1. Follow the steps in the post to install the nvidia-331 nvidia-setting nvidia-prime
Http://jingyan.baidu.com/article/046a7b3efe8c58f9c27fa98b.html
2. Restart after the discovery of the graphical login interface (the screen has been flashing, a moment of black screen, a moment landing interface), even CTRL+ALT+F1 also received influence can not enter normally.
Only into recovery mode.
Note: If this is not the case, direct ctrl+alt+f1 into terminal mode, skip to step 6th
3. Restart the computer in the GRUB option, select Recovery Mode to edit by E, the second-to-last row of RO (read only) into RW (read and write), the system can be modified after entering the single user system. Then ctrl+x into recovery mode.
4. When the graphical interface appears, select the root option and log in as root.
5. If your/usr and/or not the same partition need to be mounted, or the system can not find a command such as: Vi,mount/dev/sda11/usr (my usr in the/DEV/SDA11 partition)
6. Now it's time to restore the video card:
1) How do you install Nvidia-prime, directly prime-select Intel (choose Intel Driver) on it, do not appear wrong words can reboot. Note: If GRUB does not change to RW when it is started, it cannot be modified on the line.
2) If the first step is not possible, proceed to scenario 2, i.e. follow the steps below: (Not verified)
A. cd/etc/x11
CP xorg.conf Xorg.conf.backup
RM xorg.conf (delete profile for NVIDIA graphics card)
b sudo apt-get remove--purge nvidiax (remove NVIDIA graphics card)
C. reboot
3) If not, take option 3 to reinstall the Unity Desktop System
You can refer to the following documents:
Uninstall: http://blog.csdn.net/thanklife/article/details/7207060
Installation: http://linux.cn/article-3074-1.html
4) How to still be able to solve the word, take the ultimate solution:
Re-assembly system
Ubuntu 15.04 installs the graphics driver, the login interface flashes the solution (Dell 3420)