Different graphic cards drivers while booting from external media

Question

I am booting a certain system of mine with ubuntu 9.10 from external HDD. I am satisfied with the setup and it works fine, however I would like to modify it so that I can choose which graphic card drivers to load during the boot time. Specifically I would like to choose between:

• nvidia proprietary driver
• ati proprietary driver
• generic driver

Currently if I am using proprietary drivers then dont boot into X, delete xorg.conf, start gdm and reconfigure the system using jockey (for hardware drivers).

What would be the steps to make this (semi-)automatic and avoid restarting X?

Where could one find examples of such scripts?

Answer 1

1. Make 3 different grub entries for each kernel with driver1, driver2, driver3 as options.
2. Make 3 different xorg.conf (each with one of the three drivers) and name them xorg.conf1, xorg.conf2, xorg.conf2.
3. Write initscript that executes before X that greps /proc/cmdline for driver1, driver2 oder driver3 and then symlinks xorg.conf1, xorg.conf2 or xorg.conf2 to xorg.conf

I've done something similar to switch between dualheaded and not-dualheaded screensetup in the times before xrandr. Unfortunately the scripts and the documentation is long gone.

Possible improvements:

• use udev-rules
• let the initscript auto-detect the current graphics card

Answer 2

You could always make a shell script that automates that process for you.

Answer 3

The following might provide some hints at possibly achieving what you want via grub:

http://en.gentoo-wiki.com/wiki/Framebuffer

Answer 4

Create different versions of your xorg.conf based on the stuff you want. Say:

/etc/X11/xorg.conf.nvidia
/etc/X11/xorg.conf.ati
/etc/X11/xorg.conf.generic

Then configure multiple boot configurations in /boot/grub/grub.cfg and put a different kernel parameter (e.g. xconfig=myconfig) in every line where the kernel is specified. Somewhere along the lines of:

menuentry "Ubuntu, Linux 2.6.31-17 nvidia" {
  ...
  linux   /vmlinuz-2.6.31-17 root=UUID=885a6a07-fd6c-4638-aa17-d38997d477e1 xconfig=nvidia ro single
 ...
} 

menuentry "Ubuntu, Linux 2.6.31-17 ati" {
  ...
  linux   /vmlinuz-2.6.31-17 root=UUID=885a6a07-fd6c-4638-aa17-d38997d477e1 xconfig=ati ro single
 ...
}

menuentry "Ubuntu, Linux 2.6.31-17 generic" {
  ...
  linux   /vmlinuz-2.6.31-17 root=UUID=885a6a07-fd6c-4638-aa17-d38997d477e1 xconfig=generic ro single
 ...
}

Kernel parameters that aren't recognized are ignored, but will still be available in /proc/cmdline. Based on this, you can write a small shell script that chooses the correct config file:

#!/bin/bash
rm -f /etc/X11/xorg.conf
config=`cat /proc/cmdline |sed -e 's/.*xconfig=\([a-z]*\).*/\1/g'
ln -s /etc/X11/xonfig.conf.$config /etc/X11/xconfig.conf

Then put this somewhere in your boot order, before gdm starts.