> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apinizer.com/llms.txt
> Use this file to discover all available pages before exploring further.

# High Availability Cluster

> You can perform Kubernetes high availability cluster installation. You can configure multi-master node configuration using HAProxy and Keepalived and provide continuous accessibility with virtual IP address.

## 1) HAProxy Installation

HAProxy is an open-source proxy and load balancing solution used to provide load balancing and high availability. Installation on Ubuntu operating systems is described below.

```bash theme={null}
sudo apt update
```

HAProxy installation is performed.

```bash theme={null}
sudo apt install haproxy
```

Configuration file is edited.

```bash theme={null}
sudo vi /etc/haproxy/haproxy.cfg
```

You can add the following commands to the bottom of the file. Edit the hostname and IP fields according to yourself.

```bash theme={null}
frontend kubernetes-frontend
  bind *:6443
  mode tcp
  option tcplog
  default_backend kubernetes-backend

backend kubernetes-backend
  option httpchk GET /healthz
  http-check expect status 200
  mode tcp
  option ssl-hello-chk
  balance roundrobin
  server <master1hostname> <MASTER_1_IP>:6443 check fall 3 rise 2
  server <master2hostname> <MASTER_2_IP>:6443 check fall 3 rise 2
  server <master3hostname> <MASTER_3_IP>:6443 check fall 3 rise 2
```

```bash theme={null}
systemctl enable haproxy && systemctl restart haproxy
systemctl status haproxy
```

## 2) Keepalived Installation

Keepalived provides a virtual IP address between multiple control nodes (master and backup masters) and is used to ensure continuous operation of other services.

```bash theme={null}
sudo apt install keepalived
```

```bash theme={null}
sudo vim /etc/keepalived/check_apiserver.sh
```

The following script performs availability check to the Kubernetes API server. Replace the \<VIRTUAL\_IP> part with the virtual ip you will add in the next step.

```bash theme={null}
#!/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

```

```bash theme={null}
chmod +x /etc/keepalived/check_apiserver.sh
```

```bash theme={null}
sudo vim /etc/keepalived/keepalived.conf
```

If the keepalived.conf file is not empty, you can clear its content and add the following command lines.

**Important:** Add the appropriate network unit opposite the interface. Replace the \<VIRTUAL\_IP> part with the IP address you want to add.

```bash theme={null}
vrrp_script check_apiserver {
  script "/etc/keepalived/check_apiserver.sh"
  interval 3
  timeout 10
  fall 5
  rise 2
  weight -2
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth1
    virtual_router_id 1
    priority 100
    advert_int 5
    authentication {
        auth_type PASS
        auth_pass mysecret
    }
    virtual_ipaddress {   
     <VIRTUAL_IP>    
 }
    track_script {
        check_apiserver
    }
}
```

```bash theme={null}
systemctl enable --now keepalived
```

## Starting Kubernetes Cluster

You can perform Kubernetes installation from the [Kubernetes Installation on Ubuntu Operating System](/en/setup/kubernetes/ubuntu-kubernetes) document.

<Warning>
  **Important:** When performing the init operation, you must enter your own virtual IP address to the endpoint as follows.
</Warning>

```bash theme={null}
kubeadm init --control-plane-endpoint="<VIRTUAL_IP>:6443" --upload-certs --pod-network-cidr=10.244.0.0/16
```