I have my Late 2013 Retina MacBook Pro attached to an external display. I use both displays. At night, when I leave my computer, I want to close the lid to put the Mac to sleep.
Since Lion, there is the famous 'Clamshell mode', which is for a lot of people, but not for me. This causes OS X to switch to single-display mode, using only the external display, if I close it.
Until Mavericks I could prevent this by the famous: sudo nvram boot-args="iog=0x0"
kernel parameter, but since Yosemite, this does not work. Is there any solution? I don't want to plug off my computer for the night or put it to sleep by selecting a menu command. Both solutions are really lame.