Unfortunately this method does not discriminate between data destined for LAN or WAN addresses on eth0
You have to run tcpdump on the eth0 interface, exclude traffic sent to the LAN, and count the data
No one has been at the strip to fly, and neither the kiosk Pi nor access to the VRS has been used during lockdown, would you expect there to be a big difference between WAN/LAN in this case??
The LAN traffic would be a worse case scenario, with WAN traffic lower, so as a worst case, it covers the data requirement for a mobile broadband connection.
According to which and dpkg, tcpdump is not installed, so at that point, I defer to you and Keith and I stay away from apt-get to add it.
In order to avoid anything non standard on the ATOM, is it worth us asking nicely for a batch file that can be run to give simple data reports for you to lift via your secure network? Or have you already got this?
I'd possibly suggest a batch file running from cron/at for two days midweek, and another over the weekend, that would store the two numbers (RX/TX) in a file. Or alternatively, a weekly/monthly report to send to the station maintainer. The first avoids a processing overhead all the time.
If you are going to terminal, then you need to learn (for those who haven't) to pipe the output of a command to more or grep
pi@ognpaw:~ $ dpkg -l | more
or
dpkg -l | grep tcp
more means you only get one screen full until you press the space bar for the next screen.
grep takes the output of your command and filters it against the string specified after grep.