Fan control in Linux, the easy way:

Open a Terminal and type,

cd /etc/X11
sudo nvidia-xconfig --cool-bits=4

This will take effect after a restart.

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The following also works for Ubuntu 12.04 and 13.04

After installing the NVidia drivers, you can facilitate fan controlled cooling by adding Coolbits.

Coolbits is basically an optional NVIDIA X Server component that adds a slide bar to control GPU fan speed.

Edit /etc/X11/xorg.conf, by pressing Alt+F2 and typing gksu gedit /etc/X11/xorg.conf

Add Option "Coolbits" "4" under the Device section, and save the file.
For example,

Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 570"
Option "NoLogo" "True"
Option "Coolbits" "4"
EndSection

If there is more than one device, "Device1", "Device2", then you will need to add Option "Coolbits" "4" to each section. Note that you will need a cable plugged into each GPU for this to work (or tell the system to think that the cards are plugged in).

Restart the system and open NVIDIA X Server.
On the left hand side, under your GPU, 'GPU 0 - (GeForce GTX 570)' for example, you should see a Thermal Settings entry.
Click on it, scroll down, and accept the agreement. Once you do this you can directly control the fan speed by sliding the slide bar. You can also see the GPU temperature from there. I suggest you keep the temps below 70°C if possible.

NB. You must go into the NVidia X Server after every restart and set the Thermal Settings.
You also have to set PowerMizer to 'Prefer Maximum Performance'.


Installed the 313.30 (or similar drivers)? No xorg.conf file? No Problem. Let's build one:

Open a Terminal and Type gksu nautilus
Note down the access rights for /etc/X11. Change the rights to allow writing and deleting of the /etc/X11 file.
Open another Terminal and type nvidia-settings. When the NVIDIA X Server Settings window opens select nvidia-settings Configuration and Save Current Configuration. This should create ~/.nvidia-settings-rc. Close X Server.
In a Terminal type nvidia-xconfig to create your /etc/X11/xorg.conf file.
You can then edit the xorg.conf file as above, or from a Terminal type nvidia-xconfig -- cool-bits=4 to add fan control.
Undo the access rights you changed, restart your system, open X Server set the fan speed, and stay cool!

An open thread with discussion about COOLBITS can be found at COOLBITS
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FAQ's

HOW TO:
- Opt out of Beta Tests
- Ask for Help

On Ubuntu x64 16.04 LTS I installed a new driver (after deleting some files on my boot drive to free up space) and encountered the warning:
Unable to locate/open X configuration file, followed by the message 'New X configuration file written to '/etc/X11/xorg.conf'.
Not sure if that encluded the cool-bits=4 command or not so I just ran the 'sudo nvidia-xconfig --cool-bits=4' command again and was informed that the xorg.conf file was backed up and the new file written to. After a restart it worked.
____________
FAQ's

HOW TO:
- Opt out of Beta Tests
- Ask for Help