Write-only mode (do not read anything from the remote)

[piegamesde]

Have you checked borgbackup docs, FAQ, and open Github issues?

Not extensively

Is this a BUG / ISSUE report or a QUESTION?

QUESTION (Feature request)

System information. For client/server mode post info for both machines.

Your borg version (borg -V).

Not installed

Operating system (distribution) and version.

Arch Linux

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I've got a simple-sounding feature request: Add a write-only mode, where backing up the data will not read anything from the repository (that has been encrypted). This will probably be like the append-only mode, but even more restrictive: No pruning, compaction and other things like this. I am fine if this will require parts (or the whole) of the database to be cached locally.

Why might one want such a thing, you might ask? Limiting the read access will pave the path of asymmetric encryption and scheduled backups without storing any passwords. I hope asking for this first will focus the discussion of this feature more on the technical aspects, since #672 went pretty off-topic and #120 was closed for being too broad.

[RonnyPfannschmidt]

from my understanding this is completely incompatible with the current design of borgbackup

[piegamesde]

How much reading is needed to perform the most basic backup operation? If the write-only happens for the actual data but reading of metadata is needed this could still go fine.

[ThomasWaldmann]

In any case, a backup needs to read/modify/write the manifest.

If the chunks cache is out of sync, it needs to read metadata of all missing archives.

[piegamesde]

Assuming the cache is in sync, is anything else read except for the manifest?

[ThomasWaldmann]

BTW, answer depends a bit on "by whom". IIRC, from code above the repo api, there is nothing else read. But the repository code itself might read/check more, e.g. for transaction processing. But you can easily try that yourself if you want to dig in that deep.

[piegamesde]

If we set potential asymmetric encryption as our end goal, every read action is problematic, independently of who does it.

[ThomasWaldmann]

Related: #1165

[ThomasWaldmann]

PR #8844