[xubuntu-users] How do USB drives get automounted? (mine don't and I'm trying to work out why)

[Chris Green]

I have three xubuntu 11.10 systems running here, one is a 32-bit laptop
and two are 64-bit desktop machines.

USB drives plugged into the laptop and one of the dekstop machines get
automounted correctly but on the other desktop machine although the USB
drive is recognised (appears in dmesg as it should) it doesn't get
automounted. 

So how can I diagnose what's wrong or missing on the desktop machine
where the automounting doesn't work?  I think it's *possible* that I
have removed something necessary and/or misconfigured something as this
machine is quite heavily customised.

As I have a working machine and a non-working one I may be able to
compare things between the two machines to see what is wrong but I need
to know the sort of places I should be looking.

What processes and packages are involved in automounting a USB drive? As
I said it appears to be recognised correctly by the kernel, messages in
dmesg and syslog are the same on both the system where it's not
automounted and the system where it is. 

After the kernel has recongnised the USB device as a mass storage device
what then mounts it automatically and (if configured to do so, which it
is) pops up thunar?

Any/all help would be most welcome as this problem is getting really
annoying! 

-- 
Chris Green