Well, apparently the backups are created by GBAK.

but this is what is happening:

C:\Program Files (x86)\Firebird\bin>gbak -c -v -user SYSDBA -password masterkey c:\temp\retdata.bak c:\temp\test.fdb
gbak: opened file c:\temp\retdata.bak
gbak: cannot open backup file C:\temp\test.fdb
gbak: Exiting before completion due to errors

In the manual it says that the destination db must not exists, and it doesn't. In addition, why does it refer to the destination path as the backup file?

once again, thanks for your help.