Migrate from Linux to Mac

[Maik Qualmann]

Why not simply migrate the MySQL database to SQLite on the Linux machine using 
the tool built into digiKam? Copy the database to the Mac and adjust the base 
path using the update function in the digiKam collection settings – done.

Regarding grouping settings in XMP, these are not available there.

It's difficult to save and restore them in XMP. Image IDs cannot be used because 
they will never be the same during scanning. It would have to be a path or a 
unique hash. But what if the group leader hasn't even been captured by the 
scan yet and is still unknown, etc.?

Maik

Am Mittwoch, 12. November 2025, 15:37:29 Mitteleuropäische Normalzeit schrieb 
Gilles Caulier:
> Hi,
> 
> The group definitions are stored in the digiKam database. If the group
> is stored as duplicate in the XMP sidecar, the group restoration must
> be transparent. I think that it's not the case (i don't remember doing
> it in the past). Perhaps Maik can second me here...
> 
> Anyway, the digiKam XMP namespace does not contain anything about
> group properties :
> 
> https://exiftool.org/TagNames/XMP.html#digiKam
> 
> If group properties must be stored in XMP, it must be by priority in
> the digiKam namespace (where we can do what we want), and in second to
> another XMP standard XMP namespace, if these properties exist and are
> not proprietary (a.k.a photoshop for ex.).
> 
> In the database the group properties will define the list of joined items.
> 
> A script can help to restore/patch the properties in the database. The
> schema is documented here :
> 
> https://invent.kde.org/graphics/digikam/-/blob/master/project/documents/DBSC
> HEMA.ODS?ref_type=heads
> 
> if i'm not too wrong the table is this one:
> 
> Table « ImageRelations »
> 
> NAME    TYPE    DESCRIPTION    READ FROM    WRITTEN  TO    CHANGED BY
> subject    INTEGER FOREIGN KEY
> object    INTEGER FOREIGN KEY
> type    INTEGER
> 
> So the item grouping uses the item ID in the database, not the file
> path. When you create a new database by importing the collections to a
> new computer, file and sidecar are parsed to restore the properties.
> Each item imported in the new database will use a new ID, which will
> break the grouping feature. And as the grouped item list is not stored
> in XMP...
> 
> Voilà for a quick interpretation of the problematic (without double
> check in the source code).
> 
> Best regards
> 
> Gilles
> 
> Le mer. 12 nov. 2025 à 13:54, Willem Boers <wboers at xs4all.nl> a écrit :
> > I am currently using DigiKam on a Ubuntu Linux PC using the local MySQL
> > Server on this machine. All collections (>100k photo and video files) and
> > the database are on a SSD on this PC. I use sidecar XMP files to store
> > metadata for all RAW files and video files and I am only using the basic
> > DigiKam functions for tagging and labeling (no RAW processing, editing or
> > face recognition) The Linux PC will be deprecated and I want to migrate
> > everything to my Apple Mac mini. I have done some tests and it appears
> > that DigiKam is working perfectly well on my Mac even with SQLite. I have
> > copied all collection folders from the Linux PC to the Mac and used
> > Tools->Maintenance-> Sync Metadata and Database on the Mac to try to
> > rebuild the database (now SQLite) from the metadata in the photo and XMP
> > files. As far as I can tell most data has been recreated except for the
> > group definitions (I have lots of groups for JPG-RAW combinations,
> > panorama photos, time series etc.) My questions:
> > - Can the group definitions be recovered from the Linux PC and added to
> > the Mac? - Are there other relevant features besides the group
> > definitions that may not have been recreated from the metadata in the
> > files? - Was this a proper way to transfer everything from the Linux PC
> > to the Mac or should I have used another method?