eth0 file has file KIND of PNG image
 

I have a /var/lib/vnstat/eth0 file that has a KIND of PNG image and originally was unknown. How do I change this data file back to an unknown KIND?

??
How do you know it is a Portable networks graphics photographic image ?
if you do not know if it is even a png photograph

I see the file KIND in Xfce's Thunar and Nautilus Properties Menu. Also I use the "file" command to show its type of PNG instead of unknown.

The file command shows:

eth0: PNG image data, 12 x 12, 8-bit/color RGBA, non-interlaced

[SOLVED] eth0 file has file KIND of PNG image
 

The file is returned back to its orignal unknown KIND by opening the file in a text editor, e.g. gedit or leafpad, deleting the first line of "‰PNG" and savimg the file.