Tvheadend

Can anyone help with make muxdump of my local multiplexes from shell?

I have a FreeView from Crystal Palace and few other local transmitters ...
and would like to take a mux sample lets say of 200MB on each multiplex.

I have 3 tuners:
Bus 003 Device 003: ID 2013:025f PCTV Systems
Bus 003 Device 002: ID 2013:024f PCTV Systems nanoStick T2 290e
Bus 003 Device 005: ID 2013:024f PCTV Systems nanoStick T2 290e