UPDATE: the following guide is useful if you are using Xorg 7.3 or previous versions. If you are using Xorg 7.4 there is a guide to configure two fingers scrolling on a regular synaptics touchpad if you are using Xorg 7.4 or superior.

One of the features I really love about Apple's notebooks is the two fingers scrolling enabled touchpad they have.

It's easier and faster to use than the regular side scrolling available on normal notebooks.

So.. I recently had a look at the synaptics documentation (synaptics is the driver which manages the touchpads under Linux).

Well.. After some reading and a bit of google searches it turns out that is possible to enable two fingers scrolling on recent synaptics touchpads even on normal/regular notebooks (not Apple Macbooks).

I've been able to enable this feature on my Toshiba Tecra A7 which is pretty new hardware but I've read success stories from people using 4/5 years old notebooks.

Following this guide you will get a two finger scrolling capable touchpad (on both X and Y axis - top-bottom, left-right), with simulated middle click on two fingers click and still lateral scrolling enabled.

This is how you can do this:

1. Locate your xorg.conf configuration file: it usually resides under /etc/X11/
2. Then do a backup copy of it! Just in case something goes wrong!
3. Login as root: without root permission you can't modify the xorg.conf file
4. Check using your distribution package manager that you have installed the synaptics Xorg driver. If you don't have it you should install it. The command here depends on the distribution that you are using. eg. under ArchLinux you can get it using pacman -Sy synaptics
5. open xorg.conf file with your favorite text editor (using the root account)
6. Locate the Module section and add the synaptics driver to the loaded modules:
   

   Section "Module"
   
   # .....
   # Just add the line below
   
   	Load  "synaptics"
   
   # Section continues ....
   
   EndSection
   

7. Add a new InputDevice section. Just insert the following code to your xorg.conf file:
   

   Section "InputDevice"
   	Identifier      "Touchpad"
   	Driver          "synaptics"
   	Option  "Device"        "/dev/input/mouse0"
   	Option  "Protocol"      "auto-dev"
   	Option  "LeftEdge"      "1700"
   	Option  "RightEdge"     "5300"
   	Option  "TopEdge"       "1700"
   	Option  "BottomEdge"    "4200"
   	Option  "FingerLow"     "25"
   	Option  "FingerHigh"    "30"
   	Option  "MaxTapTime"    "180"
   	Option  "MaxTapMove"    "220"
   	Option  "VertScrollDelta" "100"
   	Option  "MinSpeed"      "0.06"
   	Option  "MaxSpeed"      "0.12"
   	Option  "AccelFactor" "0.0010"
   	Option  "SHMConfig"     "on"
   	Option	"VertTwoFingerScroll"   "1"
   	Option	"HorizTwoFingerScroll"  "1"
   EndSection
   

   NOTE: The really important lines here are just

   	Option	"VertTwoFingerScroll"   "1"
   	Option	"HorizTwoFingerScroll"  "1"
   

   If you have one, you can keep your existing synaptic configuration and just insert the above two lines.

8. Remember to add the newly added InputDevice to the ServerLayout section. This is how it looks mine:
   

   Section "ServerLayout"
   	Identifier     "Simple Layout"
   	Screen      0  "aticonfig-Screen[0]" 0 0
   	InputDevice    "Mouse1" "CorePointer"
   	InputDevice    "Touchpad"  "SendCoreEvents"
   	InputDevice    "Keyboard1" "CoreKeyboard"
   EndSection
   

9. Well, you should have a working configuration now. Anyway.. you might find that horizontal scrolling (left-right) is pretty annoying while using Firefox. This is because the browser will go down and up in your browsing history (like pressing the "Back" button).

   You can disable this Firefox behavior simply inserting the about:config text on the address bar and opening it like a real URL.

   Then search and set the following configuration values as displayed:

   mousewheel.horizscroll.withnokey.action = 0
   mousewheel.horizscroll.withnokey.sysnumlines = true
   

10. Enjoy your two fingers scrolling!