HOWTO: Create a boot option for easy dual to single display switching

Purpose

So the first question you might have is what is the point of this? Well, this procedure that will be outlined below is intented for laptop users who use their laptop in multiple setups. For instance, I am a Grad student at my local university and I have some lab space where I set my laptop up to have an additional monitor. But in all other locations that I use my laptop I will generally use just the laptop display. Instead of having to go to my nvidia-settings and changing it through that utility everytime I can just select the appropriate boot option in grub and let the script do that tedious bit of work.

Note

Although doing this procedure has a relatively low risk factor, you are doing this AT YOUR OWN RISK. Be smart back up important files.

Runscript

Below is the runscript that will be used in this procedure. It will be given the file name "xdisplay"; however, you can name it whatever you like so long as it does not overwrite an existing file in your /etc/init.d/ folder

File: /etc/init.d/xdisplay

#!/sbin/runscript
# To be placed in /etc/init.d/
# Run Command: rc-update add xdisplay boot

depend()
{
   need localmount
   before xdm-setup
   before xdm
   before alsasound
}

start()
{

   cmdline_display_mode_exist=$(cat /proc/cmdline | grep "display=")
   display_mode_dual_exist=$(ls /home/aether/conf/xorg/ | grep "xorg.conf.dual")
   display_mode_single_exist=$(ls /home/aether/conf/xorg/ | grep "xorg.conf.single")
   cmdline_display_mode=$(cat /proc/cmdline | awk -Fdisplay= '{print $2}' | awk '{print $1}')
   if [ -n "$cmdline_display_mode_exist" ]; then
      if [ -n "$display_mode_dual_exist" ] && [ -n "$display_mode_single_exist" ]; then
            #Choose the xorg file to be copied over
            if [ "$cmdline_display_mode" == "dual" ]; then
               ebegin "Configuring X display in TwinView mode"
               cp /home/aether/conf/xorg/xorg.conf.dual /etc/X11/xorg.conf
            else
               ebegin "Configuring X display in Standard mode"
               cp /home/aether/conf/xorg/xorg.conf.single /etc/X11/xorg.conf
            fi
         sleep 5
         eend 0
      else
         ebegin "Xorg file missing. Exitting"
         eend 0
      fi
   fi

}

Procedure

So here is what you will need to do to get this to work. This procedure assumes you are currently root.

STEP 1

Make a file that contains the above code. I called this file "xdisplay"

STEP 2

Make two versions of your xorg.conf file; one for single display and one for dual display configuration.

These should be named "xorg.conf.single" and "xorg.conf.dual" respectively.

If you don't know how, best read up cause this isn't the topic of discussion.

STEP 3

Place these in some logical place on your local disk.

In my case, I place them in ~/conf/xorg/

STEP 4

Edit the file that contains the above code to point to those two files.

I.e. Replace all occurances of this path:

/home/aether/conf/xorg/

with the path where those two xorg.conf files are located.

An easy command can do this for you, replacing <YOURPATH> with the full path to the two xorg.conf files you just created:

sed -i "s_/home/aether/conf/xorg/_<YOURPATH>_g" xdisplay

STEP 5

Now, as root, move xdisplay (if not already) to:

/etc/init.d/

STEP 6

Add this to rc-update list. Use the following command as root:

rc-update add xdisplay boot

STEP 7

As root edit your grub menu.lst

vim /boot/grub/menu.lst

or

gedit /boot/grub/menu.lst

STEP 8

Add two more sabayon sections. Just make two copies of your existing one that you normally boot from.

In one case you add the flag:

display=dual

In the other case you add the flag:

display=single

Technically it doesn't matter what you have after "display=" in this case as it default to single if dual is not satified

STEP 9

I suggest you keep your existing section you boot from as the default that way it only bothers copying the xorg files when you need to change modes.

