Fatal: Couldn't open display :0

root     32085  0.9  1.9  26660  7488 tty7     Ss+  11:26   0:01 /usr/bin/X :0 -core -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch

root@zhumarin:/home/azq2# xrandr -d :0
No protocol specified
Can't open display :0

root@zhumarin:/home/azq2# export DISPLAY=:0
root@zhumarin:/home/azq2# compiz
compiz (core) - Info: Loading plugin: core
compiz (core) - Info: Starting plugin: core
No protocol specified
compiz (core) - Fatal: Couldn't open display :0
compiz (core) - Info: Stopping plugin: core
compiz (core) - Info: Unloading plugin: core

root@zhumarin:/home/azq2# xrandr -d /var/run/lightdm/root/:0
Can't open display /var/run/lightdm/root/:0