rdiff-backup (2.0.5-2) unstable; urgency=medium The network protocol of versions 1 and 2 of rdiff-backup are incompatible. This means that you must be running the same version (either 1 or 2) of rdiff-backup locally and remotely. Since Buster ships version 1.2.8 and Bullseye ships version 2.0.5, upgrading only the local system or only the remote system from Buster to Bullseye will break rdiff-backup runs between the two. For conveniency, version 2.0.5 of rdiff-backup is available in the buster-backports distribution, see https://backports.debian.org/ This allows to first upgrade only the rdiff-backup package on Buster systems, and then independently upgrade systems to Bullseye at your convenience. -- Samuel Thibault Sun, 27 Jun 2021 22:47:12 +0200