The Library

Everything you need to know about virtual machines, operating systems, Linux, servers, kernels, SSH, and essential terminal commands — explained with real-world analogies.

How computers talk to each other — from IP addresses and DHCP to NAT, SSH tunnels, SCP file transfers, and VM networking. The concepts every engineer needs to understand.

What Bash actually is, how files and directories work, the Linux filesystem structure, the root user, switching users with su, and mastering the ls command family.

Linux file permissions demystified — who can read, write, and execute files, how chmod numbers work, reading ls -l output, SSH permission requirements, and advanced SUID/SGID/Sticky bits.

Why typing 'ls' works but your own script doesn't. How Linux finds commands using $PATH, three ways to run your scripts, how to safely modify $PATH, and nano — the terminal text editor.

What systemd is, how to control services with systemctl, what daemons are, reading logs with journalctl, and the full Linux boot sequence from power-on to login prompt.

What lives in /bin, /sbin, and /etc. How inodes store file metadata. And LVM — the flexible storage system that lets you expand disk space on a live server in 10 seconds.

What ports are, the well-known port numbers every engineer should know, how ufw firewall works, hardening SSH against brute-force attacks, Fail2ban, and how DNS translates google.com to an IP in 20ms.

How Linux runs tasks automatically while you sleep. The cron schedule format explained, reading and writing crontab files, practical production examples, and how to log cron output.

Why 'it works on my machine' killed careers. How Docker containers solve environment differences. Container vs VM. Images, Dockerfiles, Docker Hub. And nginx — the web server powering a third of the internet.