---
reviewers:
- sig-cluster-lifecycle
title: Creating Highly Available Clusters with kubeadm
content_template: templates/task
weight: 50
---

{{% capture overview %}}

This page explains two different approaches to setting up a highly available Kubernetes
cluster using kubeadm:

- With stacked masters. This approach requires less infrastructure. etcd members
and control plane nodes are co-located.
- With an external etcd cluster. This approach requires more infrastructure. The
control plane nodes and etcd members are separated.

Your clusters must run Kubernetes version 1.11 or later. You should also be aware that 
setting up HA clusters with kubeadm is still experimental. You might encounter issues
with upgrading your clusters, for example. We encourage you to try either approach,
and provide feedback.

{{< caution >}}
**Caution**: This page does not address running your cluster on a cloud provider.
In a cloud environment, neither approach documented here works with Service objects
of type LoadBalancer, or with dynamic PersistentVolumes.
{{< /caution >}}

{{% /capture %}}

{{% capture prerequisites %}}

For both methods you need this infrastructure:

- Three machines that meet [kubeadm's minimum
  requirements](/docs/setup/independent/install-kubeadm/#before-you-begin) for
  the masters
- Three machines that meet [kubeadm's minimum
  requirements](/docs/setup/independent/install-kubeadm/#before-you-begin) for
  the workers
- Full network connectivity between all machines in the cluster (public or
  private network is fine)
- SSH access from one device to all nodes in the system
- sudo privileges on all machines

For the external etcd cluster only, you also need:

- Three additional machines for etcd members

{{< note >}}
**Note**: The following examples run Calico as the Pod networking provider. If
you run another networking provider, make sure to replace any default values as
needed.
{{< /note >}}

{{% /capture %}}

{{% capture steps %}}

## First steps for both methods

{{< note >}}
**Note**: All commands in this guide on any control plane or etcd node should be
run as root.
{{< /note >}}

- Find your pod CIDR. For details, see [the CNI network
   documentation](/docs/setup/independent/create-cluster-kubeadm/#pod-network).
   The example uses Calico, so the pod CIDR is `192.168.0.0/16`.

### Configure SSH

1.  Enable ssh-agent on your main device that has access to all other nodes in
    the system:

     ```
     eval $(ssh-agent)
     ```

1.  Add your SSH identity to the session:

     ```
     ssh-add ~/.ssh/path_to_private_key
     ```

1.  SSH between nodes to check that the connection is working correctly.

    - When you SSH to any node, make sure to add the `-A` flag:

      ```
      ssh -A 10.0.0.7
      ```

    - When using sudo on any node, make sure to preserve the environment so SSH
      forwarding works:

      ```
      sudo -E -s
      ```

### Create load balancer for kube-apiserver

{{< note >}}
**Note**: There are many configurations for load balancers. The following
example is only one option. Your cluster requirements may need a
different configuration.
{{< /note >}}

1.  Create a kube-apiserver load balancer with a name that resolves to DNS.

    - In a cloud environment you should place your control plane nodes behind a TCP
      forwarding load balancer. This load balancer distributes traffic to all
      healthy control plane nodes in its target list. The health check for
      an apiserver is a TCP check on the port the kube-apiserver listens on
      (default value `:6443`).

    - It is not recommended to use an IP address directly in a cloud environment.

    - The load balancer must be able to communicate with all control plane nodes
      on the apiserver port. It must also allow incoming traffic on its
      listening port.

1.  Add the first control plane nodes to the load balancer and test the
    connection:

    ```sh
    nc -v LOAD_BALANCER_IP PORT
    ```

    - A connection refused error is expected because the apiserver is not yet
      running. A timeout, however, means the load balancer cannot communicate
      with the control plane node. If a timeout occurs, reconfigure the load
      balancer to communicate with the control plane node.

