Prometheus Node Exporter is the standard agent for exposing hardware and operating system metrics from Linux hosts to a Prometheus server. It collects data on CPU usage, memory, disk I/O, network throughput, filesystem utilisation, and dozens of other system-level indicators, making them available via a simple HTTP endpoint on port 9100. Installing Node Exporter on […]
OpenVPN is a mature, battle-tested VPN solution that supports TLS-based encryption and X.509 certificate authentication, making it well-suited for enterprise environments where certificate lifecycle management and strong mutual authentication are required. Unlike WireGuard, OpenVPN can traverse firewalls over TCP port 443, which is useful when UDP is blocked. On RHEL 9, OpenVPN 2.x is available […]
Ruby on Rails (Rails) is a full-stack web application framework built on Ruby that made convention-over-configuration and the MVC pattern mainstream in web development. Rails provides ActiveRecord (ORM), ActionController (routing and controllers), ActionView (templating with ERB/Haml), ActionMailer, ActiveJob (background jobs), ActionCable (WebSockets), and a comprehensive set of security defaults out of the box. A Rails […]
Spring Boot is the most widely used Java web framework, providing an opinionated, auto-configured platform for building standalone, production-ready applications. Spring Boot embeds an HTTP server (Tomcat, Jetty, or Undertow) directly in the application JAR, eliminating the need for a separate application server deployment. A Spring Boot application is packaged as an executable “fat JAR” […]
Keepalived implements the Virtual Router Redundancy Protocol (VRRP) on Linux, allowing two or more servers to share a single virtual IP address (VIP). If the master server fails, the backup server automatically claims the VIP within seconds, providing high availability with no changes required on clients or DNS. On RHEL 9, Keepalived integrates cleanly with […]
LUKS (Linux Unified Key Setup) is the standard disk encryption framework on Linux, providing transparent block-level encryption that protects data at rest even if physical media is stolen. On RHEL 9, LUKS is backed by the cryptsetup tool and integrates tightly with the kernel’s device mapper subsystem. This tutorial walks through encrypting a new disk […]
Port knocking is a security technique that hides your SSH port from network scanners by keeping it firewalled until a specific sequence of connection attempts is made. On RHEL 9, combining knockd with nftables lets you expose SSH only to clients who know the secret knock sequence, dramatically reducing brute-force exposure. This tutorial walks through […]
The perf tool is the Linux kernel’s built-in performance analysis framework, capable of sampling CPU events, tracing system calls, counting hardware performance counters, and generating flame graphs — all without any changes to the application under test. On RHEL 9, perf integrates tightly with the kernel’s BPF and tracepoint subsystems, making it one of the […]
Docker Compose is a tool for defining and running multi-container Docker applications from a single YAML configuration file (docker-compose.yml or compose.yaml). Instead of manually running multiple docker run commands and configuring networks and volumes by hand, Docker Compose allows you to declare all services (web application, database, cache, message queue) in one file and start […]
SELinux (Security-Enhanced Linux) enforces Mandatory Access Control (MAC) on RHEL 9, confining processes to only the resources they are explicitly permitted to access regardless of traditional Unix file permissions. While RHEL ships with comprehensive base policies, custom applications often generate AVC (Access Vector Cache) denials because their access patterns are not covered by existing policy […]
