Backup started failing "non-empty blocksets with no associated blocks"


Backup fail to start with error:
System.AggregateException: Detected non-empty blocksets with no associated blocks!

Not long ago I rebuild the database because of some errors. I am using

Should I rebuild again?

Fatal error: Detected non-empty blocksets with no associated blocks

This error is coming out of database VerifyConsistency step, but I’m not exactly sure how we’d get into this situation in the first place.

I’d suggest a Repair first (just because it’s likely faster) to see if that resolves it and if not then try another rebuild.


I just had the same error.

  • My backup was working great. It included a lot of directories, including “C:\user” and all subdirectories.
  • I deleted some source files from the backup set (via the ‘edit’ option). Specifically, I deleted a cache directory from deep within the windows c:\USER…\appdata\mozilla… tree (as it was just continually backing up new cache files pointlessly)
  • On the very next (and every subsequent) backup, I get the above error.
  • I tried editing the job again, and the strange part is that the changes I made to the directory selections didn’t seem to ‘stick’. Deleting the whole C:\user directory didn’t help, and adding it back didn’t help either.

It may be pure co-incidence, but my gut tells me that deleting directories from the source list is related to the error.

Fatal error: Detected non-empty blocksets with no associated blocks

Same issue here. I just did reset several terabytes of backups about two months ago due this error. Now it appeared again. Yet, after updating to latest duplicati there was positive development. Running repair actually fixed the issue. So I didn’t need to reset the backup set(s).

That’s great advancement that repair works. Even better would be that it wouldn’t need the manual running of repair. Automatic error detection and recovery is what I’m always looking for, if possible.

  • Thank you

Fatal error: Detected non-empty blocksets with no associated blocks

What does ‘stick’ mean? Changes only affect future backups, unlike on some other backup programs where deselection purges data. The PURGE command is a Duplicati do-it-yourself (for example with Commandline).

Was this trying to help the ‘stick’ or the error? Either way it may be because it doesn’t change existing things. The DELETE command is a way to delete entire versions of the file view. In the job, retention sets up deletes.

Any more test clues, anyone? I tested unchecking a source directory that had been backed up. All still works. There’s also a theory (pointing to this article actually) that privilege changes are involved in producing this…


@ts678 I am guessing that @T_C means deleting from the source list, not deleting from disk.


Agreed, and that’s what I translated into “deselection”, meaning take what was checked and click to uncheck. After that, things got less clear to me. I don’t think I wandered into on-disk deletions from source (don’t do it), however deletions from destination backup files (and their representation in the database) are key to the bug because it’s complaining about seeing files with non-zero lengths where it can’t find any blocks for the files… Version deletion can eventually take care of that (or sooner, if requested) by erasing memories of those files.

Fatal error: Detected non-empty blocksets with no associated blocks

I am also experiencing this problem. I have 2 backup tasks, one that is working perfectly fine. The other one is about 4x the size on disk and could never successfully finish because of this error. I have tried to run it twice, deleting all files on the remote between attempts. And both times it has failed with this error. As does it now, when I try to start it manually. I have tried database repair, which performed some deletions and completed successfully, but the error still prevents me from backing up this task.


If you still have the db (.sqlite file) can you perform the steps listed in this post. They’re pretty detailed, including downloading an sql browser program but it would really help characterizing the problem.