How can I sniff http credentials?

[eljach]

Hi guys. I just got my LAN Turtle, I was trying to sniff credentials over HTTP but I didn't find any module to do the job. The closest one to what I need is URLSnarf but it only logs the URLS of the request, is there a module to read the data of the requests? Or, Can I read the data of the request with URLSnarf? 

[Sebkinne]

TCP dump will work nicely.

[eljach]

16 hours ago, Sebkinne said:

TCP dump will work nicely.

But there is not any module for TCPDump in the Turtle. Should I launch the command manually in the shell? If that is the case, How can I launch the command every time I plug the turtle into a new computer?