Linux Reference
Linux Reference is a free, complete guide to 304+ Linux commands and concepts. Every entry includes its full syntax, the most useful options, a practical example you can paste straight into a terminal, and a difficulty rating so you know whether it is aimed at beginners or experienced administrators. Browse by category: File Operations, Text Processing, System Info, Process Management, Network, Permissions, Archives & Compression, Disk & Storage, Package Management, Shell & Scripting, Search & Find, SSH & Remote, Git, Performance, Date & Time. Popular starting points include ls, cd, pwd, mkdir, rmdir, rm, cp, mv, touch, cat, less, head, tail, ln, file, stat, grep, sed, awk, sort. If you are new to the command line, start with the file operation and text processing categories; if you administer servers, the networking, permissions, and package management sections cover the daily toolkit. Use the search page to jump straight to any command, the cheat sheet for a quick lookup, or the blog for deep dives on terminal productivity and system administration.