4. Getting Started with Kali Linux
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Kali Linux offers an easy start with a live disk image that allows you to boot directly without installation. It can be used for testing, forensics, or installation on physical or virtual hardware. However, due to its popularity, users are targeted by malicious actors. It's crucial to download Kali from trusted sources and verify its integrity to avoid fake versions, ensuring security, especially for professionals handling sensitive data.
To download Kali Linux, use only the official website's Downloads section at . While many third-party sites offer Kali images, they may be unreliable or contain malware. The website uses HTTPS and a valid TLS certificate, making it difficult for attackers to impersonate it. Downloads are hosted on the cdimage.kali.org domain, which redirects to a nearby mirror for faster speeds. A list of available mirrors is also provided at .
Kali Linux offers both 64-bit and 32-bit disk images. Most modern computers use 64-bit CPUs, but if unsure, you can check your system type (Windows), run the uname -m command (macOS), or inspect the /proc/cpuinfo file (Linux). Once you know your CPU type, choose between Installer, NetInstaller, or Live images. Live images allow running Kali without installation, while the others are for direct installs. You can download the image via HTTP or BitTorrent. Always verify the downloaded image’s integrity using the provided checksum.
To ensure that your downloaded Kali Linux image is legitimate and hasn't been tampered with, you should verify its integrity and authenticity using checksums and PGP signatures.
Why Verification is Important
Downloading an image from an external mirror poses security risks, as the mirror could be compromised. To mitigate this, the Kali project provides checksums for each image, but you must ensure the checksum you retrieve is genuinely from the Kali developers. Without verification, you may unknowingly use a compromised file.
1. Verifying Integrity via Checksums
Kali provides SHA256 checksums to ensure that the file you downloaded matches the official version. Here's how to check:
Generate the checksum for your downloaded image using the following command:
This will produce a hash value. Compare this with the checksum provided on the official Kali Linux download page.
If the checksums match, the file is correct. If they differ, the download might have been corrupted or tampered with, and you should try downloading it again from a different official mirror.
2. Verifying Authenticity with PGP
If you don't trust HTTPS, you can verify the integrity using PGP (Pretty Good Privacy). Here's how to verify the authenticity of the checksum file:
Import Kali's public GPG key:
Or, alternatively, fetch the key from a keyserver:
Verify the signature of the checksum file: Download the checksum and its signature:
Then verify the signature:
If the message shows "Good signature", you can trust the checksum file.
Verify the downloaded ISO file: To check if the ISO matches the official checksum:
If it returns OK, the ISO file is authentic.
Conclusion
Verifying the integrity and authenticity of your Kali Linux image ensures that you're using the correct, untampered file. If the checksums or signatures don't match, avoid using the file and download it again from a trusted mirror.
Unless you want to run Kali Linux in a virtual machine, the ISO image is of limited use in and of itself. You must burn it on a DVD-ROM or copy it onto a USB key to be able to boot your machine into Kali Linux. We have chosen the Kali live image as we wish to boot from a USB allowing us to either use a live environment or install Kali Linux's default configuration.
To install Kali Linux on a real computer, you need a prepared USB or a DVD-ROM with the Kali Linux ISO. Access the BIOS/UEFI settings by pressing a specific key (usually Delete, Escape, or F2-F12) right after powering on the computer. In the BIOS/UEFI, select the boot device (USB or DVD) and disable Secure Boot, as Kali Linux doesn't support it. Once configured, insert the bootable device and power on the system to boot into Kali Linux.
Using Kali Linux in a virtual machine (VM) offers many benefits, such as the ability to run multiple operating systems and experiment with tools safely. It's ideal for penetration testers and security professionals who need Kali's tools but still want access to their primary OS. VMs also allow easy archiving or secure deletion of Kali environments. Popular virtualization tools include VirtualBox and VMware Workstation. Ensure your CPU supports virtualization (Intel VT-x/VT-d) and that it's enabled in BIOS/UEFI. Additionally, use a 64-bit host OS for full functionality. Avoid running multiple virtualization tools simultaneously, and disable Hyper-V on Windows if needed.
What good examples can you think of for booting Kali live? What about bad examples?
Kali Live is great when you want to: keep a portable copy of Kali in your pocket; test out Kali Linux without making any changes on your computer; need to engage forensics mode. It's a bad idea to use Kali live as any kind of permanent installation, especially if you're hoping to save changes (no persistence!) or if you have limited memory on the boot machine.
Does it strike you weird that you can simply dd an ISO to a USB key, and have it boot?
The Kali (and Debian) ISO is an isohybrid. When the ISO is built, a syslinux utility runs the isohybrid command on the ISO, which adds a partition table to the ISO, while still keeping it a valid ISO file.
Hacker's Mantra: Kali Linux doesn’t make you a hacker, just as a scalpel doesn’t make you a surgeon. -- Anonymous