Nouveau & nvidia-drivers switching

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This article describes how to switch between NVIDIA's binary driver and the open source nouveau driver.

Switching using two kernels

On boot

This method assumes the following:

  • Two kernels, one with the nouveau driver enabled and one with the nouveau driver disabled (or built as a module).
  • The nouveau-less kernel needs to have a -nvidia suffix.
  • The GRUB bootloader.

It is assumed the system already has a nouveau kernel and want to build the one that will use the NVIDIA driver. Begin with appending the -nvidia suffix to the kernel name:

KERNEL 
General setup  --->
    (-mykernel-nvidia) Local version - append to kernel release

Now make sure the nouveau driver is disabled or built as a module:

KERNEL 
Device Drivers  --->
    Graphics support  --->
        <*> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)
        <M> Nouveau (NVIDIA) cards

Now recompile and install the kernel. Make sure to update GRUB to take the new kernel into account. Note that kernels with the same version but with different names are considered unique. To emerge an out-of-tree kernel module to be used with the nouveau kernel, first, copy over the nouveau kernels config file to /usr/src/linux/.config.

FILE /etc/portage/make.confSet VIDEO_CARDS to nvidia nouveau
VIDEO_CARDS="... nvidia nouveau ..."

After setting or altering VIDEO_CARDS values remember to update the system using the following command so the changes take effect:

root #emerge --ask --changed-use --deep @world

Blacklist the nvidia and nouveau modules to block udev from autoloading them.

root #echo -e "blacklist nouveau\nblacklist nvidia" >> /etc/modprobe.d/nvidia-n-nouveau.conf

And finally use the local.d script below to switch graphics driver depending on what kernel is booted:

FILE /etc/local.d/nvidia.start
#!/bin/bash

depend() {
	need localmount
	before xdm
}

if [[ $(uname -r) == *-nvidia ]] ; then
	modprobe -q nvidia
cat > /etc/X11/xorg.conf.d/01-nvidia.conf << EOF
Section "Device"
  Identifier   "Device0"
  Driver       "nvidia"
  Option       "NoLogo" "True"
EndSection
EOF
else
	modprobe -q nouveau
	if [ -f /etc/X11/xorg.conf.d/01-nvidia.conf ] ; then
		rm /etc/X11/xorg.conf.d/01-nvidia.conf
	fi
fi

Copy it to /etc/local.d/nvidia.start and set the executable bit:

root #chmod +x /etc/local.d/nvidia.start

Switching using a single kernel and hprofile

Another method is switching between two profiles with hprofile, using a single kernel: /etc/init.d/hprofile has to be modified adding a few lines for VGA switching. Warning: hprofile shall be added in boot runlevel.

Switching using a single kernel and systemd

If the system is configured to use systemd, control setting nvidia and nouveau by using the functionality provided by the kernel command line.

Note
The GRUB menu items shown are for demonstrating the changes to be made. Do not just copy and paste them verbatim into grub.cfg.

Within the grub.cfg file, duplicate the desired menu item and then edit the two versions to specify which modules with be blacklisted, and to pass an environment variable to systemd. If nvidia or nouveau modules were previously blacklisted in /etc/modprobe.d, then remove that configuration since that will now be controlled directly from the kernel command line.

FILE /boot/grub/grub.cfgBefore:
menuentry 'Gentoo Linux' {
        root=hd0,1
        linux /boot/bzImage root=PARTUUID=11111111-2222-3333-4444-555555555555 init=/usr/lib/systemd/systemd console=tty1
}
FILE /boot/grub/grub.cfgAfter:
menuentry 'Gentoo Linux - Nouveau' {
        root=hd0,1
        linux /boot/bzImage root=PARTUUID=11111111-2222-3333-4444-555555555555 init=/usr/lib/systemd/systemd console=tty1 modprobe.blacklist=nvidia systemd.setenv=GPUMOD=nouveau
}

menuentry 'Gentoo Linux - Nvidia' {
        root=hd0,1
        linux /boot/bzImage root=PARTUUID=11111111-2222-3333-4444-555555555555 init=/usr/lib/systemd/systemd console=tty1 modprobe.blacklist=nouveau systemd.setenv=GPUMOD=nvidia
}

Next, create a small script similar to the one shown in the "Switching using two kernels" section. It is very similar, but slightly modified. For the sake on continuity, place it in the same location. The main difference is that is does not use the kernel's name to determine which profile to use, but rather it uses a variable set in the environment by systemd from the kernel command line.

