mediascanner on SD

[guru]

I copied to the SD some 70.000 files (OSM tiles to be used by uNav when tiles can't be fetched from Internet) and since then the gallery-app stoped presenting new fotos or screenshots. The reason is that some mediascanner is running in background and could not end up indexing all these files. One has to create a file with the name .nomedia in each directory to which the proc should not descend. Just as a hint.