nvidia-installer log file '/var/log/nvidia-installer.log'
creation time: Sat Oct  3 00:38:23 2015
installer version: 340.29

PATH: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

nvidia-installer command line:
    ./nvidia-installer
    --ui=none
    --no-questions
    --accept-license
    --disable-nouveau

Using built-in stream user interface
ERROR: An NVIDIA kernel module 'nvidia' appears to already be loaded in your kernel.  This may be because it is in use (for example, by the X server), but may also happen if your kernel was configured without support for module unloading.  Please be sure you have exited X before attempting to upgrade your driver.  If you have exited X, know that your kernel supports module unloading, and still receive this message, then an error may have occured that has corrupted the NVIDIA kernel module's usage count; the simplest remedy is to reboot your computer.
ERROR: Installation has failed.  Please see the file '/var/log/nvidia-installer.log' for details.  You may find suggestions on fixing installation problems in the README available on the Linux driver download page at www.nvidia.com.