Linux CLI

The shell remembers the commands you’ve typed — this is called command history. It’s one of the most productivity-boosting features of the command line, letting you recall, search, and rerun past commands instantly. How History Works Every command you enter is saved to a history list: Default behavior: Viewing History Command Description history Show all…

Every file and directory in Linux has permissions that control who can do what. Understanding permissions is essential for security and collaboration. Reading ls -l Output Let’s break down each column: File Type — The First Character Character Type Example – Regular file -rw-r–r– d Directory drwxr-xr-x l Symbolic link lrwxrwxrwx c Character device crw-rw-rw-…

These three commands handle user identity, file permissions, and default permission rules. Together, they form the foundation of Linux access control. Overview Command Purpose Best For id Show user identity Finding your UID, GID, and groups chmod Change permissions Setting who can read/write/execute umask Set default permissions Controlling defaults for new files The id Command…

Two commands for running things as another user — usually as root. They look similar but serve different purposes and have different security models. Overview Command Full Name Purpose su Substitute User Switch to another user (usually root) sudo SuperUser DO Run a single command with elevated privileges Key difference: The su Command Switches to…

These three commands manage ownership and passwords — who owns files, what group they belong to, and how user passwords are set up. Overview Command Purpose Best For chgrp Change group ownership Assigning files to teams/groups chown Change owner (and group) Transferring file ownership passwd Manage user passwords Setting, locking, expiring passwords The chgrp Command…

Processes are the running applications that consume system resources like CPU and memory. Every process has a unique PID (Process ID), and can be viewed with ps or top, and terminated with kill or pkill. What Are Processes? A process is an instance of a running program. Every command you run creates a process. Key…

Linux lets you run commands in the background while you continue working, manage those jobs, and safely shut down or reboot the system. Background vs Foreground Mode Description Terminal Blocked? Foreground Command runs normally, you wait for it ✅ Yes Background Command runs behind the scenes ❌ No Visual: Running Commands in the Background (&)…

Environment variables are key-value pairs that the shell and its child processes use to store information — your username, home directory, default editor, and much more. The printenv and export commands let you view and set these variables. What Are Environment Variables? Environment variables are dynamic values that affect how processes run. Variable Description HOME…

Nano is a popular command-line text editor on Unix-based systems. It’s open source, simple, and powerful — a favorite for beginners and system administrators alike. Introduction and Installation Nano comes pre-installed on many Linux distributions. If not, install it with: Debian / Ubuntu: RHEL / Fedora: Arch / Manjaro: openSUSE: Opening Files with Nano Command…

a – prompt customization intro You customize the CLI prompt by editing the PS1 variable. Permanent changes — edit the config file for your shell: Shell Config File Bash ~/.bashrc Zsh ~/.zshrc Fish ~/.config/fish/config.fish Example — set a permanent prompt: Apply the changes: Temporary testing — just set PS1 directly in the terminal: b –…