---
reviewers:
- mikedanese
- luxas
- errordeveloper
- jbeda
title: Creating HA clusters with kubeadm
content_template: templates/task
---

{{% capture overview %}}

This guide shows you how to install and set up a highly available Kubernetes cluster using kubeadm.

This document shows you how to perform setup tasks that kubeadm doesn't perform: provision hardware; configure multiple systems; and load balancing.

{{< note >}}
**Note:** This guide is only one potential solution, and there are many ways to configure a highly available cluster. If a better solution works for you, please use it. If you find a better solution that can be adopted by the community, feel free to contribute it back.
{{< /note >}}

{{% /capture %}}

{{% capture prerequisites %}}

- 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
- **Optional:** At least three machines that meet [kubeadm's minimum requirements](/docs/setup/independent/install-kubeadm/#before-you-begin)
   if you intend to host etcd on dedicated nodes (see information below)
- 1GB or more of RAM per machine (any less will leave little room for your apps)
- Full network connectivity between all machines in the cluster (public or
   private network is fine)

{{% /capture %}}

{{% capture steps %}}

## Installing prerequisites on masters

For each master that has been provisioned, follow the [installation guide](/docs/setup/independent/install-kubeadm/) on how to install kubeadm and its dependencies. At the end of this step, you should have all the dependencies installed on each master.

## Setting up an HA etcd cluster

For highly available setups, you will need to decide how to host your etcd cluster. A cluster is composed of at least 3 members. We recommend one of the following models:

- Hosting etcd cluster on separate compute nodes (Virtual Machines)
- Hosting etcd cluster on the master nodes.

While the first option provides more performance and better hardware isolation, it is also more expensive and requires an additional support burden.

For **Option 1**: create 3 virtual machines that follow [CoreOS's hardware recommendations](https://coreos.com/etcd/docs/latest/op-guide/hardware.html). For the sake of simplicity, we will refer to them as `etcd0`, `etcd1` and `etcd2`.

For **Option 2**: you can skip to the next step. Any reference to `etcd0`, `etcd1` and `etcd2` throughout this guide should be replaced with `master0`, `master1` and `master2` accordingly, since your master nodes host etcd.

### Create etcd CA certs

1. Install `cfssl` and `cfssljson` on all etcd nodes:

     ```bash
     curl -o /usr/local/bin/cfssl https://pkg.cfssl.org/R1.2/cfssl_linux-amd64
     curl -o /usr/local/bin/cfssljson https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64
     chmod +x /usr/local/bin/cfssl*
     ```

1. SSH into `etcd0` and run the following:

      ```bash
     mkdir -p /etc/kubernetes/pki/etcd
     cd /etc/kubernetes/pki/etcd

     cat >ca-config.json <<EOF
     {
        "signing": {
            "default": {
                "expiry": "43800h"
            },
            "profiles": {
                "server": {
                    "expiry": "43800h",
                    "usages": [
                        "signing",
                        "key encipherment",
                        "server auth",
                        "client auth"
                    ]
                },
                "client": {
                    "expiry": "43800h",
                    "usages": [
                        "signing",
                        "key encipherment",
                        "client auth"
                    ]
                },
                "peer": {
                    "expiry": "43800h",
                    "usages": [
                        "signing",
                        "key encipherment",
                        "server auth",
                        "client auth"
                    ]
                }
            }
        }
     }
     EOF
     ```
     ```bash
     cat >ca-csr.json <<EOF
     {
        "CN": "etcd",
        "key": {
            "algo": "rsa",
            "size": 2048
        }
     }
     EOF
     ```

    {{< note >}}**Optional:** You can modify `ca-csr.json` to add a section for `names`.
    See [the CFSSL wiki](https://github.com/cloudflare/cfssl/wiki/Creating-a-new-CSR) for an example.
    {{< /note >}}

1. Next, generate the CA certs:
     ```bash
     cfssl gencert -initca ca-csr.json | cfssljson -bare ca -
     ```

### Generate etcd client certs

Generate the client certificates. While on `etcd0`, run the following:

```bash
cat >client.json <<EOF
{
  "CN": "client",
  "key": {
      "algo": "ecdsa",
      "size": 256
  }
}
EOF
```
```bash
cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=client client.json | cfssljson -bare client
```

Both `client.pem` and `client-key.pem` are created.

### Create SSH access

In order to copy certs between machines, you must enable SSH access for `scp`.

