1. first enter this command in your terminal
2. a file /etc/sudoers.tmp will open with your default text editor. i am running Ubuntu OS and nano is the default text editor in ubuntu
now find the following line
3. and add ,pwfeedback at the end of that line so that it looks like this
4. now press Ctrl+O (to save file) and hit enter then press Ctrl+X to exit the editor.
Note: step 4 depends upon your default editor (nano in this case)
In mac the default editor happens to be vim. so vim users may need to learn a few vim editing basics.