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00 — Getting Started with Kali Linux

What you'll learn: what Kali is, how to install it safely as a virtual machine, the very first things to do after booting, and how to keep it healthy. No prior Linux knowledge needed. Prerequisites: none — this is the first chapter. ⬅️ Course index

🐧 On a Linux PC? This chapter uses VirtualBox (easiest on Windows/macOS). If your own machine runs Linux, the native options — a KVM/QEMU VM or a Docker container, plus driving it all with Claude Code — are in Running Kali on a Linux host.

What is Kali Linux?

Linux is an operating system, like Windows or macOS, but free and open-source. Kali Linux is a version of Linux made by Offensive Security specifically for security testing — it comes with 600+ hacking and analysis tools already installed. Think of it as a fully-equipped workshop: instead of hunting down each tool, they're all in the drawer, ready.

You don't install Kali on your main computer. You run it in a virtual machine (VM) — a whole computer simulated inside a window on your real computer. That keeps Kali isolated and disposable: if you break it, you delete it and start over.

flowchart LR
    HOST["Your real PC<br/>(Windows/macOS)"] --> VM["VirtualBox / VMware"]
    VM --> KALI["Kali Linux VM<br/>the attacker"]
    VM --> LAB["Lab target VMs<br/>Metasploitable, Windows"]
    KALI -->|"host-only network<br/>192.168.56.0/24"| LAB

Step 1 — Install a hypervisor

A hypervisor is the software that runs VMs. Pick one (both are free): - VirtualBox — https://www.virtualbox.org/wiki/Downloads (easiest for beginners) - VMware Workstation Player — https://www.vmware.com/products/workstation-player.html

Install it like any normal program.

Step 2 — Get the Kali VM image

The easiest path: download Kali's pre-built VM (no manual install needed). - Go to https://www.kali.org/get-kali/#kali-virtual-machines - Download the VirtualBox (or VMware) image matching your hypervisor. - In VirtualBox: File → Import Appliance → select the downloaded file → Import.

Prefer building from scratch? Download the Installer ISO from the same page and create a new VM (2+ CPUs, 4+ GB RAM, 40+ GB disk), then install step-by-step. The pre-built image skips all that.

Step 3 — First boot & login

Start the VM. The default credentials for the pre-built image are: - Username: kali Password: kali

You'll land on a desktop. The most important icon is the Terminal (top bar, or Ctrl+Alt+T) — a window where you type commands. Almost everything in this course happens there.

Step 4 — The first three things to do

1. Change the default password (anyone knows kali/kali): 

passwd
Type your current password, then a new one twice (the screen won't show characters — that's normal).

2. Update everything. Kali changes fast; update before you start: 

sudo apt update && sudo apt full-upgrade -y
- sudo = "do this as the administrator (root)." It'll ask for your password. - apt = the tool that installs/updates software on Kali. - This can take a while the first time. Reboot afterward if it says to: sudo reboot.

3. Take a snapshot. In VirtualBox: Machine → Take Snapshot. A snapshot is a saved state you can instantly roll back to. Take one now ("clean install") and again before anything risky — it's your undo button.

Understanding sudo and root

Linux has a superuser called root who can do anything. For safety you normally work as the regular kali user and borrow root powers with sudo only when needed (installing software, raw network scans). If a command fails with "Permission denied," it often just needs sudo in front.

The Kali desktop, briefly

  • Terminal — where you type commands (your main tool).
  • Files — a graphical file browser.
  • Firefox — for research and for proxying web traffic through Burp later.
  • Applications menu — tools grouped by category (Information Gathering, Web Application Analysis, etc.). You'll mostly launch tools by typing their name in the terminal, which is faster.

Common beginner mistakes

  • Running Kali as your daily OS or on bare metal. Don't — use a VM; keep your real machine clean.
  • Skipping the update. Half of "this tool doesn't work" is a stale install. sudo apt update first.
  • Bridging the VM to your home network. Keep the lab on a host-only network so nothing escapes (see 03 — Networking basics and ../labs/topology.md).
  • Forgetting snapshots. Take one before experiments so a broken Kali is a 10-second rollback, not a reinstall.

✅ Practice task

  1. Import/boot Kali, log in, change the password.
  2. Run the full update, reboot.
  3. Open a terminal and run whoami (should print kali) and sudo whoami (should print root).
  4. Take a snapshot named "clean-updated".

Next

➡️ 01 — Linux essentials: moving around the filesystem, permissions, and installing tools.

Sources

  • Kali — Get Kali (VMs & ISOs): https://www.kali.org/get-kali/
  • Kali Docs — Installation: https://www.kali.org/docs/installation/
  • VirtualBox Manual: https://www.virtualbox.org/manual/