1.  Add the remaining control plane nodes to the load balancer target group.

## Stacked control plane nodes

### Bootstrap the first stacked control plane node

1.  Create a `kubeadm-config.yaml` template file:

        apiVersion: kubeadm.k8s.io/v1alpha2
        kind: MasterConfiguration
        kubernetesVersion: v1.11.0
        apiServerCertSANs:
        - "LOAD_BALANCER_DNS"
        api:
            controlPlaneEndpoint: "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT"
        etcd:
          local:
            extraArgs:
              listen-client-urls: "https://127.0.0.1:2379,https://CP0_IP:2379"
              advertise-client-urls: "https://CP0_IP:2379"
              listen-peer-urls: "https://CP0_IP:2380"
              initial-advertise-peer-urls: "https://CP0_IP:2380"
              initial-cluster: "CP0_HOSTNAME=https://CP0_IP:2380"
            serverCertSANs:
              - CP0_HOSTNAME
              - CP0_IP
            peerCertSANs:
              - CP0_HOSTNAME
              - CP0_IP
        networking:
            # This CIDR is a Calico default. Substitute or remove for your CNI provider.
            podSubnet: "192.168.0.0/16"


1.  Replace the following variables in the template with the appropriate
    values for your cluster:

    * `LOAD_BALANCER_DNS`
    * `LOAD_BALANCER_PORT`
    * `CP0_HOSTNAME`
    * `CP0_IP`

1.  Run `kubeadm init --config kubeadm-config.yaml`

### Copy required files to other control plane nodes

The following certificates and other required files were created when you ran `kubeadm init`.
Copy these files to your other control plane nodes:

- `/etc/kubernetes/pki/ca.crt`
- `/etc/kubernetes/pki/ca.key`
- `/etc/kubernetes/pki/sa.key`
- `/etc/kubernetes/pki/sa.pub`
- `/etc/kubernetes/pki/front-proxy-ca.crt`
- `/etc/kubernetes/pki/front-proxy-ca.key`
- `/etc/kubernetes/pki/etcd/ca.crt`
- `/etc/kubernetes/pki/etcd/ca.key`

Copy the admin kubeconfig to the other control plane nodes:

- `/etc/kubernetes/admin.conf`

In the following example, replace
`CONTROL_PLANE_IPS` with the IP addresses of the other control plane nodes.

```sh
USER=ubuntu # customizable
CONTROL_PLANE_IPS="10.0.0.7 10.0.0.8"
for host in ${CONTROL_PLANE_IPS}; do
    scp /etc/kubernetes/pki/ca.crt "${USER}"@$host:
    scp /etc/kubernetes/pki/ca.key "${USER}"@$host:
    scp /etc/kubernetes/pki/sa.key "${USER}"@$host:
    scp /etc/kubernetes/pki/sa.pub "${USER}"@$host:
    scp /etc/kubernetes/pki/front-proxy-ca.crt "${USER}"@$host:
    scp /etc/kubernetes/pki/front-proxy-ca.key "${USER}"@$host:
    scp /etc/kubernetes/pki/etcd/ca.crt "${USER}"@$host:etcd-ca.crt
    scp /etc/kubernetes/pki/etcd/ca.key "${USER}"@$host:etcd-ca.key
    scp /etc/kubernetes/admin.conf "${USER}"@$host:
done
```

{{< note >}}
**Note**: Remember that your config may differ from this example.
{{< /note >}}

### Add the second stacked control plane node

1.  Create a second, different `kubeadm-config.yaml` template file:

        apiVersion: kubeadm.k8s.io/v1alpha2
        kind: MasterConfiguration
        kubernetesVersion: v1.11.0
        apiServerCertSANs:
        - "LOAD_BALANCER_DNS"
        api:
            controlPlaneEndpoint: "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT"
        etcd:
          local:
            extraArgs:
              listen-client-urls: "https://127.0.0.1:2379,https://CP1_IP:2379"
              advertise-client-urls: "https://CP1_IP:2379"
              listen-peer-urls: "https://CP1_IP:2380"
              initial-advertise-peer-urls: "https://CP1_IP:2380"
              initial-cluster: "CP0_HOSTNAME=https://CP0_IP:2380,CP1_HOSTNAME=https://CP1_IP:2380"
              initial-cluster-state: existing
            serverCertSANs:
              - CP1_HOSTNAME
              - CP1_IP
            peerCertSANs:
              - CP1_HOSTNAME
              - CP1_IP
        networking:
            # This CIDR is a calico default. Substitute or remove for your CNI provider.
            podSubnet: "192.168.0.0/16"

