this is an old topic, but still comes up in google search for "ubuntu gp2x", and with increasing adoption of linux as a desktop OS, i thought it might be relevant
firstly, you need to update to usb networking kernel module on your gp2x. the one that ships with it only works with 2.4.x kernels, and most linuxes these days run 2.6.x
to do this, grab a g_ether.o from any 2.6.x distro or kernel.org, or one is provided
here. make a file on your gp2x called usbnet.gpu, and put this in it:
CODE
#!/bin/sh
rmmod g_ether
cp -f g_ether.o /lib/modules/2.4.25/kernel/drivers/usb/gadget/g_ether.o
sync
modprobe g_ether
cd /usr/gp2x
exec ./gp2xmenu
then run it. this will update your gp2x. plug it in, turn on usb networking, run
ifconfig usb0 up 192.168.0.1 or whatever ip address is relevant on your pc, and you should be able to communicate with gp2x
(yes, this is all ripped straight from this wiki page, but is helpful for google searchers, or if the wiki page is down)
now i'd done all this on my laptop, and gp2x was working fine, but i couldn't get it going on my desktop pc. turns out it was the hardware in the pc causing the issue. specifically, i have a motherboard with an nForce chipset, which i found out (by googling "ubuntu nforce usb") is not very good at detecting usb devices under current (2.6.20) linux kernels. i first suspected it was something beyond the gp2x when none of my usb card readers would detect over 1gb, even though i was using known working 2gb/4gb/8gb sd and cf cards
my solution in this case was to install a pci usb2 card with a different chipset (via in my case, though any would do), now all my card readers detect fine. still no gp2x tho, i'm guessing there are still kernel issues with that
i hope someone finds these experiences helpful