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OSI and TCP/IP Models — What Every Developer & Sysadmin Should Know
Practical comparison of the 7-layer OSI model and 4-layer TCP/IP model, packet encapsulation, and bottom-up network debugging techniques.
IP Subnetting and CIDR in 10 Minutes — A Practical Guide
Complete beginner guide to IPv4 addresses, CIDR prefix notation, calculating usable hosts, subnet masks, RFC 1918 private ranges, and CLI tools.
DNS A and AAAA Records — Pointing Domains at IP Addresses
Complete beginner guide to IPv4 A records and IPv6 AAAA records, dual-stack configurations, TTL tuning strategies, and CLI verification with dig.
Linux Filesystem Permissions — rwx, chmod, chown, and sudo Hygiene
Complete beginner guide to Linux file permissions, user/group ownership, chmod and chown commands and flags, umask, and safe sudo rules.
Fail2ban — Protect SSH and Web Services from Brute Force
Install, configure, and operate fail2ban to automatically block malicious IP addresses attempting brute-force logins.
tmux — Terminal Multiplexer for Persistent SSH Sessions
Complete beginner guide to tmux, managing persistent sessions across SSH disconnects, splitting terminal panes, keyboard shortcuts, and configuration.
Install and Secure phpMyAdmin on Ubuntu & Debian
Step-by-step beginner guide to installing phpMyAdmin, configuring blowfish cookie encryption, custom URL aliases, and securing access behind IP and VPN allow-lists.
JavaScript fetch() Basics — Asynchronous HTTP, JSON, and Error Handling
Complete beginner guide to the modern JavaScript fetch API, handling HTTP errors with res.ok, POSTing JSON payloads, and request timeouts with AbortController.