1.  Replace the following variables in the template with the appropriate values for your cluster:

    - `LOAD_BALANCER_DNS`
    - `LOAD_BALANCER_PORT`
    - `CP0_HOSTNAME`
    - `CP0_IP`
    - `CP1_HOSTNAME`
    - `CP1_IP`

1.  Move the copied files to the correct locations:

      ```sh
      USER=ubuntu # customizable
      mkdir -p /etc/kubernetes/pki/etcd
      mv /home/${USER}/ca.crt /etc/kubernetes/pki/
      mv /home/${USER}/ca.key /etc/kubernetes/pki/
      mv /home/${USER}/sa.pub /etc/kubernetes/pki/
      mv /home/${USER}/sa.key /etc/kubernetes/pki/
      mv /home/${USER}/front-proxy-ca.crt /etc/kubernetes/pki/
      mv /home/${USER}/front-proxy-ca.key /etc/kubernetes/pki/
      mv /home/${USER}/etcd-ca.crt /etc/kubernetes/pki/etcd/ca.crt
      mv /home/${USER}/etcd-ca.key /etc/kubernetes/pki/etcd/ca.key
      mv /home/${USER}/admin.conf /etc/kubernetes/admin.conf
      ```

1.  Run the kubeadm phase commands to bootstrap the kubelet:

      ```sh
      kubeadm alpha phase certs all --config kubeadm-config.yaml
      kubeadm alpha phase kubelet config write-to-disk --config kubeadm-config.yaml
      kubeadm alpha phase kubelet write-env-file --config kubeadm-config.yaml
      kubeadm alpha phase kubeconfig kubelet --config kubeadm-config.yaml
      systemctl start kubelet
      ```

1.  Run the commands to add the node to the etcd cluster:

      ```sh
      export CP0_IP=10.0.0.7
      export CP0_HOSTNAME=cp0
      export CP1_IP=10.0.0.8
      export CP1_HOSTNAME=cp1

      export KUBECONFIG=/etc/kubernetes/admin.conf 
      kubectl exec -n kube-system etcd-${CP0_HOSTNAME} -- etcdctl --ca-file /etc/kubernetes/pki/etcd/ca.crt --cert-file /etc/kubernetes/pki/etcd/peer.crt --key-file /etc/kubernetes/pki/etcd/peer.key --endpoints=https://${CP0_IP}:2379 member add ${CP1_HOSTNAME} https://${CP1_IP}:2380
      kubeadm alpha phase etcd local --config kubeadm-config.yaml
      ```

      - This command causes the etcd cluster to become unavailable for a
      brief period, after the node is added to the running cluster, and before the
      new node is joined to the etcd cluster.

1.  Deploy the control plane components and mark the node as a master:

      ```sh
      kubeadm alpha phase kubeconfig all --config kubeadm-config.yaml
      kubeadm alpha phase controlplane all --config kubeadm-config.yaml
      kubeadm alpha phase mark-master --config kubeadm-config.yaml
      ```

### Add the third stacked control plane node

1.  Create a third, different `kubeadm-config.yaml` template file:

        apiVersion: kubeadm.k8s.io/v1alpha2
        kind: MasterConfiguration
        kubernetesVersion: v1.11.0
        apiServerCertSANs:
        - "LOAD_BALANCER_DNS"
        api:
            controlPlaneEndpoint: "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT"
        etcd:
          local:
            extraArgs:
              listen-client-urls: "https://127.0.0.1:2379,https://CP2_IP:2379"
              advertise-client-urls: "https://CP2_IP:2379"
              listen-peer-urls: "https://CP2_IP:2380"
              initial-advertise-peer-urls: "https://CP2_IP:2380"
              initial-cluster: "CP0_HOSTNAME=https://CP0_IP:2380,CP1_HOSTNAME=https://CP1_IP:2380,CP2_HOSTNAME=https://CP2_IP:2380"
              initial-cluster-state: existing
            serverCertSANs:
              - CP2_HOSTNAME
              - CP2_IP
            peerCertSANs:
              - CP2_HOSTNAME
              - CP2_IP
        networking:
            # This CIDR is a calico default. Substitute or remove for your CNI provider.
            podSubnet: "192.168.0.0/16"