1. First, open new tabs in your shell for `etcd1` and `etcd2`. Ensure you are SSHed into all three machines and then run the following (it will be a lot quicker if you use tmux syncing - to do this in iTerm enter `cmd+shift+i`):

     ```bash
     export PEER_NAME=$(hostname)
     export PRIVATE_IP=$(ip addr show eth1 | grep -Po 'inet \K[\d.]+')
     ```

    Make sure that `eth1` corresponds to the network interface for the IPv4 address of the private network. This might vary depending on your networking setup, so please check by running `echo $PRIVATE_IP` before continuing.

1. Next, generate some SSH keys for the boxes:
     ```bash
     ssh-keygen -t rsa -b 4096 -C "<email>"
     ```

    Make sure to replace `<email>` with your email, a placeholder, or an empty string. Keep hitting enter until files exist in `~/.ssh`.

1. Output the contents of the public key file for `etcd1` and `etcd2`:
     ```bash
     cat ~/.ssh/id_rsa.pub
     ```

1. Finally, copy the output for each and paste them into `etcd0`'s `~/.ssh/authorized_keys` file. This will permit `etcd1` and `etcd2` to SSH in to the machine.

### Generate etcd server and peer certs

1. In order to generate certs, each etcd machine needs the root CA generated by `etcd0`. On `etcd1` and `etcd2`, run the following:
     ```bash
     mkdir -p /etc/kubernetes/pki/etcd
     cd /etc/kubernetes/pki/etcd
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca.pem .
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca-key.pem .
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client.pem .
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client-key.pem .
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca-config.json .
     ```

     Where `<etcd0-ip-address>` corresponds to the public or private IPv4 of `etcd0`.

1. Once this is done, run the following on all etcd machines:
     ```bash
     cfssl print-defaults csr > config.json
     sed -i '0,/CN/{s/example\.net/'"$PEER_NAME"'/}' config.json
     sed -i 's/www\.example\.net/'"$PRIVATE_IP"'/' config.json
     sed -i 's/example\.net/'"$PEER_NAME"'/' config.json
     ```
     ```bash
     cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=server config.json | cfssljson -bare server
     cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=peer config.json | cfssljson -bare peer
     ```

     The above will replace the default configuration with your machine's hostname as the peer name, and its IP addresses. Make sure
     these are correct before generating the certs. If you found an error, reconfigure `config.json` and re-run the `cfssl` commands.

This results in the following files: `peer.pem`, `peer-key.pem`, `server.pem`, `server-key.pem`.

### {{< tabs name="etcd_mode" >}}
{{% tab name="Choose one..." %}}
Please select one of the tabs to see installation instructions for the respective way to set up a virtual IP.
{{% /tab %}}
{{% tab name="systemd" %}}
1. First, install etcd binaries:
     ```bash
     export ETCD_VERSION="v3.1.12" 
     curl -sSL https://github.com/coreos/etcd/releases/download/${ETCD_VERSION}/etcd-${ETCD_VERSION}-linux-amd64.tar.gz | tar -xzv --strip-components=1 -C /usr/local/bin/
     ```

    It is worth noting that etcd v3.1.12 is the preferred version for Kubernetes v1.10. For other versions of Kubernetes please consult [the changelog](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG.md).

    Also, please realize that most distributions of Linux already have a version of etcd installed, so you will be replacing the system default.

1. Next, generate the environment file that systemd will use:
     ```bash
     touch /etc/etcd.env
     echo "PEER_NAME=${PEER_NAME}" >> /etc/etcd.env
     echo "PRIVATE_IP=${PRIVATE_IP}" >> /etc/etcd.env
     ```

1. Now copy the systemd unit file:
     ```none
     cat >/etc/systemd/system/etcd.service <<EOF
     [Unit]
     Description=etcd
     Documentation=https://github.com/coreos/etcd
     Conflicts=etcd.service
     Conflicts=etcd2.service

     [Service]
     EnvironmentFile=/etc/etcd.env
     Type=notify
     Restart=always
     RestartSec=5s
     LimitNOFILE=40000
     TimeoutStartSec=0

