A free, self-paced textbook in 8 chapters. Read a chapter, then drill it with the 542 companion flashcards using spaced repetition.
The Secure Shell (SSH) is the workhorse for remote Linux administration, and almost every aspect of it can be customized. The per-user ~/.ssh/config file lets administrators define...
DNS is the addressing layer of the internet, and Linux administrators must understand its record types. An A record maps a domain to an IPv4 address, AAAA to IPv6, and CNAME create...
Modern Linux distributions manage services through systemd, and a small set of systemctl verbs covers most needs. systemctl start, stop, and restart control running state, while re...
User account information is split across three traditional files: /etc/passwd (usernames, UIDs, GIDs, home, shell), /etc/shadow (password hashes and aging, readable only by root),...
Linux exposes block devices through a virtual filesystem populated by udev, the kernel's device manager that creates entries under /dev dynamically as hardware appears and disappea...
Modern Linux networking is configured with the ip family of commands. ip addr shows interfaces with their addresses and state; ip addr add IP/PREFIX dev IFACE assigns one, ip addr...
The two leading open-source web servers on Linux are nginx and Apache. nginx configuration lives in /etc/nginx/nginx.conf with site definitions under sites-available/ and sites-ena...
Process inspection starts with ps (for example, ps aux --sort=-%mem for top memory users and ps -ejH for hierarchy) and pstree -p for a tree view. pgrep returns PIDs matching a nam...