HACluster with Keepalived Ubuntu 22

To set up your servers and configure the hosts file, you need to follow these steps:

1. Create a new user on all servers and call it “webadmin” by running the following command:

   $ adduser webadmin 

2. Add the user “sysadmin” to the sudo group using the command:

   $ usermod -aG sudo webadmin 

3. Switch to the “webadmin” user:

   $ su - webadmin 

4. Use the sudo command to list the contents of the /root directory to test that the user is now part of the sudo group:

   $ sudo ls -la /root 

5. You can go one step further and add the following to sudoers file at the bottom to stop it asking you for a password every time you use the sudo command:
   
   $ sudo visudo
%webadmin ALL=(ALL) NOPASSWD:ALL
   
6. Make a backup copy of the /etc/hosts file by running this command:

   $ sudo cp -v /etc/hosts{,.bkup} 

7. Add the following entries to the hosts file: 

   # Load balancers
10.1.0.2 lb_1
10.1.0.3 lb_2
# Web servers
10.1.0.4 webserver_1
10.1.0.5 webserver_2

On all of the web servers, run the following commands:

$ sudo -i

$ apt update -y && sudo apt upgrade -y && sudo apt install -y apache2

--On Webserver_1
$ echo "This is webserver_1" > /var/www/html/index.html

--On Webserver_2
$ echo "This is webserver_2" > /var/www/html/index.html

$ systemctl enable apache2.service && systemctl start apache2 && sudo systemctl status apache2.service

On all of the load balancers, perform the following steps:

$ sudo -i
$ apt update -y && sudo apt upgrade -y && sudo apt install -y haproxy

$ cp -v /etc/haproxy/haproxy.conf{,.bkup}
or
$ cp -v /etc/haproxy/haproxy.cfg{,.bkup}

$ if [ -f /etc/haproxy/haproxy.conf ]; then nano /etc/haproxy/haproxy.conf; else nano /etc/haproxy/haproxy.cfg; fi

Replace the haproxy configuration with the following for lb_1:

global
  log /dev/log local0
  log /dev/log local1 notice
  chroot /var/lib/haproxy
  stats socket /run/haproxy/admin.sock mode 660 level admin
  stats timeout 30s
  user haproxy
  group haproxy
  daemon

defaults
  log global
  mode http
  option httplog
  option dontlognull
  timeout connect 5000
  timeout client 50000
  timeout server 50000

frontend my_frontend
  bind *:80
  default_backend my_backend

backend my_backend
  balance roundrobin
  server webserver_1 10.1.0.4:80 check
  server webserver_2 10.1.0.5:80 check

Replace the haproxy configuration with the following for lb_2:

global
  log /dev/log local0
  log /dev/log local1 notice
  chroot /var/lib/haproxy
  stats socket /run/haproxy/admin.sock mode 660 level admin
  stats timeout 30s
  user haproxy
  group haproxy
  daemon

defaults
  log global
  mode http
  option httplog
  option dontlognull
  timeout connect 5000
  timeout client 50000
  timeout server 50000

frontend my_frontend
  bind *:80
  default_backend my_backend

backend my_backend
  balance roundrobin
  server webserver_1 10.1.0.4:80 check
  server webserver_2 10.1.0.5:80 check

Test the haproxy configuration on both load balancers:

$ haproxy -f /etc/haproxy/haproxy.cfg -c

$ sudo systemctl enable haproxy && sudo systemctl restart haproxy && sudo systemctl status haproxy

Install keepalived on all load balancers:

$ apt install keepalived -y

Replace the keepalived configuration with the following for lb_1:

$ nano /etc/keepalived/keepalived.conf

global_defs {
    enable_script_security
}

vrrp_script chk_haproxy {
    script "killall -0 haproxy"   # Check if HAProxy process is running
    interval 2                   # Check every 2 seconds
    weight 2                     # Weight to influence master election
    user webadmin                # User you want the script to run as
}

vrrp_instance VI_1 {
    state MASTER
    interface enp0s8            # Network interface to bind to
    virtual_router_id 51
    priority 101                 # Higher priority on the primary server
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass **SVs2@k_-g6TD**     # Set a strong authentication password
    }
    virtual_ipaddress {
        10.1.0.6            # Your VIP address, this is the floating IP
    }
    track_script {
        chk_haproxy
    }
}

Replace the keepalived configuration with the following for lb_2:

global_defs {
    enable_script_security
}

vrrp_script chk_haproxy {
    script "killall -0 haproxy"   # Check if HAProxy process is running
    interval 2                   # Check every 2 seconds
    weight 2                     # Weight to influence master election
    user webadmin
}

vrrp_instance VI_1 {
    state BACKUP
    interface enp0s8             # Network interface to bind to
    virtual_router_id 51
    priority 100                 # Lower priority on the backup server
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass **SVs2@k_-g6TD**     # Same password as on the primary server
    }
    virtual_ipaddress {
        10.1.0.6            # Your VIP address, this is the floating IP
    }
    track_script {
        chk_haproxy
    }
}

Test the keepalived configuration and start the service on both load balancers:

$ keepalived -t
$ systemctl start keepalived && systemctl enable keepalived && systemctl status keepalived |grep Active

Check the IP addresses on both load balancers:

$ ip --brief add

Take down the interface on lb_1:

$ ip link set enp0s8 down

Test that both websites still load. If everything is working fine, the configuration is complete.

http://10.1.0.4

and

http://10.1.0.5

If you need to adjust your configurations then I would recommend following the documents here: https://www.haproxy.com/documentation/haproxy-configuration-tutorials/core-concepts/