I wanted to decrease the dblock-size of an existing backup, but Duplicati 2.4.0.104_canary_2026-10-11 refused to do it and threw an error.
You have attempted to change the parameter “dblock-size” from “524288000” to “262144000”, which is not supported. Please configure a new clean backup if you want to change the parameter.
It is not possible to increase the size, too.
I believe this is present since 2.4.x.
Was there a change and I overread it in the changelog?
That is a side-effect of another fix. We store the dblock-size in the database so more bare-bones operations (from the commandline) knows these values without needing them explicitly supplied.
But the check for unsupported changes covers all values stored in the database this way, giving the error you report.
This will be fixed in a later version.
For now, if you want to change it, you can use the bundled database-tool to remove the row:
duplicati-database-tool execute "/path/to/XXXXXXXXXX.sqlite" "DELETE FROM [Configuration] WHERE [Key] = 'dblock-size'" --create-backup
Windows equivalent:
Duplicati.CommandLine.DatabaseTool.exe execute "C:\path\to\XXXXXXXXXX.sqlite" "DELETE FROM [Configuration] WHERE [Key] = 'dblock-size'" --create-backup
This will simply remove the persisted value and then write the new value on the next run.
Not that if you increase the dblock-size significantly then Duplicati will think the old volumes are “too small” and start compacting them into larger volumes on the next run.