FILE /etc/local.d/nvidia.startOpenGL
#!/bin/bash

if [[ "$GPUMOD" == "nvidia" ]] ; then
cat > /etc/X11/xorg.conf.d/01-nv.conf << EOF
Section "Device"
  Identifier   "Device0"
  Driver       "nvidia"
  Option       "NoLogo" "True"
EndSection
EOF
else
cat > /etc/X11/xorg.conf.d/01-nv.conf << EOF
Section "Device"
  Identifier   "Device0"
  Driver       "nouveau"
EndSection
EOF
fi

As mentioned in the previous section, don't forget to set the executable bit.

root #chmod +x /etc/local.d/nvidia.start

To have this script get called during the systemd init process, create a service file for it, but it's just as effective to integrate it into the currently existing xdm, gdm, sddm or other(?) display manager service file. Do not edit the service file directly, since that will get overwritten the next time that package is merged that the service file belongs to. Instead, create an override for the service file, placed in the /etc/systemd/system/service-name.d/ directory.

So for example when using the sddm.service, create the directory /etc/systemd/system/sddm.service.d and place a file in it with a .conf file extension. Add a [Service] section that has an entry for ExecStartPre to call nvidia.start before sddm itself is started.

root #mkdir /etc/systemd/system/sddm.service.d && touch /etc/systemd/system/sddm.service.d/nv.conf
FILE /etc/systemd/system/sddm.service.d/nv.confActual contents may vary
[Service]
ExecStartPre=/etc/local.d/nvidia.start


Switching using a single kernel in an Optimus system without reboot

In an Optimus system, the graphics is handled by the Intel integrated card, while the user can choose to run specific programs with the NVidia dedicated card. This means that the modules handling the NVidia card can be safely force-unloaded and reloaded without reboot.

Follow the steps in the NVIDIA/Bumblebee page, and then add the nouveau flag to VIDEO_CARDS:

FILE /etc/portage/make.confSet VIDEO_CARDS variable for Optimus
VIDEO_CARDS="intel nvidia nouveau"

Then update the system using the following command so the changes take effect:

root #emerge --ask --changed-use --deep @world

Also, Bumblebee should NOT start on boot:

root #rc-update del bumblebee default

Then, follow the steps at https://wiki.freedesktop.org/nouveau/Optimus/. In short, list the available providers (which are the video cards):

user $ xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x8a cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 2 outputs: 2 associated providers: 1 name:Intel
Provider 1: id: 0x66 cap: 0x7, Source Output, Sink Output, Source Offload crtcs: 2 outputs: 5 associated providers: 1 name:nouveau

The exact output will differ for each system, but the important parameter is name. Then, define which card should be used for offloading:

root #xrandr --setprovideroffloadsink nouveau Intel

This will set Nouveau for offloading the Intel card. Replace the names nouveau and Intel with the names shown before.

After reboot, the system should be using Nouveau to handle the cards. The following script can be used to switch between nouveau and nvidia-drivers:

FILE /usr/bin/nvgraphicswitch
#!/bin/sh

Driver="$1"

/etc/init.d/bumblebee stop
rmmod -v -f nouveau
sleep 1

if [ "${Driver,,}" == nouveau ]; then
    modprobe -q nouveau

elif [ "${Driver,,}" == nvidia ]; then
    /etc/init.d/bumblebee start;

else
    echo "Choose a graphics driver [nouveau or nvidia]."
fi

Make it executable:

root #chmod +x /usr/bin/nvgraphicswitch

Testing:

root #nvgraphicswitch nouveau
user $ DRI_PRIME=0 glxinfo | grep "OpenGL vendor"
OpenGL vendor string: Intel Open Source Technology Center
user $ DRI_PRIME=1 glxinfo | grep "OpenGL vendor"
OpenGL vendor string: nouveau
root #nvgraphicswitch nvidia
user $ primusrun glxinfo | grep "OpenGL vendor"
OpenGL vendor string: NVIDIA Corporation
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