Linux Boot Process

Kernel is the main program in a Linux system. 
It has two components:
1. The Main Kernel file
2. Supplementary Kernel files or Kerner Modules

Kernel Modules provide extra functionality and drivers.

init is the main program that is run when a Linux system starts. This program is responsible for managing other startup processes.

In order to lookup Modules, run this cmd:
lsmod
This command lists all the current modules and what are they used by.

modinfo <module_name>
This command tells you about the actual module - its license, author etc.

insmod <module_filename>
This cmd loads a single module by inserting it into the kernel. Requires full file name.
eg. $ insmod /lib/modules/2.6.0/-/-/-/filename.ko

modprobe <module_name>
This cmd loads the specified module and all the other modules that this one depends on, automatically. Doesn't require full filename - just the module name works fine.
eg. $ modprobe cdrom

modprobe uses /etc/modprobe.conf

modprobe -l lists all availalbe modules

rmmod <module_name>
This cmd removes a loaded module

depmod - rebuilds the modules.dep file when run as root

Bootloaders:

LILO and GRUB

LILO - LInux LOader
GRUB - GRand Unified Bootloader

LILO:
/etc/lilo.conf
Let's you load up to three OS by default - two linux and one non-linux
default  option is the one that loads automatically
you need to reinstall LILO after changing the config file by using the cmd lilo 


GRUB:
/boot/grub/menu.lst or grub.conf


The Boot Process:

1. Power is turned on, CPU gets electrical power
2. CPU runs BIOS
3. BIOS runs BootLoader
4. BootLoader loads the kernel into the memory and executes it
5. Kernel runs the initial program - init (/sbin/init)
6. init loads and executes the startup programs as defined by /etc/inittab

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