     ExecStart=/usr/local/bin/etcd --name <name> --data-dir /var/lib/etcd --listen-client-urls https://<etcd-listen-ip>:2379 --advertise-client-urls https://<etcd-listen-ip>:2379 --listen-peer-urls https://<etcd-listen-ip>:2380 --initial-advertise-peer-urls https://<etcd-listen-ip>:2380 --cert-file=/etc/kubernetes/pki/etcd/server.pem --key-file=/etc/kubernetes/pki/etcd/server-key.pem --client-cert-auth --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.pem --peer-cert-file=/etc/kubernetes/pki/etcd/peer.pem --peer-key-file=/etc/kubernetes/pki/etcd/peer-key.pem --peer-client-cert-auth --peer-trusted-ca-file=/etc/kubernetes/pki/etcd/ca.pem --initial-cluster <etcd0>=https://<etcd0-ip-address>:2380,<etcd1>=https://<etcd1-ip-address>:2380,<etcd2>=https://<etcd2-ip-address>:2380 --initial-cluster-token my-etcd-token --initial-cluster-state new

     [Install]
     WantedBy=multi-user.target
     EOF
     ```

     Make sure you replace `<etcd0-ip-address>`, `<etcd1-ip-address>` and `<etcd2-ip-address>` with the appropriate IPv4 addresses. Replace `<name>` with the name of this etcd member. Replace `<etcd-listen-ip>` with the IPv4 address of this etcd node. Replace `<etcd0>`, `<etcd1>` and `<etcd2>` with real hostnames of each machine. These machines must be able to reach each other using DNS or by adding records to `/etc/hosts`.

1. Finally, launch etcd:
     ```bash
     systemctl daemon-reload
     systemctl start etcd
     ```

1. Check that it launched successfully:
     ```bash
     systemctl status etcd
     ```

{{% /tab %}}
{{% tab name="Static Pods" %}}
**Note**: This is only supported on nodes that have the all dependencies for the kubelet installed. If you are hosting etcd on the master nodes, this has already been set up. If you are hosting etcd on dedicated nodes, you should either use systemd or run the [installation guide](/docs/setup/independent/install-kubeadm/) on each dedicated etcd machine.

Run the following to generate the manifest file:

<!-- Using indentation instead of code fencing because of https://github.com/russross/blackfriday/issues/239 -->
      cat >/etc/kubernetes/manifests/etcd.yaml <<EOF
      apiVersion: v1
      kind: Pod
      metadata:
        labels:
          component: etcd
          tier: control-plane
        name: <name>
        namespace: kube-system
      spec:
        containers:
        - command:
          - etcd --name <name> 
          - --data-dir /var/lib/etcd 
          - --listen-client-urls https://<etcd-listen-ip>:2379 
          - --advertise-client-urls https://<etcd-listen-ip>:2379 
          - --listen-peer-urls https://<etcd-listen-ip>:2380 
          - --initial-advertise-peer-urls https://<etcd-listen-ip>:2380 
          - --cert-file=/certs/server.pem 
          - --key-file=/certs/server-key.pem 
          - --client-cert-auth 
          - --trusted-ca-file=/certs/ca.pem 
          - --peer-cert-file=/certs/peer.pem 
          - --peer-key-file=/certs/peer-key.pem 
          - --peer-client-cert-auth 
          - --peer-trusted-ca-file=/certs/ca.pem 
          - --initial-cluster etcd0=https://<etcd0-ip-address>:2380,etcd1=https://<etcd1-ip-address>:2380,etcd2=https://<etcd2-ip-address>:2380 
          - --initial-cluster-token my-etcd-token 
          - --initial-cluster-state new
          image: k8s.gcr.io/etcd-amd64:3.1.10
          livenessProbe:
            httpGet:
              path: /health
              port: 2379
              scheme: HTTP
            initialDelaySeconds: 15
            timeoutSeconds: 15
          name: etcd
          env:
          - name: PUBLIC_IP
            valueFrom:
              fieldRef:
              fieldPath: status.hostIP
          - name: PRIVATE_IP
            valueFrom:
              fieldRef:
                fieldPath: status.podIP
          - name: PEER_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          volumeMounts:
          - mountPath: /var/lib/etcd
            name: etcd
          - mountPath: /certs
            name: certs
      hostNetwork: true
      volumes:
      - hostPath:
          path: /var/lib/etcd
          type: DirectoryOrCreate
        name: etcd
      - hostPath:
          path: /etc/kubernetes/pki/etcd
        name: certs
      EOF

Make sure you replace:

* `<name>` with the name of the node you're running on (for example, `etcd0`, `etcd1` or `etcd2`)
* `<etcd-listen-ip>` with the public IPv4 address of the node you're running on
* `<etcd0-ip-address>`, `<etcd1-ip-address>` and `<etcd2-ip-address>` with the public IPv4s of the other machines that host etcd.

