user@home:~$ beryl
**************************************************************
* Beryl system compatiblity check                            *
**************************************************************

Detected xserver                                : AIGLX

Checking Display :0.0 ...

Checking for XComposite extension               : passed (v0.3)
Checking for XDamage extension                  : passed
Checking for RandR extension                    : passed
Checking for XSync extension                    : passed

Checking Screen 0 ...

Checking for GLX_SGIX_fbconfig                  : passed
Checking for GLX_EXT_texture_from_pixmap        : passed
Checking for non power of two texture support   : failed

Support for non power of two textures missing
beryl: Another window manager is already running on screen: 0
beryl: No manageable screens found on display :0.0
user@home:~$