1.  Replace the following variables in the template with the appropriate values for your cluster:

    - `LOAD_BALANCER_DNS`
    - `LOAD_BALANCER_PORT`
    - `CP0_HOSTNAME`
    - `CP0_IP`
    - `CP1_HOSTNAME`
    - `CP1_IP`
    - `CP2_HOSTNAME`
    - `CP2_IP`

1.  Move the copied files to the correct locations:

      ```sh
      USER=ubuntu # customizable
      mkdir -p /etc/kubernetes/pki/etcd
      mv /home/${USER}/ca.crt /etc/kubernetes/pki/
      mv /home/${USER}/ca.key /etc/kubernetes/pki/
      mv /home/${USER}/sa.pub /etc/kubernetes/pki/
      mv /home/${USER}/sa.key /etc/kubernetes/pki/
      mv /home/${USER}/front-proxy-ca.crt /etc/kubernetes/pki/
      mv /home/${USER}/front-proxy-ca.key /etc/kubernetes/pki/
      mv /home/${USER}/etcd-ca.crt /etc/kubernetes/pki/etcd/ca.crt
      mv /home/${USER}/etcd-ca.key /etc/kubernetes/pki/etcd/ca.key
      mv /home/${USER}/admin.conf /etc/kubernetes/admin.conf
      ```

1.  Run the kubeadm phase commands to bootstrap the kubelet:

      ```sh
      kubeadm alpha phase certs all --config kubeadm-config.yaml
      kubeadm alpha phase kubelet config write-to-disk --config kubeadm-config.yaml
      kubeadm alpha phase kubelet write-env-file --config kubeadm-config.yaml
      kubeadm alpha phase kubeconfig kubelet --config kubeadm-config.yaml
      systemctl start kubelet
      ```

1.  Run the commands to add the node to the etcd cluster:

      ```sh
      export CP0_IP=10.0.0.7
      export CP0_HOSTNAME=cp0
      export CP2_IP=10.0.0.9
      export CP2_HOSTNAME=cp2

      export KUBECONFIG=/etc/kubernetes/admin.conf 
      kubectl exec -n kube-system etcd-${CP0_HOSTNAME} -- etcdctl --ca-file /etc/kubernetes/pki/etcd/ca.crt --cert-file /etc/kubernetes/pki/etcd/peer.crt --key-file /etc/kubernetes/pki/etcd/peer.key --endpoints=https://${CP0_IP}:2379 member add ${CP2_HOSTNAME} https://${CP2_IP}:2380
      kubeadm alpha phase etcd local --config kubeadm-config.yaml
      ```

1.  Deploy the control plane components and mark the node as a master:

      ```sh
      kubeadm alpha phase kubeconfig all --config kubeadm-config.yaml
      kubeadm alpha phase controlplane all --config kubeadm-config.yaml
      kubeadm alpha phase mark-master --config kubeadm-config.yaml
      ```

## External etcd

### Set up the cluster

- Follow [these instructions](/docs/tasks/administer-cluster/setup-ha-etcd-with-kubeadm/)
   to set up the etcd cluster.

### Copy required files to other control plane nodes

The following certificates were created when you created the cluster. Copy them
to your other control plane nodes:

- `/etc/kubernetes/pki/etcd/ca.crt`
- `/etc/kubernetes/pki/apiserver-etcd-client.crt`
- `/etc/kubernetes/pki/apiserver-etcd-client.key`

In the following example, replace `USER` and `CONTROL_PLANE_HOSTS` values with values
for your environment.

```sh
USER=ubuntu
CONTROL_PLANE_HOSTS="10.0.0.7 10.0.0.8 10.0.0.9"
for host in $CONTROL_PLANE_HOSTS; do
    scp /etc/kubernetes/pki/etcd/ca.crt "${USER}"@$host:
    scp /etc/kubernetes/pki/apiserver-etcd-client.crt "${USER}"@$host:
    scp /etc/kubernetes/pki/apiserver-etcd-client.key "${USER}"@$host:
done
```

