If you’ve got an older Buster install (Raspberry Pi OS or piaware sdcard image), and it has not been updated for a while, when updating using apt-get you may run into this error:
E: Repository 'http://flightaware.com/mirror/raspbian/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 unfortunately does affect PiAware 5.0 sdcard images. We’re looking at workarounds to allow auto-updating.
To fix this manually, run:
sudo apt update
(note: not apt-get, just apt). It will prompt you to accept the changes. Say yes:
E: Repository 'http://flightaware.com/mirror/raspbian/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.
Do you want to accept these changes and continue updating from this repository? [y/N] Y
(The tl;dr on the details of this is that this is present in older versions of apt and triggered by the upstream Debian release of the next version of Debian, bullseye – even if you are not updating to bullseye. An update was released for buster to work around this, but if you hadn’t updated between the buster update and the release of bullseye, you’ll run into this)