video driver - Restore xorg.conf file in Ubuntu 16.04LTS

Checking the content of /etc/X11 dir, I saw that xorg.conf file is missing. Is that normal? I only have xorg.conf.failsafe configuration file with the following lines:

Section "Device"
    Identifier  "Configured Video Device"
    Driver      "vesa"
EndSection

Section "Monitor"

    Identifier  "Configured Monitor"
EndSection

Section "Screen"
    Identifier  "Default Screen"
    Monitor     "Configured Monitor"
    Device      "Configured Video Device"
EndSection

Is, the one above, a correct configuration file? Or, I have to restore the xorg.conf file? If yes, how can I do that? The current driver used is:

sudo lshw -c display | grep driver
[sudo] password di michele: 
       configuration: driver=i915 latency=0

and

lspci | grep -E 'VGA|Display|3D'

00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Whistler [Radeon HD 6730M/6770M/7690M XT] (rev ff)

A few hours ago, after rebooting my OS, I got a black screen with message:

your system is running in low-graphics mode

but after restarting the pc, all strangely returned as before.

Thanks!