{{% /tab %}}
{{< /tabs >}}

## Set up master Load Balancer

## {{< tabs name="lb_mode" >}}
{{% tab name="Choose one..." %}}
Please select one of the tabs to see installation instructions for the respective way to set up a virtual IP.
{{% /tab %}}
{{% tab name="Cloud" %}}
Some examples of cloud provider solutions are:

* [AWS Elastic Load Balancer](https://aws.amazon.com/elasticloadbalancing/)
* [GCE Load Balancing](https://cloud.google.com/compute/docs/load-balancing/)
* [Azure](https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-overview)

You will need to ensure that the load balancer routes to **just `master0` on port 6443**. This is because kubeadm will perform health checks using the load balancer IP. Since `master0` is set up individually first, the other masters will not have running apiservers, which will result in kubeadm hanging indefinitely.

If possible, use a smart load balancing algorithm like "least connections", and use health checks so unhealthy nodes can be removed from circulation. Most providers will provide these features.
{{% /tab %}}
{{% tab name="On-Site" %}}
In an on-site environment there may not be a physical load balancer available. Instead, a virtual IP pointing to a healthy master node can be used. There are a number of solutions for this including keepalived, Pacemaker and probably many others, some with and some without load balancing.

As an example we outline a simple setup based on keepalived. Depending on environment and requirements people may prefer different solutions. The configuration shown here provides an _active/passive_ failover without load balancing. If required, load balancing can by added quite easily by setting up HAProxy, NGINX or similar on the master nodes (not covered in this guide).

1. Install keepalived, e.g. using your distribution's package manager. The configuration shown here works with version `1.3.5` but is expected to work with may other versions. Make sure to have it enabled (chkconfig, systemd, ...) so that it starts automatically when the respective node comes up.

2. Create the following configuration file `/etc/keepalived/keepalived.conf` on all master nodes:
     ```none
     ! Configuration File for keepalived
     global_defs {
      router_id LVS_DEVEL
     }

     vrrp_script check_apiserver {
      script "/etc/keepalived/check_apiserver.sh"
      interval 3
      weight -2
      fall 10
      rise 2
     }

     vrrp_instance VI_1 {
        state <STATE>
        interface <INTERFACE>
        virtual_router_id 51
        priority <PRIORITY>
        authentication {
            auth_type PASS
            auth_pass 4be37dc3b4c90194d1600c483e10ad1d
        }
        virtual_ipaddress {
            <VIRTUAL-IP>
        }
        track_script {
            check_apiserver
        }
     }
     ```

    In the section `vrrp_instance VI_1`, change the following lines depending on your setup:

    * `state` is either `MASTER` (on the first master nodes) or `BACKUP` (the other master nodes).
    * `interface` is the name of an existing public interface to bind the virtual IP to (usually the primary interface).
    * `priority` should be higher for the first master node, e.g. 101, and lower for the others, e.g. 100.
    * `auth_pass` use any random string here.
    * `virtual_ipaddresses` should contain the virtual IP for the master nodes.

3. Install the following health check script to `/etc/keepalived/check_apiserver.sh` on all master nodes:
     ```bash
     #!/bin/sh

     errorExit() {
        echo "*** $*" 1>&2
        exit 1
     }

     curl --silent --max-time 2 --insecure https://localhost:6443/ -o /dev/null || errorExit "Error GET https://localhost:6443/"
     if ip addr | grep -q <VIRTUAL-IP>; then
        curl --silent --max-time 2 --insecure https://<VIRTUAL-IP>:6443/ -o /dev/null || errorExit "Error GET https://<VIRTUAL-IP>:6443/"
     fi
     ```

    Replace the `<VIRTUAL-IP>` by your chosen virtual IP.

4. Restart keepalived. While no Kubernetes services are up yet it will log health check fails on all master nodes. This will stop as soon as the first master node has been bootstrapped.
{{% /tab %}}
{{< /tabs >}}


## Acquire etcd certs

Only follow this step if your etcd is hosted on dedicated nodes (**Option 1**). If you are hosting etcd on the masters (**Option 2**), you can skip this step since you've already generated the etcd certificates on the masters.

1. Generate SSH keys for each of the master nodes by following the steps in the [create ssh access](#create-ssh-access) section. After doing this, each master will have an SSH key in `~/.ssh/id_rsa.pub` and an entry in `etcd0`'s `~/.ssh/authorized_keys` file.

