Every so often, the Raspberry Pi orgnization issues a new release of the operating system for the Raspberry Pi. Most recently, and coincident with the debut of the Rapspberry Pi 4B+, is the Debian Buster operating system. Before Buster were Jessie and Stretch.
When a major update to the operating system is issued, I have to re-format the SD memory card.
Then install the memory image on the card. I have to add a couple of files in order to communicate with the RPi without using an external monitor and keyboard. I can go 'headless' and use my local wifi router and my laptop to run SSH sessions.
Once communications is established, I set some system parameters. Next, I begin downloading and installing programs and other software to run on the RPi.
This process, with testing, can take half a day or more. For this reason, I keep a backup of the SD card once I'm done with updates and modifications. This way, if a card goes bad or some damage occurs, I'll have a spare ready for installation. Just plug and run.
