ubuntu 登录界面无限循环问题解决方法

1. 卸载显卡驱动：
   参考：http://blog.csdn.net/ssmixi/article/details/73483795

2. 重新安装显卡驱动：
   (1) 在文本模式下重新安装显卡驱动：
   参考：http://blog.csdn.net/ssmixi/article/details/73483795
   若出现错误：
   ERROR：Unable to find the kernel source tree for the currently running kernel. Please make sure you have installed the kernel source files for your kernel and that they are properly configured on Red Hat Linux system, for exzmple ,be sure you have the ‘kernel-source’ or ‘kernel-devel’ RPM installed .If you know the correct kernel source files are installed ,you may specify the kernel source path with the ‘–kernel-source-path’ command line option.
   解决办法：sudo apt-get install linux-headers-generic
   （参考自https://zhidao.baidu.com/question/2115963192369533267.html）
   (2)登入桌面后终端安装显卡驱动：
   登录界面登录后重新安装显卡驱动：参考：http://tieba.baidu.com/p/4851231424