Repo sync with Internxt's WebDAV and its file's comparision criteria

[JanickGers85]

Hello everyone,
I'm well aware of repo rcloning and all the issues it can bring, as written here
https://borgbackup.readthedocs.io/en/stable/faq.html#can-i-copy-or-synchronize-my-repo-to-another-location
...so clarified that, here the question 😄

Internxt's WedDAV user as file comparison criteria the file path / filename and the file size; I've managed to make their WebDAV works (and it was not that easy...) but I'm asking if that criteria can bring to a corrupted synched Borg repository.
Reading the documentation and peeking into rclone logs:

• segments (i.e. files into the data/# folders) are never modified, so just created and deleted
• all transactional file has an extension with the transaction number, which is always different after any backup run
• I've not spotted modified files, just deleted or new files

So, is it safe to rely on that system that use that criteria to know if a file has been modified?

[ThomasWaldmann]

Just the filename and file size is a bit poor for a "sync" process, usually there is at least a timestamp or a checksum that's also considered.

For the borg segment files it would work, maybe also the repo index and hints file.

The repo config might be a problem though, e.g. if you change the repokey passphrase or append-only between 0 and 1, the config size might not change although the config is different.

The config file is NOT modified btw, borg rather writes a new config file to a temp filename and then atomically moves the temp file over the existing config. But if the sync process only checks filename and size, that does not help...

[JanickGers85]

Thanks for your reply @ThomasWaldmann.

Reading deeply rclone's documentation I've discovered this that seems to be the solution
https://rclone.org/docs/#u-update

Since Internxt's WebDAV implementation do not support the modification times nor checksums I can use the --update parameter during the sync: in this way the upload time will be used, and seems to be solution in my case (I'm doing daily backup and subseguent sync if borg check is successful).
I did some test and seems working.

I would greatly appreciate knowing your opinion as a maintainer of Borg.

[ThomasWaldmann]

The docs you link read confusing and I am not familiar with these options, nor with rclone and webdav, so you better carefully determine if it works as it should.