Hello ,

I Try to write howto about livecd .. this part explain the "boot process".

Introduction

As you know , MCNLive is a LiveCD based on Mandriva with the mklivecd scripts. To create .iso file, mklivecd use "mkisofs" ( cdrecord project ) and "isolinux" ( syslinux project ).

* mkisofs is used for premastering iso9660 filesystems which are used on CDROMs.
* isolinux is a boot loader for Linux/i386 that operates off ISO 9660/El Torito CD-ROMs in "no emulation" mode.

Ok , now we have a nice .iso file to burn on CDROM. But what's these files inside and their utilities ? Take a look ..



Boot Process

When booting from a LiveCD's boot process is as follows:

1. the BIOS loads itself into memory and executes. you must set BIOS to boot from CD. (--> loads the MBR from CD)
2. ISOLinux is the bootloader. ISOLinux will load the initrd.gz and the kernel image and transfer control to the kernel.
3. Now, linuxrc is a script (initrd.gz) that the kernel will execute as the first process. It does a number of things.

For Eg. It first loads driver's module, searches cdroms for the compressed filesystem image (livecd.sqfs), mounts it, etc ...
When the linuxrc script finishes, /etc/rc.d/rc.sysinit is run.




4. We are now at next stage of the boot process. livecd.sqfs is mount as "real" filesystem and things start as "normal" mandriva boot process.

Visual representation



this is explained correctly ??

David

MCNLive Boot process [ html ]


[EDIT] Here some useful links

From Wikipedia : LiveCD , BIOS , ISO9660 , El Torito , ISOlinux , MBR , Initrd , SquashFS , UnionFS

Looks nice David. I think it's correct, but i'm sure Kris knows more about this

A small note about the text.

The BIOS is not loaded from the CD. A BIOS is always incorperated in the computer and runs before anything else.

The MBR is the master boot record. It is a small piece of program that tells the computer which part of the CD (or disk, when started from HD) to load next. In this case lilo or grub.

I agree with you but i'm sure everyone knows that ( I think )


When you talking about grub/lilo , it's for disk. right ? because ISOlinux is the bootloader in this case

ps : I still modify first post and add some links to wikipedia ( bios , mbr , initrd , etc .. )

David

Yep.