linux Kernel

[Mario Vukelic]

On Sat, 2006-10-28 at 22:48 +0530, Cheatah 0#@!^ wrote:
> What is the real concept of a linux kernel?

The kernel is the only program with direct access to the hardware (not
strictly true, but true enough for now). It manages all other
applications that run on your computer. 

If you start your computer, the BIOS looks for the first sector on the
hard disk. In the case of Ubuntu Linux, this sector contains the
bootloader "grub". Grub lets you choose which kernel to run (among other
things) and then loads the chosen kernel. The kernel initializes the
hardware and then runs process 0, typically called "init" which finishes
booting untils the machine is usable.


See:
http://en.wikipedia.org/wiki/Kernel_%28computer_science%29
https://help.ubuntu.com/community/Kernel

>  What all are the constituents if it? Are all the folder which we see in the "/"(root folder) the
> constituents of a kernel, or is it a single file ??

The compiled kernel files are in /boot. The actual compiled kernel (that
is the linux kernel in executable state is
called /boot/vmlinuz-<version>. The file /boot/initrd.img-<version>
contains modules (= device drivers) that are already needed at boot
time. There are other files in /boot that are needed by the
kernel. /boot/grub contains the bootloader configuration

The folders in "/" are a property of the file system that is written on
the harddisk. The filesystem in most cases is accessed by modules that
are part of the kernel.

The kernel source code (which can be compiled to an executable kernel)
is available. The central source is www.kernel.org but be aware that
most distributions do not use the sources from kernel.org directly.
Instead, they change them for their needs. Most distributions have
special methods to download and to compile the kernel. For Ubuntu, see
here: 
https://help.ubuntu.com/community/Kernel/Compile



Since Ubuntu is based on Debian, this is also useful:
http://kernel-handbook.alioth.debian.org/
http://www.debian.org/doc/FAQ/ch-kernel.en.html
http://newbiedoc.sourceforge.net/system/kernel-pkg.html