Starting with version 2.6, digiKam features the Tools → Maintenance menu which gives you access to tools designed to perform a variety of housekeeping tasks: from scanning for new photos to running a face recognition action. Here is a brief overview of the available tools.
Scan for new items This command scans the collections for newly added photos. By default, digiKam does that automatically on every start. But if you’ve disabled this feature to speed up digiKam, you can use the Scan for new items tool to add new photos manually.
Rebuild thumbnails If, for some reason, thumbnails in albums are missing or broken, you can use this tool to fix them. To speed up this action, enable the Scan for changed or non-cataloged items option. This will ignore photos which have already been processed and catalogued.
Rebuild fingerprints digiKam uses fingerprints for certain search actions, and this tool allows you to generate or rebuild fingerprints. Enable the Scan for changed or non-cataloged items option to skip the already processed and cataloged photos.
Find Duplicate Items Need to find duplicate photos? This command can help you with that. Note that this action uses fingerprints, so you might need to run the Rebuild Fingerprints action prior to using this tool.
Sync image metadata with Database When digiKam adds new photos, it automatically reads metadata from each photo and writes them into its database. The Sync image metadata with Database tool does the opposite: it reads metadata from the database and writes them into photos or into so-called XML sidecar files. This feature can come in handy in many situations. You can use it, for example, to back up metadata from the database to XML sidecar files.
Face Detection This tool finds photos containing faces and attempts to recognize person or persons in each photo. (see the Face Recognition article for more info.)