Usually I'm a Win Vista user though, this is the ScreenShot on Ubuntu Studio 11.04.
Simply, plug APC20 and set Duplex's in&out ports.

[Note] About nanoKONTROL2:
It works on Ubuntu too. But if you want to use it for the bi-directional comunication, you should set nanoK2's LED mode to "External" by using the Korg's editor. I think this setting is not possible on the hardware only. So, you need Win or Mac just for the setting.
Also nanoK2 seems to send very accurate midi signals, therefore it tends to be cpu heavy a bit, I need more testing though.
Well, nanoK2 itself is interesting controller, and I like it too. 
Really nice ! That's a really complete answer. I've got an old g4 mac if needed (for nanokontrol). For renoise and more generally speaking, wich one will work better (or be more usefull, to be more specific) ? APC20 or launchpad ?
APC20 seems (if I understand correctly your answer) really USB compliant, so I should be able to use it with any linux music software, am I right ? For now I just do the math : launchpad + nanokontrok (the one with faders) cost more than the APC20. Since I'm on budget...
For now I'm using that kontroller :

I believe it will easily replace the mix features on the APC40. By the way, does Renoise got a soft takeover feature ? Since my DJ kontroller 's got 2d and 3rd level controls (you can punch select buttons, shift, etc...so the pads can be used for other fonctions, depanding if lights are on, off, or blinking). As far as I know, the only issue is that I cannot use the crossfader in any other software than MIXXX (not speaking of ableton, traktor and other expensive softwares I cannot afford, of course).
Seeing most of the DAW/midi software availables, a midi mixing controller (like the nanokontrol, or the faders part of the apc20) seems to be a must have. It's why I'm thinking of what would be the best to complete my KDJ500. For what I understood, I'd need a grid controller + a faders controller.
For now, I'm wondering about 3 different setups :
APC20
Launchpad + nanokontrol2 (but it's too expensive for now, honestly)
nanokontrol2+nanopad2 (=2x8 pads) (or any other cheap grid controller)
The main required features are : perfect fit for Renoise (and if possible, other linux programs)
Good addition to my current DJ MIDI control (KDJ500), especially for live performance
Budget (most important thing, I'm afraid)
Any other (cheap or cheaper) ideas will be appreciated
Many thanks
Edited by dem, 29 November 2011 - 12:23.