A reverse proxy sits in front of one or more backend application servers, forwarding client requests to them and returning their responses to the client. From the client’s perspective, the reverse proxy is the web server. This architecture provides centralized SSL termination, load balancing, caching, rate limiting, and DDoS mitigation without exposing backend application ports […]
Apache virtual hosts are the mechanism by which a single Apache HTTP Server instance serves multiple websites, distinguishing between them using the ServerName directive and the incoming Host HTTP header. Name-based virtual hosting (the most common type) allows hundreds of domains to share a single IP address, with Apache routing each request to the correct […]
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 […]
Nginx (pronounced “engine-x”) is the most widely deployed web server in the world, powering everything from small personal websites to the largest content delivery networks. On RHEL 9, Nginx is available from the AppStream repository and integrates natively with SELinux, firewalld, and systemd. Its event-driven, non-blocking architecture means a single Nginx worker process can handle […]
Network configuration on RHEL 9 is managed by NetworkManager, and the primary tools for working with it are nmcli (NetworkManager Command-Line Interface) and the traditional ip command from the iproute2 package. Understanding both is essential: nmcli creates persistent network profiles that survive reboots and are managed by NetworkManager, while the ip command makes temporary changes […]
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 […]
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 […]
Every Linux administrator needs at least one terminal text editor in their toolkit. When a remote server is accessible only via SSH with no GUI, when a configuration file needs editing before a service can start, or when you are recovering a broken system from a rescue shell, your text editor is your primary interface. […]
rsync is the Swiss Army knife of file synchronisation for Linux administrators. Unlike scp, which blindly copies every file every time, rsync computes a rolling checksum to identify changed file blocks and transfers only what has changed — making subsequent syncs dramatically faster and less bandwidth-intensive. It preserves file attributes (permissions, ownership, timestamps, ACLs, extended […]
DNS resolution on a Linux server is a multi-layered system. When an application calls getaddrinfo(“example.com”), the request passes through the Name Service Switch (NSS) framework, which consults sources in the order defined in /etc/nsswitch.conf — typically /etc/hosts first, then a DNS resolver. The DNS resolver reads its configuration from /etc/resolv.conf, which lists the DNS servers […]
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