你点ctrl+alt+f1切换登陆，输入用户名密码，然后
sudo nano /usr/share/xsessions/ubuntu.desktop
可以把内空改为下边的内容
[Desktop Entry]
Name=Ubuntu
Comment=This session logs you into Ubuntu
Exec=gnome-session --session=ubuntu
TryExec=unity
Icon=
Type=Application
X-LightDM-DesktopName=Unity
X-Ubuntu-Gettext-Domain=gnome-session-3.0
然后保存退出，重启试试
