linux
GNU/Linux
History
- Started in 1983 by Richard Stallman, the GNU Project aimed to build a free Unix-like OS
- By the early 1990s, GNU lacked a kernel until Linus Torvalds created the Linux kernel in 1991, released under the GNU GPL in 1992
- Together, they formed GNU/Linux, a free, open-source alternative to proprietary Unix
- GNU/Linux is packaged into user-friendly distributions like Ubuntu, Debian, and Fedora, each offering unique features and interfaces
Key features
- Free and open-source, unlike paid Unix systems
- GNU tools paired with the Linux kernel
- Kernel manages CPU, memory, and storage
- Distributions (e.g., Ubuntu for beginners, Debian for stability, Fedora for cutting-edge updates) make GNU/Linux accessible
Learn more
Linux Directory Structure
Shell, Console, and Terminal
Console
- Physical devices to interact with the computer such as screen, keyboard, and mouse
Terminal
- A program acts as a wrapper to enter commands
Shell
- A command line interpreter that receives and executes commands
Basic Commands
Fun fact
- A directory is a just a file containing the names of other files
- Sudo: Superuser do
| Category | Popular Commands |
|---|---|
| File & Directory Management | ls, cd, pwd, cp, mv, rm, mkdir, touch, ln -s |
| Viewing & Editing Files | cat, less, head, tail, nano, vim |
| Searching Files & Text | find, grep, locate, wc |
| User & Group Management | sudo, su, useradd, usermod, userdel, groupadd, passwd, id, who, whoami, last, w |
| Permissions & Security | chmod, chown, chgrp, visudo, getfacl, setfacl, openssl, fail2ban |
| Process & Performance | ps, top, htop, kill, killall, vmstat, iostat, free, lsof, ulimit -a |
| Disk & Filesystem | df -h, du -sh, lsblk, mount, umount, fdisk -l, mkfs |
| System & Hardware Info | uname, uptime, hostname, lscpu, lsblk, lspci, lsusb, lshw, dmidecode |
| Networking | ping, ip/ifconfig, ssh, scp, wget, curl, ss, netstat, traceroute, nmap, dig, host |
| System Services (systemd) | systemctl (start, stop, enable, status), journalctl, shutdown, reboot |
| Firewall Management | iptables, firewalld (firewall-cmd), ufw |
| Archiving & Backup | tar, gzip, gunzip, zip, unzip, rsync, dd, dump, restore |
| Package Management | apt/dnf/yum/pacman (install, remove, update, search) |
| Remote Administration | ssh, scp, tmux, screen, watch |
| System Logging | journalctl, dmesg, tail -f /var/log/syslog, logrotate |
| Job Scheduling | crontab -e, crontab -l, at |
| Shell & Environment | echo, export, alias, source, env, history, man, --help, clear |
| Development & Misc. Tools | git, make, gcc/g++, tee, sleep, which, type, xargs |
| Web & Database Services | apachectl, nginx -s, mysql, psql |
| Containerization | docker/podman (ps, images, run, stop), virsh, kvm |
Practice
telnet google 80
man telnet
telnet --help
which telnet
ls /usr/bin | grep telnet
docker ps -a | awk 'NR>2 {print $2}'
find . -type f -size +1G
find . -type d -size +1G
du -sh *
df -h
top
su kyphan -s /bin/bash
chmod o-rx tmp
chmod -R o-rx tmp
cd /etc
cat passwd
cat group
cat hosts
cat sudoers