### Set up the first control plane node

1.  Create a `kubeadm-config.yaml` template file:

        apiVersion: kubeadm.k8s.io/v1alpha2
        kind: MasterConfiguration
        kubernetesVersion: v1.11.0
        apiServerCertSANs:
        - "LOAD_BALANCER_DNS"
        api:
            controlPlaneEndpoint: "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT"
        etcd:
            external:
                endpoints:
                - https://ETCD_0_IP:2379
                - https://ETCD_1_IP:2379
                - https://ETCD_2_IP:2379
                caFile: /etc/kubernetes/pki/etcd/ca.crt
                certFile: /etc/kubernetes/pki/apiserver-etcd-client.crt
                keyFile: /etc/kubernetes/pki/apiserver-etcd-client.key
        networking:
            # This CIDR is a calico default. Substitute or remove for your CNI provider.
            podSubnet: "192.168.0.0/16"

1.  Replace the following variables in the template with the appropriate values for your cluster:

    - `LOAD_BALANCER_DNS`
    - `LOAD_BALANCER_PORT`
    - `ETCD_0_IP`
    - `ETCD_1_IP`
    - `ETCD_2_IP`

1.  Run `kubeadm init --config kubeadm-config.yaml`

### Copy required files to the correct locations

The following certificates and other required files were created when you ran `kubeadm init`.
Copy these files to your other control plane nodes:

- `/etc/kubernetes/pki/ca.crt`
- `/etc/kubernetes/pki/ca.key`
- `/etc/kubernetes/pki/sa.key`
- `/etc/kubernetes/pki/sa.pub`
- `/etc/kubernetes/pki/front-proxy-ca.crt`
- `/etc/kubernetes/pki/front-proxy-ca.key`

In the following example, replace the list of
`CONTROL_PLANE_IPS` values with the IP addresses of the other control plane nodes.

```sh
USER=ubuntu # customizable
CONTROL_PLANE_IPS="10.0.0.7 10.0.0.8"
for host in ${CONTROL_PLANE_IPS}; do
    scp /etc/kubernetes/pki/ca.crt "${USER}"@$host:
    scp /etc/kubernetes/pki/ca.key "${USER}"@$host:
    scp /etc/kubernetes/pki/sa.key "${USER}"@$host:
    scp /etc/kubernetes/pki/sa.pub "${USER}"@$host:
    scp /etc/kubernetes/pki/front-proxy-ca.crt "${USER}"@$host:
    scp /etc/kubernetes/pki/front-proxy-ca.key "${USER}"@$host:
done
```

{{< note >}}
**Note**: Remember that your config may differ from this example.
{{< /note >}}

### Set up the other control plane nodes

1.  Verify the location of the copied files.
    Your `/etc/kubernetes` directory should look like this:

    - `/etc/kubernetes/pki/apiserver-etcd-client.crt`
    - `/etc/kubernetes/pki/apiserver-etcd-client.key`
    - `/etc/kubernetes/pki/ca.crt`
    - `/etc/kubernetes/pki/ca.key`
    - `/etc/kubernetes/pki/front-proxy-ca.crt`
    - `/etc/kubernetes/pki/front-proxy-ca.key`
    - `/etc/kubernetes/pki/sa.key`
    - `/etc/kubernetes/pki/sa.pub`
    - `/etc/kubernetes/pki/etcd/ca.crt`

1.  Run `kubeadm init --config kubeadm-config.yaml` on each control plane node, where
    `kubeadm-config.yaml` is the file you already created.

## Common tasks after bootstrapping control plane

### Install a pod network

[Follow these instructions](/docs/setup/independent/create-cluster-kubeadm/#pod-network) to install
the pod network. Make sure this corresponds to whichever pod CIDR you provided
in the master configuration file.

### Install workers

Each worker node can now be joined to the cluster with the command returned from any of the
`kubeadm init` commands.

{{% /capture %}}
