Snapshot in Firefox in Linux
 

How to do it?
This addon does not support Linux platform,
https://addons.mozilla.org/en-US/fir...ddon/fireshot/

Any solution?

You mean a screen shot? Push the print screen button

or
the way harder way , using Gimp
open gimp and file > create > from screenshot

I don't want to screen shop the who page, but just a portion of it.

there is a just a section on the gimp dialog

The addon is Screenshot Gimp,
installed and work, fine, :D

Although I don't use ubuntu, I use mint which is based on it and the screenshot tool gives you the option of either taking the whole page or a selection. You even have a timer which will take a snap after a specified number of seconds. Choose whichever you want.