A graphical boot from BIOS to your Application

Intro

This article describes how to configure your Linux system to display an nice graphical image from the BIOS until your application or the login manager appear. No text should appear on the screen during that time.

The web is full with descriptions and tools that cover tiny parts of this process, however there seems to be no document that covers the whole path end to end. This document wants to do this and cover the whole stretch.

Please write to me if you have informations that complement or complete this article. You find my email at the bottom.

Overview

Linux’ boot process consists of multiple parts, that each start the next part

  1. the BIOS boots
  2. the boot loader gets loaded
  3. the kernel starts
  4. init start
  5. the rest of the userspace processes get started
  6. X starts

We now look at each of the points separately.

the BIOS boots

Normally you can not do much about the BIOS displaying its chatter. Some BIOSes support displaying a custom image, however that’s something you’ll need to find out through reading the technical documentation of your mainboard or BIOS.

the boot loader gets loaded

I’ll only cover here GRUB, since it seems to be the dominant boot loader today.

On an average system GRUB takes ony a second or so to load itself and the kernel. Since this is so short a time I am ignoring it and accepting a “black” screen during that second.

This effect can be achieved by setting timeout = 0 in /boot/grub/menu.lst. This will make GRUB skip displaying the boot menu and directly load the default boot entry. If you need to select a different entry then you’ll have to press cursor down in the split second between the BIOS and before GRUB is loaded.

GRUB will still display a line saying that it is loading the kernel (and if your system is configured accordingly also the init filesystem), as described above that line is visible only for a very short time and thus I am ignoring that here:

Uncompressing Linux... Ok, booting the kernel.

However if you want to remove even that, there is a patch from Ubuntu that seems to do that (I have not tested it): quiet.diff

the kernel starts

GRUB loads the kernel and possibly an init filesystem (named initrd or initramfs in Linux speak). It starts the kernel and if configured accordingly on your system, passes the init filesystem on to the kernel.

You can tell the kernel to display an image as soon as it is started. This is usually referred to as “the frambuffer boot logo”. A howto can be found here.

After displaying the boot logo, the linux kernel will usually proceed with verbosely initializing all the hardware. You can suppress all the output by specifying quietin the kernel boot parameters. Just add the word quiet to the kernel boot parameters in /boot/grub/menu.lst. Mine looks like this:

title           Linux 2.6.24.2
month: "2008/03"
year: "2008"
root            (hd0,0)
kernel          /boot/vmlinuz-2.6.24.2 root=/dev/hda1 ro vga=791 quiet splash
savedefault

init start

After the kernel has started it will either mount and continue with the boot procedure inside the init filesystem (initrd or initramfs) or it will start the init process.

Both the init filesystem and the init process will immediately start babbling aloud about what they are doing.

What we need to achieve at this stage is:

  1. if that applies to make sure that whatever is started in the init filesystem is shut up
  2. to shut up init
  3. to shut up all that follows the first started processes

I will not go into siliencing the init filesystem, since I am not using any but instead made a custom built kernel, that has all the minimally required drivers compiled into it and thus am not qualified to comprehensively cover the init filesystem part.

The init process itself will dump one line where it will identify itself:

INIT: version 2.68 booting

I don’t know how to prevent init from writing that. Patching it out from the source should be easy, however there should be a better way.

the rest of the userspace processes get started

After init and/or the init filesystem are started, they will usually proceed with mounting all the required filesystems and dispatching udev which will try to identify all hardware, load the required drivers/kernel modules and allocate the according device node in /dev.

This will produce another 3 or so lines. It should be easy to disable displaying those by patching the respective init scripts, however there should be some universal and standard way to do that, which I do not know of.

After that, but as soon as possible you can start a userspace splash manager. I’m using splashy, there are numerous others though.

X start

At some final point your application or the login manager will start as an X client. I am doing that like this:

/etc/init.d/splashy stop
xinit /usr/bin/my_app

however there are numerous other ways to achieve this. The point is that you need to stop the splash screen manger before your target application or the login manager is started.

One final ugly unsolved problem is the unaesthetic start procedure of the X server, which will typically first display the infamous classic “X” as the background. One can use xsetroot to set the background once X is loaded however between the start of X and the execution of xsetroot you’ll still be looking at “X”’s default background. Again, there should be a way to initialize the background before X switches into graphics mode with a nice background, which I have not found yet.

Contributions to this HOWTO are gladly accepted, thanks, Tomas Pospisek, tpo_deb at sourcepole.ch.

Note that http://sourcepole.com is doing develpment of embedded Linux systems and will gladly provide consulting and implementation to solve any of the above mentioned or further problems.