there is a feature request with a lot of good comments on their forum. The summary of the last time I checked it was on the lines: “it is a reasonable request but it is terribly hard to implement it correctly and since we currently have no capacity to do it we prefer leaving it not implemented instead of offering any alternative which could give a false sense of security”
I don’t have a testing environment, but essentially all my services are on docker saving their data in a directory mounted on the local filesystem. The dockerfile reads the sha version of the image from an env file. I have a shell script which:
if a new Docker version is broken rolling back is as simple as copying the old version in the env file and recreating the container. If data gets corrupted I can just copy the last working status from an old snaphot.
The whole os is on a btrfs volume which is snapshotted regularly, so ideally if an update fucks it up beyond recovery I can always boot from a rescue image and restore an old snapshot. But I honestly feel this is extra precaution: in years that I run debian on all my computers, it never reached the point of being not bootable.