Getting Segmentation Fault on recovery It's an Android 4.0.3.
I'm trying to fix my tablet, because it doesn't start anymore.

running fastboot devices returns nothing.

Then, I'm trying to do that through adb.
adb devices returns 

List of devices attached
20080411        device


So I guess adb should be working, but when I try this I get a segmentation fault:

adb shell 
recovery 


I already tried many varations of button pressing on powerup, but nothing seems to work.

Any idea on how to fix it?
fastboot is when you enter fastboot mode, by powering up with volume up key pressed. Then fastboot devices would work.

Why are you invoking the recovery on its own via adb shell? 

The recovery binary is reliant on the startup scripts used within the recovery partition unless the partition is messed up.

Recovery only works by powering up with volume down key pressed at the same time.

The vital details are missing from the question. :)


What device are you trying to fix up in respect to getting into recovery? 
How did it happen? What did you do?