Linux Virtual Server is a highly salable and highly available server built on a cluster of real servers with the load balance running on the Linux Operating System.
First of all we will install the Linux Virtual Server package on Our CentOS 8 / RHEL 8 machine. After Installing LVS on our Operating System we will configure it as a load balancer to the back end servers. This setup assumes you have installed a CentOS / RHEL 8 server or workstation edition.
Step 1: Installing Linux Virtual Server on CentOS 8 / RHEL 8
Run the following command on your server to Install Linux Virtual Server and Choose yes to proceed further.
[sabi@localhost ~]$ sudo yum install ipvsadm
[sudo] password for sabi:
Last metadata expiration check: 3:38:25 ago on Sun 22 Dec 2019 12:37:06 AM EST.
Package Arch Version Repository Size
ipvsadm x86_64 1.29-8.el8 AppStream 57 k
Install 1 Package
Total download size: 57 k
Installed size: 83 k
Is this ok [y/N]: y
Step 2: Enabling IP forwarding and enable service
When you have finished installing package, enable the service and IP forwarding in your machine.
echo 'net.ipv4.ip_forward = 1' | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
Confirm it is turned to 1
[sabi@localhost ~]$ echo 'net.ipv4.ip forward = 1' | sudo tee -a /etc/sysctl.conf
[sudo] password for sabi:
net.ipv4.ip forward = 1
Start and enable ipvsadm services by running
sudo touch /etc/sysconfig/ipvsadm
sudo systemctl enable –now ipvsadm
Check out the service status, it will be look like as:
[sabi@localhost ~]$ systemctl status ipvsadm
● ipvsadm.service - Initialise the Linux Virtual Server
Loaded: loaded (/usr/lib/systemd/system/ipvsadm.service; enabled; vendor preset: di>
Active: active (exited) since Sun 2019-12-22 04:25:30 EST; 20s ago
Process: 5880 ExecStart=/bin/bash -c exec /sbin/ipvsadm-restore < /etc/sysconfig/ipv>
Main PID: 5880 (code=exited, status=0/SUCCESS)
Dec 22 04:25:29 localhost.localdomain systemd: Starting Initialise the Linux Virtua>
Dec 22 04:25:30 localhost.localdomain systemd: Started Initialise the Linux Virtual>
lines 1-8/8 (END)
Step 3: Configure LVS as Load Balancer
After setting up all, move forward to configure LVS as a load balancer to actual back-end applications.
Clean the IP tables rules by running
sudo ipvsadm -C
Step 4: Adding a Virtual Service
Add a virtual service by using the syntax
ipvsadm -A -t (ServiceIP:Port) -s (Distribution method)
Following Distribution methods supported:
- rr (Round Robin) = Equal load distribution among back-end servers
- wrr (Weighted Round Robin) = The Round Robin based on real Servers weight
- lc (Least Connection) = Servers having few active processes are selected for new load assignment on priority basis.
- wlc ( Weighted Least Connection) = Assigns tasks to servers with fewer jobs and relative to the real server’s weight (Ci/Wi) . By default, this method is used.
We will do configuration based on below diagram.
In this case, I’m setting LVS server to listen on 192.168.233.129 with port 80.
sudo ipvsadm -A -t 192.168.233.129:80 -s wlc
Now, add the back-end servers by typing
sudo ipvsadm -a -t (ServiceIP:Port) -r (BackendServerIP:Port) -m
The configuration will look like
sudo ipvsadm -a -t 192.168.233.129:80 -r 192.168.233.209:80 -m
sudo ipvsadm -a -t 192.168.233.129:80 -r 192.168.233.4:80 -m
Type the following command to list current rules:
[sabi@localhost ~]$ sudo ipvsadm -l
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP cent01:http wlc
-> cent03:http Masq 1 0 0
-> cent02:http Masq 1 0 0
sudo firewall-cmd --add-service=http --permanent
sudo firewall-cmd --reload
Now, when you load the LVS server IP / domain name from the browser, you will see the page on one of the back-end server.
Hi this is the LVS server page on back-end server 1
Upon reloading, the back-end server 2 page should show
Hi this is the LVS server page on back-end server 2
This is how you can set up your LVS server on CentOS 8 / RHEL 8.