When trying to update the packages on the Raspberry Pi, I got the following error:

E: Repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' changed its 'Suite' value from 'stable' to 'oldstable'
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.

This is because the current stable for Debian is now Bullseye, and Buster is considered ‘oldstable’
To fix the error and continue receiving Buster updates (whilst available) run:

apt-get update --allow-releaseinfo-change

You may need to run it as sudo

Eventually it will be better to upgrade your Raspbian version to the latest.

Would love your thoughts, please comment.x