Ever had that heart-stopping moment when your website goes down? 😱 Or that frantic call from users who can’t access your application? 📱❌ High availability doesn’t have to be complicated or expensive. Enter Keepalived: your friendly neighbourhood service guardian! 🦸‍♂️

What is Keepalived? 🤔

Keepalived is like that reliable friend who always has your back. 🫂 It’s an open-source tool designed to provide high availability for Linux systems by automatically failing over to backup servers when your primary server gets into trouble. 🚨

At its core, Keepalived implements the Virtual Router Redundancy Protocol (VRRP), which allows multiple servers to share a virtual IP address. When one server fails, another takes over seamlessly—like a superhero swooping in to save the day! 🦸‍♀️💨

Why You’ll Love Keepalived ❤️

• Simple yet powerful: Does one thing and does it well 💪
• Lightweight: Minimal resource usage 🪶
• Battle-tested: Used in production environments worldwide 🌍
• Free and open-source: No licensing headaches! 🆓

Installing Keepalived 🛠️

Let’s get Keepalived up and running on your Linux system:

Ubuntu/Debian 🐧

sudo apt update
sudo apt install keepalived

CentOS/RHEL 🎩

sudo yum install keepalived

Verification ✅

Check if Keepalived is installed correctly:

keepalived --version

You should see version information displayed. Success! 🎉

Setting Up Your First High-Availability Pair 👯‍♂️

Let’s say you have two web servers that you want to configure for high availability. Here’s how to do it:

Create the Configuration File 📝

Primary Server Configuration /etc/keepalived/keepalived.conf 🥇

vrrp_instance WEB_HA {
    state MASTER
    interface eth0        # Your network interface
    virtual_router_id 51
    priority 101          # Higher number = higher priority
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass yourpassword  # Same on both servers
    }
    virtual_ipaddress {
        192.168.1.100     # Your virtual IP address
    }
}

Secondary Server Configuration /etc/keepalived/keepalived.conf 🥈

vrrp_instance WEB_HA {
    state BACKUP
    interface eth0        # Your network interface
    virtual_router_id 51
    priority 100          # Lower priority than the MASTER
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass yourpassword  # Same password as primary
    }
    virtual_ipaddress {
        192.168.1.100     # Same virtual IP as primary
    }
}

The main differences are:

• state is set to BACKUP instead of MASTER 🔄
• priority is lower (100 instead of 101) ⬇️

Start the Service 🚀

On both primary and backup servers:

sudo systemctl enable keepalived
sudo systemctl start keepalived

Test Your Setup 🧪

On your primary server, check if the virtual IP is assigned:

ip addr show eth0 #modify accordingly

You should see your virtual IP (192.168.1.100) listed.

Now for the fun part: simulate a failure by stopping Keepalived on your primary server: 😈

sudo systemctl stop keepalived

Check your secondary server—it should now have the virtual IP! Your services remain accessible without any downtime. 🪄

Beyond Basic Failover: Getting Creative with Keepalived 🎨

Keepalived isn’t just about IP failover. You can use it to:

Monitor Specific Services 🔍

Add health checks to ensure your web server is actually running:

vrrp_script check_web {
    script "curl -f http://localhost/ >/dev/null"
    interval 2
    weight 2
}

vrrp_instance WEB_HA {
    # ... other settings ...
    
    track_script {
        check_web
    }
}

Load Balancing ⚖️

Combine Keepalived with LVS (Linux Virtual Server) for load balancing:

virtual_server 192.168.1.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind NAT
    protocol TCP
    
    real_server 192.168.1.101 80 {
        weight 1
        TCP_CHECK {
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
    
    real_server 192.168.1.102 80 {
        weight 1
        TCP_CHECK {
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

Troubleshooting Tips 🔧

If things aren’t working as expected:

• Check logs: sudo journalctl -u keepalived 🔎
• Verify network: Ensure your servers can communicate 🌐
• Firewall rules: Make sure VRRP traffic (protocol 112) is allowed 🧱
• Interface names: Double-check your network interface names 🏷️

The Bottom Line 📊

Keepalived gives you enterprise-level high availability with minimal setup. It’s like insurance for your services—you hope you never need it, but you’ll be incredibly grateful when you do! 🛡️

Whether you’re running a small blog or a mission-critical application, Keepalived helps ensure your services stay accessible when hardware or software decides to take an unexpected vacation. 🏝️

Give it a try—your future self (and your users) will thank you when that inevitable server hiccup happens! 🙏