According to the freedesktop documentation Thumbnail Managing Standard
. You can force nautilus to recreate the thumbnail if the mtime (modification time) in the thumbnail is lower than the mtime in the original file.

7. Detect Modifications

One important thing is to assure that the thumbnail image displays the
same information than the original, only in a downscaled version. To
make this possible we use the modification time stored in the required
'Thumb::MTime' key and check if it's equal the current modification
time of the original. If not we must recreate the thumbnail.

Example 2. Algorithm to check for modification.

if (file.mtime != thumb.MTime) {
recreate_thumbnail (); }

It is not sufficient to do a file.mtime > thumb.MTime check. If the user moves >another file over the original, where the mtime changes but is in fact lower than >the thumbnail stored mtime, we won't recognize this modification.

In order to achieve this... you can try with a little Nautilus-Script to set the mtime in the original file to the current time with the touch command.

1) Creating the script. Open a Terminal window Ctrl+Alt+T and type:

For Ubuntu 12.04 & 12.10

• nano ~/.gnome2/nautilus-scripts/Regenerate-Thumbnail

For Ubuntu 13.04 & above

• nano ~/.local/share/nautilus/scripts/Regenerate-Thumbnail

2) The content of the script.

#!/bin/bash



BAKIFS=$IFS

IFS=$'

'



for FILE in $NAUTILUS_SCRIPT_SELECTED_FILE_PATHS; do

      touch -m "$FILE"

done



IFS=$BAKIFS

To save the changes in nano.. Ctrl+O,Enter then Ctrl+X.

3) To make the script executable.

For Ubuntu 12.04 & 12.10

• chmod +x ~/.gnome2/nautilus-scripts/Regenerate-Thumbnail

For Ubuntu 13.04 & above

• chmod +x ~/.local/share/nautilus/scripts/Regenerate-Thumbnail

4) To test the script you can open nautilus, select a file(s), right click and go to Scripts > Regenerate-Thumbnail.

Hope this helps.