This will be a quick article showing the process to flash the legacy Raspberry Pi OS 'Buster' Debian 10 (or any previous OS iteration) to a Micro-SD card. With any exciting new Operating System (OS) release, there are always small teething troubles, niggling issues, and compatibility problems that need to get ironed out (which no doubt the Raspberry Foundation and community are working furiously to do so with the Newest 'Bullseye' OS release). There are also certain packages (like recently the OMXPlayer or RaspiCamera) that can be dropped for the newer, often more open source, versions.
So, it is always nice to be able to roll back and tread familiar ground (and have your old scripts still function without altering them), thus this guide will demonstrate step by step how to flash and run 'Buster' OS (or any previous OS iteration) to your Raspberry Pi single-board computer (see image below).
If you happen to be holding a Raspberry Pi single-board computer and not quite sure what it is? Then check out this guide Raspberry Pi Generations to identify it. As always if you have got any questions, queries, or things you'd like to see added please let us know your thoughts!
Start off, if you haven't already, by finding and downloading the Official Imager Software by following this link. Install it to your desktop computer as you would any other program. [As of the end of January 2022 it is also available in the | Raspberry Pi OS (other) | menu of the Raspberry Pi Imager tool for flashing a microSD card.]
The next step is to get the original 'Buster' Image file onto your computer. Navigate to the official download repository for Buster OS. All earlier versions of Raspberry Pi OS can be found and downloaded here and the directly previous Raspberry Pi 'Buster' OS official download link is here. See below for what that looks like, download the image file by clicking on the highlighted file.
This will start the download of a zip file. This should take less than 8 minutes to download. See the downloaded file completed below.
Find this downloaded file in your file explorer. See this in the image below.
Right-click this file and choose to extract it. This process of unzipping the file will take less than 2 minutes. See this happening in the image below.
Having done this now check the location and enter the unzipped file folder. This folder will contain a Disc Image File (.img) of the 'Buster' Operating System. It should look like the image below.
We now have the image file of the previous 'Buster' OS on our computer. Now, let's open up the Official Raspberry Pi Imager, see it in the image below. Worth noting here - if you hit | CTRL+SHIFT+X | on your keyboard while in the Raspberry Pi Imager Program it will open the Advanced Hidden Menu. This Hidden Menu allows you to preconfigure your Raspberry Pi with SSH, WIFI credentials, and Localisation settings.
With the Official Raspberry Pi Imager open, click on the | CHOOSE OS | button and scroll, using your mouse wheel, all the way to the bottom of the menu to where you can see the | Use custom | option, see this in the image below. You will want to click this option.
Having done this it will open up a file explorer. Navigate to that extracted Disc Image File and click on it. See this in the image below. Then open the file image and this will arm the Raspberry Pi Imager with the Raspberry Pi 'Buster' OS. Find it, select it, and open it.
Insert the Micro-SD card that you want to be flashed into your computer. Use a USB to Micro-SD adapter if needed. Then click on the | CHOOSE STORAGE | button and select your inserted Micro-SD. Keep in mind any data that was on your Micro-SD card will be wiped/permanently deleted when it is flashed. The Official Raspberry Pi Imager will now look like the image below.
With everything sorted (the right OS loaded and the correct Storage selected) you can now click the | WRITE | button to start the flashing process. See this flashing process in the image below.
Once the flash is complete it will automatically virtually eject the Micro-SD card from the computer. So then you can simply physically take out your Micro-SD and insert it into a Raspberry Pi single-board computer. Then set your Raspberry Pi up normally as a desktop computer. Once it boots you will be greeted by the old familiar background, see image below, and you will have successfully flashed 'Buster' OS to your Raspberry Pi. You are free now to roam your well-acquainted digital ground.