@leo provided specific instructions in his Salt tutorial on how to install an incremental back-up system with salt ; using the back-up tool Wyng written by @tasket. (Thanking you both btw).
0.3.15 is not marked as beta (lacking native encryption compared to >v4 but encryption strategies for v3 in Qubes are given in its readme)
I don’t know Tasket leitmotiv in writing a custom dedup backup tool, knowing the existence of Restic and Borg project. Some technical advantages have been exposed by himself here.
The exclusivity of this project is also himself also working on integration with Qubes ; we probably won’t find in other tools.
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Could Restic and/or Borg or other more mature tools follow the same Qubes integration strategy as Wyng ? Could this be adapted to Leo’s back-up salt tutorial ?