The local database

This page describes the local database associated with a backup

Duplicati uses two databases, one for the Server and one for each backup. This page describes the overall purpose of the local database and how to work with it. The database itself is stored in the same folder as the server database and has a randomly generated name.

If you have access to the backup files generated by Duplicati, you only need the passphrase to restore files. As described in the migration section, it is also everything that is needed to continue the backup. But to increase the performance and reduce the number of remote calls required during regular operations, Duplicati relies on a database with some well-structured data.

The database is essentially a compact view of what data is stored at the remote destination, and as such it can always be created from the remote data. The only information that is lost if the database is recreated are log messages and the hashes of the remote volumes. The log messages are mostly important for error-tracing but the hashes of the remote volumes are important if the files are not encrypted, as this helps to ensure the backup integrity.

Prior to running a backup, Duplicati will do a quick scan of the remote destination to ensure it looks as expected. This check is important, as making a backup with the assumption that data exists, could result in backups that can only be partially restored. If for the check fails for some reason, Duplicati will exit with an error message explaining the problem.

For some errors it is possible to run the repair command and have the problem resolved. This works if all data required is still present on the system, but may fail if there is no real way to recover. If this is the case, there may be additional options in the section on recovering from failure.

In rare cases, the database itself may become corrupted or defect. If this seems to be the case, it is safe to delete the local database and run the repair command. Note that it may take a while to recreate the database, but no data is lost in the process, and restores are possible without the database.