure certificates manually

If you don't want kubeadm to generate the required certificates, you can create them in either of the following ways.

### Single root CA

You can create a single root CA, controlled by an administrator. This root CA can then create multiple intermediate CAs, and delegate all further creation to Kubernetes itself. 

Required CAs:

| path                   | Default CN                | description                      |
|------------------------|---------------------------|----------------------------------|
| ca.crt,key             | kubernetes-ca             | Kubernetes general CA            |
| etcd/ca.crt,key        | etcd-ca                   | For all etcd-related functions   |
| front-proxy-ca.crt,key | kubernetes-front-proxy-ca | For the [front-end proxy][proxy] |

### All certificates

If you don't wish to copy these private keys to your API servers, you can generate all certificates yourself. 

Required certificates:

| Default CN                    | Parent CA                 | O (in Subject) | kind                                   | hosts (SAN)                                 |
|-------------------------------|---------------------------|----------------|----------------------------------------|---------------------------------------------|
| kube-etcd                     | etcd-ca                   |                | server, client [<sup>1</sup>][etcdbug] | `localhost`, `127.0.0.1`                        |
| kube-etcd-peer                | etcd-ca                   |                | server, client                                   | `<hostname>`, `<Host_IP>`, `localhost`, `127.0.0.1` |
| kube-etcd-healthcheck-client  | etcd-ca                   |                | client                                 |                                             |
| kube-apiserver-etcd-client    | etcd-ca                   | system:masters | client                                 |                                             |
| kube-apiserver                | kubernetes-ca             |                | server                                 | `<hostname>`, `<Host_IP>`, `<advertise_IP>`, `[1]` |
| kube-apiserver-kubelet-client | kubernetes-ca             | system:masters | client                                 |                                             |
| front-proxy-client            | kubernetes-front-proxy-ca |                | client                                 |                                             |

[1]: `kubernetes`, `kubernetes.default`, `kubernetes.default.svc`, `kubernetes.default.svc.cluster`, `kubernetes.default.svc.cluster.local`

where `kind` maps to one or more of the [x509 key usage][usage] types:

| kind   | Key usage                                                                       |
|--------|---------------------------------------------------------------------------------|
| server | digital signature, key encipherment, server auth                                |
| client | digital signature, key encipherment, client auth                                |

### Certificate paths

Certificates should be placed in a recommended path (as used by [kubeadm][kubeadm]). Paths should be specified using the given argument regardless of location.

| Default CN                   | recommend key path           | recommended cert path       | command        | key argument                 | cert argument                             |
|------------------------------|------------------------------|-----------------------------|----------------|------------------------------|-------------------------------------------|
| etcd-ca                      |                              | etcd/ca.crt                 | kube-apiserver |                              | --etcd-cafile                             |
| etcd-client                  | apiserver-etcd-client.key    | apiserver-etcd-client.crt   | kube-apiserver | --etcd-keyfile               | --etcd-certfile                           |
| kubernetes-ca                |                              | ca.crt                      | kube-apiserver |                              | --client-ca-file                          |
| kube-apiserver               | apiserver.key                | apiserver.crt               | kube-apiserver | --tls-private-key-file       | --tls-cert-file                           |
| apiserver-kubelet-client     |                              | apiserver-kubelet-client.crt| kube-apiserver |                              | --kubelet-client-certificate              |
| front-proxy-ca               |                              | front-proxy-ca.crt          | kube-apiserver |                              | --requestheader-client-ca-file            |
| front-proxy-client           | front-proxy-client.key       | front-proxy-client.crt      | kube-apiserver | --proxy-client-key-file      | --proxy-client-cert-file                  |
|                              |                              |                             |                |                              |                                           |
| etcd-ca                      |                              | etcd/ca.crt                 | etcd           |                              | --trusted-ca-file, --peer-trusted-ca-file |
| kube-etcd                    | etcd/server.key              | etcd/server.crt             | etcd           | --key-file                   | --cert-file                               |
| kube-etcd-peer               | etcd/peer.key                | etcd/peer.crt               | etcd           | --peer-key-file              | --peer-cert-file                          |
| etcd-ca                      |                              | etcd/ca.crt                 | etcdctl[2]     |                              | --cacert                                  |
| kube-etcd-healthcheck-client | etcd/healthcheck-client.key  | etcd/healthcheck-client.crt | etcdctl[2]     | --key                        | --cert                                    |

[2]: For a liveness probe, if self-hosted

## Configure certificates for user accounts

You must manually configure these administrator account and service accounts: 

| filename                | credential name            | Default CN                     | O (in Subject) |
|-------------------------|----------------------------|--------------------------------|----------------|
| admin.conf              | default-admin              | kubernetes-admin               | system:masters |
| kubelet.conf            | default-auth               | system:node:`<nodename>`        | system:nodes   |
| controller-manager.conf | default-controller-manager | system:kube-controller-manager |                |
| scheduler.conf          | default-manager            | system:kube-scheduler          |                |

1. For each config, generate an x509 cert/key pair with the given CN and O.

1. Run `kubectl` as follows for each config:

```shell
KUBECONFIG=<filename> kubectl config set-cluster default-cluster --server=https://<host ip>:6443 --certificate-authority <path-to-kubernetes-ca> --embed-certs
KUBECONFIG=<filename> kubectl config set-credentials <credential-name> --client-key <path-to-key>.pem --client-certificate <path-to-cert>.pem --embed-certs
KUBECONFIG=<filename> kubectl config set-context default-system --cluster default-cluster --user <credential-name>
KUBECONFIG=<filename> kubectl config use-context default-system
```

These files are used as follows:

| filename                | command                 | comment                                                               |
|-------------------------|-------------------------|-----------------------------------------------------------------------|
| admin.conf              | kubectl                 | Configures administrator user for the cluster                                      |
| kubelet.conf            | kubelet                 | One required for each node in the cluster.                            |
| controller-manager.conf | kube-controller-manager | Must be added to manifest in `manifests/kube-controller-manager.yaml` |
| scheduler.conf          | kube-scheduler          | Must be added to manifest in `manifests/kube-scheduler.yaml`          |

[usage]: https://godoc.org/k8s.io/api/certificates/v1beta1#KeyUsage
[kubeadm]: /docs/reference/setup-tools/kubeadm/kubeadm/
[proxy]: /docs/tasks/access-kubernetes-api/configure-aggregation-layer/

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