Debian is a GNU / Linux based operating system. Debian OS, like most Linux distributions, is completely free and open source. This popular operating system is often installed on desktop computers and servers. The Debian OS has also spawned several well-known offshoots such as Ubuntu. Debian is developed and distributed by a non-profit organization, and the operating system itself can be downloaded absolutely free from the official website. Installing Debian is straightforward: you need an internet connection, disk imaging software, and a blank CD or USB stick.
Steps
Method 1 of 2: Installing from CD

Step 1. Make a copy of all important files from your computer
Installing Debian will wipe the hard drive and format it. Before proceeding with the installation of the operating system, save all important information to an external hard drive.

Step 2. Launch your browser and go to the Debian website
Debian can be downloaded from the official website www.debian.org, and all the necessary files can be found on the Where to get Debian page.

Step 3. Download the installation image
Download an installation image from the website that matches your processor architecture. If you do not know which processor is installed on your computer, please select the 32-bit PC netinst iso as it is compatible with most 32-bit Intel and AMD processors.

Step 4. Burn the installation image to CD or DVD
The downloaded image file (the file will have the ".iso" extension) to disk using a program for creating disk images. This can be done using a number of free programs, but only if a CD-R or DVD-R drive is already installed in the computer. If your computer can enable booting from a USB drive, you can also write the disk image to a flash drive.

Step 5. Start your computer from the newly burned disc
Leave the disc with the.iso file written on it in the drive and restart the computer. After the system boots from disk, the Debian Installation Wizard will appear on the screen.

Step 6. If desired, the user can try Debian Live by running it from disk
You have the option to start the operating system from a CD or DVD without overwriting the information on your hard drive (this option is called Debian Live). Select this option in the installation wizard if you want to try out Debian before installing it on your computer. Please note that the system will have rather low performance, and all actions will be performed with a delay.

Step 7. Install Debian following the instructions of the installation wizard
Follow the instructions on the screen to customize the operating system as you wish and proceed with the OS installation. The system will give you the option to partition your hard drive if in the future you want to install not only Debian, but also another operating system such as Microsoft Windows.
Method 2 of 2: Installing from a USB stick

Step 1. Make a copy of all important files on your computer
Installing Debian will completely clear the hard drive and format it, erasing all data stored in the previous OS. Therefore, you should save all important information to an external hard drive. Once Debian is installed, all of this information can be easily recovered.

Step 2. Take out the USB stick and make a copy of its contents
This stick will act as the Debian installer. All contents on the flash drive will be erased, so back up any important files.
The volume of the drive must be at least 2 GB

Step 3. Install the program for creating a bootable USB flash drive (Live USB)
There are many programs available to create bootable flash drives. UNetBootin is available for Windows, Mac OS X and Linux users. Further in the article we will use this particular program.
If you choose to use a different program, these instructions can also be applied to most programs that allow you to create bootable flash drives

Step 4. Download the disk image
Go to the Debian website and open the "Where to get Debian" tab. Here you can download both a small and a full installation image. Choose the one that suits you best.
- Download a small installation image if your computer is connected to the Internet.
- Download the complete image if your computer is not connected to the Internet. This image contains more packages, making it easier to install on devices without an Internet connection.
As downloading the file can take a long time, use the torrent download option. If BitTorrent is installed on your computer, the file download will be much faster

Step 5. Run the program to create a bootable USB drive
Open the Windows Start Menu and type UNetBootin into the search bar. Launch Spotlight on Mac OS X and enter the same keyword. Most likely, you will be prompted to run the program with administrator rights. Enter your password and press Enter.

Step 6. Open the image file
Click on the "Disk Image" radio button. Make sure ISO Standard is checked in the drop-down menu, then click on the button on the right to open File Explorer. In this window, find the ISO file and open it.

Step 7. Write the installer to a flash drive
Make sure the Type drop down menu at the bottom of the window is USB Device and that the correct drive is selected in the Media menu. This is very important because the wrong choice can format another flash drive or, even worse, format the hard drive. Click on the "OK" button to start creating a bootable USB drive.
This process may take some time. Save and close all open windows as the installation requires a restart to start

Step 8. Restart your computer and enter the boot menu
Save your current work and restart your computer. When the manufacturer's splash screen appears on the monitor, a key will be indicated in the bottom corner / bottom line of the screen, with which you can enter the boot menu. Press this key on your keyboard.
- If this option was not present, it is most likely hidden in the BIOS. Enter BIOS and go to the Boot Menu tab.
- If a key is not listed during computer boot that will enter the boot menu or BIOS, search for your computer model on the Internet and find out which key to press. Typically, these are the F2, F11, F12, or Del keys.
- In the boot menu, the flash drive will be labeled with the manufacturer's name (Lexar, SanDisk, etc.) or "Debian + OS name and version number". Select this option to download the installation file.

Step 9. Follow the instructions in the installation wizard
Connect your computer to your modem using an Ethernet cable so you don't lose your internet connection during installation. Enter the required information at each step. If you want to install Debian alongside another operating system, such as Windows, at the end of the installation you will be given the option to partition your hard drive.
Advice
- If for any reason you are unable to download and install the installation image, buy a Debian installation disc from the website.
- It can take a while to install the Debian OS, so find yourself something to do.