1. Run the following:
     ```bash
     mkdir -p /etc/kubernetes/pki/etcd
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/ca.pem /etc/kubernetes/pki/etcd
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client.pem /etc/kubernetes/pki/etcd
     scp root@<etcd0-ip-address>:/etc/kubernetes/pki/etcd/client-key.pem /etc/kubernetes/pki/etcd
     ```

## Run kubeadm init on master0 {#kubeadm-init-master0}

1.  In order for kubeadm to run, you first need to write a configuration file:

<!-- Using indentation instead of code fencing because of https://github.com/russross/blackfriday/issues/239 -->
      cat >config.yaml <<EOF
      apiVersion: kubeadm.k8s.io/v1alpha1
      kind: MasterConfiguration
      api:
        advertiseAddress: <virtual-ip>
        controlPlaneEndpoint: <virtual-ip>
      etcd:
        endpoints:
        - https://<etcd0-ip-address>:2379
        - https://<etcd1-ip-address>:2379
        - https://<etcd2-ip-address>:2379
        caFile: /etc/kubernetes/pki/etcd/ca.pem
        certFile: /etc/kubernetes/pki/etcd/client.pem
        keyFile: /etc/kubernetes/pki/etcd/client-key.pem
      networking:
        podSubnet: <podCIDR>
      apiServerCertSANs:
      - <virtual-ip>
      - <private-ip>
      apiServerExtraArgs:
        apiserver-count: "3"
      EOF

Ensure that the following placeholders are replaced:

- `<private-ip>` with the private IPv4 of the master server.
- `<etcd0-ip>`, `<etcd1-ip>` and `<etcd2-ip>` with the IP addresses of your three etcd nodes
- `<podCIDR>` with your Pod CIDR. Please read the [CNI network section](/docs/setup/independent/create-cluster-kubeadm/#pod-network) of the docs for more information. Some CNI providers do not require a value to be set.
- `<virtual-ip>` with the virtual IP. Please read [setting up a master load balancer](/docs/setup/independent/high-availability/#set-up-master-load-balancer) section of the docs for more information.

{{< note >}}**Note:** If you are using Kubernetes 1.9+, you can replace the `apiserver-count: 3` extra argument with `endpoint-reconciler-type: lease`. For more information, see [the documentation](/docs/admin/high-availability/#endpoint-reconciler).{{< /note >}}

1.  When this is done, run kubeadm:
      ```bash
      kubeadm init --config=config.yaml
      ```

## Run kubeadm init on master1 and master2

Before running kubeadm on the other masters, you need to first copy the K8s CA cert from `master0`. To do this, you have two options:

### Option 1: Copy with scp

1. Follow the steps in the [create ssh access](#create-ssh-access) section, but instead of adding to `etcd0`'s `authorized_keys` file, add them to `master0`.
1. Once you've done this, run:

     ```bash
     scp root@<master0-ip-address>:/etc/kubernetes/pki/* /etc/kubernetes/pki
     rm /etc/kubernetes/pki/apiserver*
     ```

### Option 2: Copy paste

Copy the contents of `/etc/kubernetes/pki/ca.crt`, `/etc/kubernetes/pki/ca.key`, `/etc/kubernetes/pki/sa.key` and `/etc/kubernetes/pki/sa.pub` and create these files manually on `master1` and `master2`.

When this is done, you can follow the [previous step](#kubeadm-init-master0) to install the control plane with kubeadm.

## Add master1 and master2 to load balancer

Once kubeadm has provisioned the other masters, you can add them to the load balancer pool.

## Install CNI network

Follow the instructions [here](/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

Next provision and set up the worker nodes. To do this, you will need to provision at least 3 Virtual Machines.

1. To configure the worker nodes, [follow the same steps](/docs/setup/independent/create-cluster-kubeadm/#joining-your-nodes) as non-HA workloads.

## Configure workers

1. Reconfigure kube-proxy to access kube-apiserver via the load balancer:
     ```bash
     kubectl get configmap -n kube-system kube-proxy -o yaml > kube-proxy-cm.yaml
     sed -i 's#server:.*#server: https://<masterLoadBalancerFQDN>:6443#g' kube-proxy-cm.yaml
     kubectl apply -f kube-proxy-cm.yaml --force
     # restart all kube-proxy pods to ensure that they load the new configmap
     kubectl delete pod -n kube-system -l k8s-app=kube-proxy
     ```

1. Reconfigure the kubelet to access kube-apiserver via the load balancer:
     ```bash
     sudo sed -i 's#server:.*#server: https://<masterLoadBalancerFQDN>:6443#g' /etc/kubernetes/kubelet.conf
     sudo systemctl restart kubelet
     ```
