"vgaswitch" script to turn on/off discrete videocard under Linux.

gistfile1.sh

#!/bin/bash
# Place this file under /usr/local/bin/vgaswitch

# load module (without this module "vgaswitcheroo" isn't available on my system)
modprobe radeon

# switch
SWITCH=/sys/kernel/debug/vgaswitcheroo/switch
if [ $# -eq 1 ]; then
    if [ "$1" == "low" ]; then
        echo "Turning on low-power card."
        echo DIGD > $SWITCH
    elif [ "$1" == "high" ]; then
        echo "Turning on high-power card."
        echo DDIS > $SWITCH
    elif [ "$1" == "on" ]; then
        echo "Turning on unused card."
        echo ON > $SWITCH
    elif [ "$1" == "off" ]; then
        echo "Turning off unused card."
        echo OFF > $SWITCH
    elif [ "$1" == "st" ]; then
        cat $SWITCH
    fi
else
    echo "Commands: [low, high, on, off]"
    echo
    echo "Status:"
    cat $SWITCH
fi

gistfile2.sh

#!/bin/sh
### BEGIN INIT INFO
# Provides:          vgaswitch
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Power on second videocard to fix errors on shutdown.
# Description: Place this file under /etc/init.d/vgaswitch and run "update-rc.d vgaswitch defaults".
### END INIT INFO

# Do NOT "set -e"

# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin

case "$1" in
  start)
  ;;
  stop)
	/usr/local/bin/vgaswitch on
	;;
esac

:

https://01.org/linuxgraphics/gfx-docs/drm/gpu/vga-switcheroo.html