Since 2015 Restic supports backup of databases (mysqldump, pgdump, etc), full devices (dd if=/dev/sda), snapshots (BTRFS send, LVM, ZFS), tar files, etc... using stdin option which is quite useful stated the amazing de-duplicaton restic uses.

Even if nothing in the database or the snapshot has changed, the dump to a file will always change, but using the stdin restic is able to differentiate when the data is the already stored or is new.

Stated all above, I would like to suggest to include the possibility of launching backups using directly stdin option of restic.

I can understand is not an easy task, since the complexity of using external services/devices out of the control of backrest, we add another layer of complexity in case of a docker version. I suggest could be managed by using hooks though.

I must say I used both the docker and the binary version of backrest, and I have already played with the possibility of using Hooks/scripts/pipes to send the output of btrfs send or mysql dump to backrest but unfortunately, I did not manage.

If in docker we can launch commands to the host from the docker image maybe we can think about something similar and use pipes (mkfifo) devices to "listen" on the stdin, and then store the data in restic.

I understand there are maybe other priorities but to help with the investigations I've just suggested few things and I bought few coffees since it's the only I can provide also I'm open to test if required.

let me know your point of view.