How about migrating Thumbnails from Windows to Linux

Software darktable
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I migrated away from Windows to Ubuntu 24-04. Changed email, changed cloud storage, no Google, Microsoft or Adobe left. Happy!

Darktable does great. But - because I was experimenting a lot - I hesitated migrating my darktable files from Windows to Linux. I will shortly try to use the dt_move script. Maybe I will have to experiment a little - believe it will work alright after some trying.

But how about all thumbnails? It took me - for more than 100.000 pictures - two full days to produce them. I know where they reside, both under Windows and Linux. So I’d rather copy those over from Windows to Linux. But then I will probably brake some links between the originals and the thumbnails - or won’t I?

Has anybody experience doing this?

Kind regards Jetze

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@Jetze
First and main assumption : on Linux and on WindowsYou have the same database. Of course with Linux modifications.
mipmaps folder names are different on Windows and on Linux but content inside these folders are the same.
Thumbnail 1.jpg on windows is the same as thumbnail 1.jpg on Linux.

  1. Find where is mipmaps folder on windows.
  2. Find where is mipmaps folder on Linux.
  3. Copy folder Windows/mipmaps / 1 to Linux / mipmaps / 1
  4. Copy folder Windows/mipmaps / 2 to Linux / mipmaps / 2
  5. And so on
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Or don’t bother copying or pre-generating them: darktable will generate then as and when needed.

Downside is that browsing will be a lot less fluid for a while. Upside is you don’t waste time and disk space on thumbnails that may never be needed.

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Thanks a lot @DarekK for your reply,

The assumption is that the link between a picture in the darktable database and its thumbnail exists out of its number in the order in the database. I will just try this route first as I do believe my databases will be the same after using dt_move.

And when to no avail I will follow @rvietor 's advise and see if I can just generate the last year of previews and add to that the previews of pictures having the biggest chance of being edited (having a rate >1 and in my case a green label).

Kind regards,
Jetze

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In DT is panel “Image Info”,
There on top is field called “Img index” or something like this.
This number it is name of a jpg file in mipmaps folder.

If You have imgindex 1, that means name of thumbnail is 1.jpg. That is the link.
Simply open thumbnail 1.jpg (or 65535.jpg) in any image viewer and check if it is the same look as in dt.

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Thanks @DarekK ! Jetze