Grub

Here is an example of my menu.lst after configuration

File: /boot/grub/menu.lst

# grub.conf generated by the Sabayon Linux Installer
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,4)
#          kernel /kernel-genkernel real_root=/dev/VolGroup00/LogVol00
#          initrd /initramfs-genkernel
#boot=sda
default=0
timeout=30
splashimage=(hd0,4)/grub/splash.xpm.gz

title Sabayon Linux (genkernel-x86_64-2.6.27-sabayon) (music)
root (hd0,4)
kernel /kernel-genkernel-x86_64-2.6.27-sabayon music root=/dev/ram0 ramdisk=8192 real_root=/dev/VolGroup00/LogVol00 dolvm  quiet  init=/linuxrc splash=silent,theme:sabayon CONSOLE=/dev/tty1 vga=0x369 resume=swap:/dev/mapper/VolGroup00-LogVol01
initrd /initramfs-genkernel-x86_64-2.6.27-sabayon

title Sabayon Linux (genkernel-x86_64-2.6.27-sabayon) (verbose)
root (hd0,4)
kernel /kernel-genkernel-x86_64-2.6.27-sabayon root=/dev/ram0 ramdisk=8192 real_root=/dev/VolGroup00/LogVol00 dolvm  quiet  init=/linuxrc splash=verbose,theme:sabayon CONSOLE=/dev/tty1 vga=0x369 resume=swap:/dev/mapper/VolGroup00-LogVol01
initrd /initramfs-genkernel-x86_64-2.6.27-sabayon

title Sabayon Linux (genkernel-x86_64-2.6.27-sabayon) (verbose) (dual)
root (hd0,4)
kernel /kernel-genkernel-x86_64-2.6.27-sabayon display=dual root=/dev/ram0 ramdisk=8192 real_root=/dev/VolGroup00/LogVol00 dolvm  quiet  init=/linuxrc splash=verbose,theme:sabayon CONSOLE=/dev/tty1 vga=0x369 resume=swap:/dev/mapper/VolGroup00-LogVol01
initrd /initramfs-genkernel-x86_64-2.6.27-sabayon

title Sabayon Linux (genkernel-x86_64-2.6.27-sabayon) (verbose) (single)
root (hd0,4)
kernel /kernel-genkernel-x86_64-2.6.27-sabayon display=single root=/dev/ram0 ramdisk=8192 real_root=/dev/VolGroup00/LogVol00 dolvm  quiet  init=/linuxrc splash=verbose,theme:sabayon CONSOLE=/dev/tty1 vga=0x369 resume=swap:/dev/mapper/VolGroup00-LogVol01
initrd /initramfs-genkernel-x86_64-2.6.27-sabayon

title Sabayon Linux (genkernel-x86_64-2.6.27-sabayon) (safe mode)
root (hd0,4)
kernel /kernel-genkernel-x86_64-2.6.27-sabayon root=/dev/ram0 ramdisk=8192 real_root=/dev/VolGroup00/LogVol00 dolvm init=/linuxrc CONSOLE=/dev/tty1 resume=swap:/dev/mapper/VolGroup00-LogVol01 nox acpi=off ide=nodma vga=normal
initrd /initramfs-genkernel-x86_64-2.6.27-sabayon

title Microsoft Windows Vista Ultimate
rootnoverify (hd0,2)
makeactive
chainloader +1

title Dell Diagnostics
rootnoverify (hd0,0)
makeactive
chainloader +1		
}

Optional Wallpaper Feature

If you'd like, you can also create a nice little script to accompany the above runscript. The script below automatically changes the wallpaper based off of which boot entry was chosen. When you log into gnome/kde (or other DE), this script will be run (by adding it to your "SESSIONS" Startup Programs in gnome, or "Autostart" folder in KDE). Just change the "src1" and "src2" variables to be equal to the path where the wallpapers are stored. Make sure you chmod this file as root issuing the command:

chmod 775 myWallpaper.sh

File: myWallpaper.sh

#!/bin/bash
cmdline_display_mode_exist=$(cat /proc/cmdline | grep "display=")
cmdline_display_mode=$(cat /proc/cmdline | awk -Fdisplay= '{print $2}' | awk '{print $1}')
dest="/desktop/gnome/background/picture_filename"
src1="/home/aether/conf/wallpaper/sabayonlinux-widescreen-plain-dual.png"
src2="/home/aether/conf/wallpaper/sabayonlinux-widescreen-plain.png"
if [ -n "$cmdline_display_mode_exist" ]; then
                        #Choose the wallpaper
                        if [ "$cmdline_display_mode" == "dual" ]; then
                                gconftool-2 -t str --set $dest $src1
                        else
                                gconftool-2 -t str --set $dest $src2
                        fi                                   
fi

Hope this is useful to some. Enjoy. Optionally you can go to [[1]] to see a forum discussion on this or post problems or concerns.

-Aether