How to Install MariaDB Galera Cluster: Step-by-Step Guide

The MariaDB Galera Cluster offers a reliable solution for achieving database high availability and synchronous replication. It is commonly used in production environments where fault tolerance and data consistency matter. This tutorial walks you through setting up a basic MariaDB Galera Cluster on Linux servers.

Prerequisites

Three or more Linux servers (Ubuntu, CentOS, or similar) with static IPs.
Root or sudo access on all servers.
Basic knowledge of MariaDB/MySQL and Linux commands.
Open ports: 3306 (MariaDB), 4567 (Galera Cluster replication), 4568 (IST), 4444 (SST).
Firewall configured to allow above ports on all nodes.

Step 1: Setting Hostnames and Host File

Ensure all nodes can resolve each other’s hostnames. On each node, edit /etc/hosts to include:

192.168.1.101 node1
192.168.1.102 node2
192.168.1.103 node3

Replace IPs and hostnames with your server details.

Step 2: Install MariaDB with Galera Plugin

MariaDB versions 10.1 and above include Galera. Follow specific instructions depending on your Linux distribution.

For example, on Ubuntu:

sudo apt update
sudo apt install mariadb-server galera-4

On CentOS:

sudo yum install mariadb mariadb-server galera

Step 3: Configure MariaDB for Galera

Edit /etc/mysql/my.cnf or /etc/my.cnf.d/galera.cnf, add or modify the following:

[mysqld]
# Galera settings
wsrep_on=ON
wsrep_provider=/usr/lib/galera/libgalera_smm.so
wsrep_cluster_name="mariadb_galera_cluster"
wsrep_cluster_address="gcomm://192.168.1.101,192.168.1.102,192.168.1.103"
wsrep_node_address="192.168.1.101"  # Change on each node
wsrep_node_name="node1"           # Change on each node
wsrep_sst_method=rsync
binlog_format=ROW
default_storage_engine=InnoDB
innodb_autoinc_lock_mode=2

Important: Change wsrep_node_address and wsrep_node_name for each node respectively.

Step 4: Initialize the Cluster

On the first node, start the cluster with bootstrap:

sudo systemctl stop mariadb
sudo galera_new_cluster

Then start MariaDB normally on the other nodes:

sudo systemctl start mariadb

Step 5: Verify Cluster Status

Log into MariaDB on each node:

mysql -u root -p

Run:

SHOW STATUS LIKE 'wsrep_cluster_size';

The output should reflect the total number of nodes in the cluster.

Step 6: Test Data Replication

Create a test database and insert data on one node.
Verify the data appears instantly on all other nodes.

Troubleshooting Tips

Cluster does not start: Ensure the wsrep_cluster_address is correctly set and firewall ports are open.
Nodes do not join cluster: Check network connectivity and matching Galera versions.
SST fails: Confirm rsync is installed as it’s used for State Snapshot Transfer.
Check logs: MariaDB logs are usually in /var/log/mysql/ or /var/log/mariadb/.