我从 12.04 升级到 13.10，之后，我的辅助显示器不再工作了。
多一点信息：
$ xrandr -q
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 1280 x 1024, maximum 1280 x 1024
default connected 1280x1024+0+0 0mm x 0mm
1280x1024 0.0*
1024x768 0.0
800x600 0.0
640x480 0.0
$ lspci | grep VGA
01:00.0 VGA compatible controller: NVIDIA Corporation GF114 [GeForce GTX 560 Ti] (rev a1)
$ sudo lshw -C video
*-display UNCLAIMED
description: VGA compatible controller
product: GF114 [GeForce GTX 560 …