Reasons for "WARNING: Cannot retrieve last file backup when doing incremental backup. Doing full backup now..."

Hello,

what can be a reason for
“WARNING: Cannot retrieve last file backup when doing incremental backup. Doing full backup now…”

Doing a full backup can be very time consuming -especially over the internet.
Can’t UrBackup revert to a previous incremental backup?

I am currently evaluating Urbackup locally, but the plan is to ‘preseed’ the backup-drive locally and then to send it to a relative, for an offsite backup.
Reverting to a full backup now means one day of backup again. When the disk is sent away, it esentially means sending it to me again, preseeding and sending it back.

Greetings,
Hendrik

I browsed the code a bit.
https://sourceforge.net/p/urbackup/backend/ci/6a3d0f60461131decc79a9a6b2c0a55edeccdd47/tree/urbackupserver/server_get.cpp#l1792

But basically It just confirms what the message says.

I think, the reason could be that the last incremental backup was not completed. But I don’t see that urbackup tries to find a previous incremental backup (or at least do an incremental on the last full backup).

Is that possible somehow?

Greetings,
Hendrik

Hendrik, what exactly is the issue here? Incremental backup is incremental of something, so it has to have a base. How can you have an incremental backup without having a full one?