Kernel Drivers

How to Set Up ModSecurity WAF with Apache on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Set Up ModSecurity WAF with Apache on RHEL 9

ModSecurity is the leading open-source Web Application Firewall (WAF), capable of inspecting all HTTP requests and responses against a ruleset and blocking malicious traffic including SQL injection, cross-site scripting (XSS), remote file inclusion, and OWASP Top 10 attack patterns. Combined with the OWASP Core Rule Set (CRS), ModSecurity transforms Apache into a security gateway that […]

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How to Configure Nginx Load Balancing (Round-Robin, Least Conn) on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure Nginx Load Balancing (Round-Robin, Least Conn) on RHEL 9

Load balancing distributes incoming requests across multiple backend servers, preventing any single server from becoming a bottleneck and providing horizontal scalability and fault tolerance. Nginx supports four load balancing methods natively: round-robin (the default), least connections, IP hash (session persistence), and weight-based. The upstream block defines the pool of backend servers and their weights, and […]

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How to Configure Apache mod_proxy as a Reverse Proxy on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure Apache mod_proxy as a Reverse Proxy on RHEL 9

Apache’s mod_proxy module turns Apache into a powerful reverse proxy and gateway, forwarding requests to backend application servers, other web servers, or balancer clusters. Unlike Nginx’s reverse proxy (which is native), Apache’s proxy functionality is modular: mod_proxy handles the core proxying, mod_proxy_http handles HTTP/1.1, mod_proxy_balancer provides load balancing, and mod_proxy_wstunnel handles WebSocket tunnelling. On RHEL […]

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How to Install Apache HTTP Server on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Install Apache HTTP Server on RHEL 9

Apache HTTP Server (httpd) is the most historically significant web server in the history of the internet, powering billions of websites since 1995. On RHEL 9, Apache is available as httpd from the AppStream repository and integrates with SELinux, firewalld, and systemd. Apache’s module architecture makes it highly extensible: mod_rewrite for URL manipulation, mod_ssl for […]

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How to Manage System Packages with dnf on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Manage System Packages with dnf on RHEL 9

dnf (Dandified YUM) is the default package manager for RHEL 9 and the successor to yum. It handles installing, updating, removing, and querying RPM packages from local and remote repositories, resolving dependencies automatically using the libsolv library, and supporting transactions that can be rolled back if something goes wrong. For Red Hat Enterprise Linux, packages […]

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How to Perform a System Security Audit with auditd on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Perform a System Security Audit with auditd on RHEL 9

Security auditing is the practice of recording and reviewing system calls, file accesses, user actions, and configuration changes to detect policy violations, investigate incidents, and demonstrate compliance with standards like PCI DSS, HIPAA, and SOC 2. On RHEL 9, the Linux Audit Framework — provided by the auditd daemon — captures events at the kernel […]

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How to Use journalctl for Systemd Log Analysis on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Use journalctl for Systemd Log Analysis on RHEL 9

The Linux kernel’s systemd journal is a structured binary log that stores the output of every service, kernel message, boot sequence, and user session. Unlike traditional text-based syslog, the journal stores metadata alongside each log entry — the unit name, PID, UID, executable path, systemd unit state, and priority level — enabling far more precise […]

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How to Monitor Disk Usage with df, du, lsblk and ncdu on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Monitor Disk Usage with df, du, lsblk and ncdu on RHEL 9

Running out of disk space is one of the most disruptive failures a server can experience. When a filesystem fills up, applications crash, log files stop writing (losing audit trails), databases corrupt transactions, and web servers return 500 errors. Proactive disk monitoring is essential — and RHEL 9 provides a full set of tools for […]

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Initial Server Setup with RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

Initial Server Setup with RHEL 9

Red Hat Enterprise Linux 9 (RHEL 9, codenamed “Plow”) is the most significant release of RHEL in years, built on Linux kernel 5.14, OpenSSL 3.0, and shipped with a hardened-by-default security posture including SELinux enforcing mode, nftables as the default firewall backend, and full support for the latest POWER, ARM, and x86_64 architectures. Whether you […]

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How to Configure the Firewall on RHEL 9 with firewalld — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure the Firewall on RHEL 9 with firewalld

Red Hat Enterprise Linux 9 uses firewalld as its default firewall management daemon, backed by nftables as the kernel netfilter framework (replacing iptables which was the default in RHEL 7 and earlier). firewalld provides a zone-based model where each network interface is assigned to a trust zone — public, internal, dmz, trusted, and more — […]

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