Install HAProxy on RHEL 9

Step 1 – Install

dnf install -y haproxy
systemctl enable --now haproxy

Step 2 – Basic /etc/haproxy/haproxy.cfg

global
    log /dev/log local0
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin
    user haproxy
    group haprox...

Install Let's Encrypt SSL with Certbot (Apache) on RHEL 9

Step 1 – Install

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y certbot python3-certbot-apache

Step 2 – Obtain and install

certbot --apache -d example.com -d www.example.com

Step 3 – Ver

Install Let's Encrypt SSL with Certbot (Nginx) on RHEL 9

Step 1 – Install Certbot + Nginx plugin

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y certbot python3-certbot-nginx

Step 2 – Obtain certificate

certbot --nginx -d example.com -d www.exampl...

Install MariaDB on RHEL 9

Step 1 – Install and secure

dnf install -y mariadb-server
systemctl enable --now mariadb
mysql_secure_installation

Step 2 – Create database and user

CREATE DATABASE appdb CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
CREATE USER 'appuser'@'localhost' IDENTIFIED...

Install Memcached on RHEL 9

Step 1 – Install

dnf install -y memcached
systemctl enable --now memcached

Step 2 – Configure (/etc/sysconfig/memcached)

-l 127.0.0.1   # listen on localhost only
-m 256         # memory (MB)
-c 1024        # max connections
-t 4           # threads

Step 3 – V

Install ModSecurity WAF on Apache – RHEL 9

Step 1 – Install

dnf install -y mod_security
systemctl restart httpd

Step 2 – Enable detection mode

cp /etc/modsecurity/modsecurity.conf-recommended /etc/modsecurity/modsecurity.conf 2>/dev/null || \
   cp /usr/share/doc/libapache2-mod-security2/exa...

Install MySQL on RHEL 9

Step 1 – Install and secure

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y mysql-server
systemctl enable --now mysqld
mysql_secure_installation

Step 2 – Connect

mysql -u root -p

Step 3 – Create database and user

CREATE...

Install Nginx on RHEL 9

Step 1 – Update and enable EPEL

dnf update -y
subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms

Step 2 – Install Nginx

dnf install -y nginx

Step 3 – Enable and start

systemctl enable --now nginx

Step 4 – Firewall

firewall-cmd --perm...

Install Node.js on RHEL 9

Step 1 – Install

curl -fsSL https://rpm.nodesource.com/setup_20.x | bash -
dnf install -y nodejs

Step 2 – Verify

node --version && npm --version

Step 3 – Simple HTTP server

// app.js
const http = require('http');
http.createServer((req, res) => {
  res.writeHead...

Install Percona XtraDB Cluster (PXC) on RHEL 9

PXC provides synchronous multi-master MySQL replication using the Galera library.

Step 1 – Install

dnf install -y https://repo.percona.com/yum/percona-release-latest.noarch.rpm
percona-release enable-only pxc-80 release
dnf install -y percona-xtra...

Install PHP-FPM on RHEL 9

Step 1 – Install

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y php php-fpm php-cli php-opcache php-mysqlnd php-mbstring php-xml php-gd
systemctl enable --now php-fpm

Step 2 – Verify

php --version
php-fpm -v 2>/dev/null...

Install PostgreSQL on RHEL 9

Step 1 – Install

dnf install -y postgresql-server postgresql-contrib
postgresql-setup --initdb
systemctl enable --now postgresql

Step 2 – Connect as superuser

sudo -u postgres psql

Step 3 – Create database and user

CREATE USER appuser WITH PASSWORD 'StrongPas...

Install Prometheus on RHEL 9

Step 1 – Install

VERSION=2.51.2
wget https://github.com/prometheus/prometheus/releases/download/v${VERSION}/prometheus-${VERSION}.linux-amd64.tar.gz
tar xvf prometheus-${VERSION}.linux-amd64.tar.gz
cp prometheus-${VERSION}.linux-amd64/prometheus /usr/local/bin/
cp pr...

Install Redis on RHEL 9

Step 1 – Install

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y redis
systemctl enable --now redis

Step 2 – Verify

redis-cli ping   # PONG

Step 3 – Bind and password (/etc/redis/redis.conf)

bind 127.0.0.1 ::1
require...

Install Varnish Cache on RHEL 9

Step 1 – Install

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y varnish
systemctl enable --now varnish

Step 2 – Basic /etc/varnish/default.vcl

vcl 4.1;

backend default {
    .host = "127.0.0.1";
    .port = "8080...

Install WordPress on RHEL 9 (Nginx + PHP-FPM + MySQL)

Prerequisites

• Nginx · PHP-FPM · MySQL

Step 1 – Database

CREATE DATABASE wordpress CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
CREATE USER 'wpuser'@'localhost' IDENTIFIED BY 'WPStrongPass!';
GRANT ALL PRIVILEGES ON wordpress....

Integrate PHP-FPM with Nginx on RHEL 9

Prerequisites

PHP-FPM installed and running. See PHP-FPM install guide.

Socket path: /run/php-fpm/www.sock

Step 1 – Nginx server block

server {
    listen 80;
    server_name example.com;
    root /var/www/example.com/html;
    index index.php inde...

MariaDB Backup and Restore on RHEL 9

mariadb-dump (logical)

mariadb-dump -u root -p appdb > /backups/appdb_$(date +%F).sql
mariadb-dump -u root -p --all-databases --single-transaction > /backups/all_$(date +%F).sql

Restore

mariadb -u root -p appdb < /backups/appdb_2026-05-07.sql

Mariabacku

MariaDB Galera Cluster on RHEL 9

Nodes: 192.168.1.10 · 192.168.1.11 · 192.168.1.12

Step 1 – Install Galera on all nodes

dnf install -y mariadb-server-galera galera

Step 2 – Configure Node 1 (/etc/mysql/conf.d/galera.cnf)

[mysqld]
binlog_format            = ROW
default-storage-engine...

Memcached Distributed Setup on RHEL 9

Memcached itself has no cluster mode — distribution is handled by the client using consistent hashing.

Run multiple instances

memcached -d -l 192.168.1.10 -p 11211 -m 512 -t 4 -u memcache
memcached -d -l 192.168.1.11 -p 11211 -m 512 -t 4 -u memcache

syst

Monitor Percona XtraDB Cluster on RHEL 9

Key wsrep variables

SHOW STATUS LIKE 'wsrep_%';

MySQL Backup and Restore on RHEL 9

mysqldump

# Single database
mysqldump -u root -p appdb > /backups/appdb_$(date +%F).sql

# All databases
mysqldump -u root -p --all-databases > /backups/all_$(date +%F).sql

# Compressed
mysqldump -u root -p appdb | gzip > /backups/appdb_$(date +%F).sql.gz

Re

MySQL Primary-Replica Replication on RHEL 9

Primary: 192.168.1.10   Replica: 192.168.1.11

Primary – my.cnf

[mysqld]
server-id   = 1
log_bin     = /var/log/mysql/mysql-bin
binlog_format = ROW
binlog_expire_logs_seconds = 604800

CREATE USER 'replicator'@'192.168.1.11' IDENTIFIED WITH mysql...

Nginx Load Balancing on RHEL 9

Round-robin (default)

upstream myapp {
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080;
}
server {
    listen 80;
    server_name lb.example.com;
    location / { proxy_pass http://myapp; }
}

Least connections

upstream m...