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poornaMoksha 29Jan2011 21:06

What is Operating System, Kernel and Types of kernels
 

1. What Is Kernel?



A kernel is a central component of an operating system. It acts as an interface between the user applications and the hardware. The sole aim of the kernel is to manage the communication between the software (user level applications) and the hardware (CPU, disk memory etc). The main tasks of the kernel are :
  • Process management
  • Device management
  • Memory management
  • Interrupt handling
  • I/O communication
  • File system...etc..

2. Is LINUX A Kernel Or An Operating System?



Well, there is a difference between kernel and OS. Kernel as described above is the heart of OS which manages the core features of an OS while if some useful applications and utilities are added over the kernel, then the complete package becomes an OS. So, it can easily be said that an operating system consists of a kernel space and a user space.

So, we can say that Linux is a kernel as it does not include applications like file-system utilities, windowing systems and graphical desktops, system administrator commands, text editors, compilers etc. So, various companies add these kind of applications over linux kernel and provide their operating system like ubuntu, suse, centOS, redHat etc.

3. Types Of Kernels



Kernels may be classified mainly in two categories
  1. Monolithic
  2. Micro Kernel
1 Monolithic Kernels

Earlier in this type of kernel architecture, all the basic system services like process and memory management, interrupt handling etc were packaged into a single module in kernel space. This type of architecture led to some serious drawbacks like 1) Size of kernel, which was huge. 2)Poor maintainability, which means bug fixing or addition of new features resulted in recompilation of the whole kernel which could consume hours

In a modern day approach to monolithic architecture, the kernel consists of different modules which can be dynamically loaded and un-loaded. This modular approach allows easy extension of OS's capabilities. With this approach, maintainability of kernel became very easy as only the concerned module needs to be loaded and unloaded every time there is a change or bug fix in a particular module. So, there is no need to bring down and recompile the whole kernel for a smallest bit of change. Also, stripping of kernel for various platforms (say for embedded devices etc) became very easy as we can easily unload the module that we do not want.

Linux follows the monolithic modular approach

2 Microkernels

This architecture majorly caters to the problem of ever growing size of kernel code which we could not control in the monolithic approach. This architecture allows some basic services like device driver management, protocol stack, file system etc to run in user space. This reduces the kernel code size and also increases the security and stability of OS as we have the bare minimum code running in kernel. So, if suppose a basic service like network service crashes due to buffer overflow, then only the networking service's memory would be corrupted, leaving the rest of the system still functional.

In this architecture, all the basic OS services which are made part of user space are made to run as servers which are used by other programs in the system through inter process communication (IPC). eg: we have servers for device drivers, network protocol stacks, file systems, graphics, etc. Microkernel servers are essentially daemon programs like any others, except that the kernel grants some of them privileges to interact with parts of physical memory that are otherwise off limits to most programs. This allows some servers, particularly device drivers, to interact directly with hardware. These servers are started at the system start-up.

So, what the bare minimum that microKernel architecture recommends in kernel space?
  • Managing memory protection
  • Process scheduling
  • Inter Process communication (IPC)
Apart from the above, all other basic services can be made part of user space and can be run in the form of servers.

QNX follows the Microkernel approach

shabbir 29Jan2011 21:23

Re: What is Operating System, Kernel and Types of kernels
 
I think Linux is an OS because it does includes user space. Unix you can say kernel but I would not agree in the true sense because Unix also had user space though no GUI

poornaMoksha 29Jan2011 21:51

Re: What is Operating System, Kernel and Types of kernels
 
Well, I think Linux is a just a kernel developed by Linus while the distributions like fedora, red-hat etc are OS.

lionaneesh 29Jan2011 23:32

Re: What is Operating System, Kernel and Types of kernels
 
Quote:

Originally Posted by poornaMoksha (Post 78509)
Well, I think Linux is a just a kernel developed by Linus while the distributions like fedora, red-hat etc are OS.

Actually ... I disapprove on this...
Shabbir is right....
Its a OS not a kernel...
Linux is a OS that uses the Linux kernel...
Wikipedia also Provides the same :-

http://en.wikipedia.org/wiki/Linux

And i must say...

Good article...Great start!!!!!

poornaMoksha 30Jan2011 00:21

Re: What is Operating System, Kernel and Types of kernels
 
have a look at ubuntuforums.org/showthread.php?t=1223771

lionaneesh 30Jan2011 08:15

Re: What is Operating System, Kernel and Types of kernels
 
Quote:

Originally Posted by poornaMoksha (Post 78515)
have a look at ubuntuforums.org/showthread.php?t=1223771

Is the link Ok...
I cant open it!!!

poornaMoksha 30Jan2011 09:19

Re: What is Operating System, Kernel and Types of kernels
 
Just copy n paste the link into ur web browser and open it . actually i was not able to post the complete link as i was getting an error like " too many live link or image in your post content"..so i removed the initial string and posted the link.
hope this helps!!!!!

lionaneesh 30Jan2011 09:37

Re: What is Operating System, Kernel and Types of kernels
 
Quote:

Originally Posted by poornaMoksha (Post 78521)
Just copy n paste the link into ur web browser and open it . actually i was not able to post the complete link as i was getting an error like " too many live link or image in your post content"..so i removed the initial string and posted the link.
hope this helps!!!!!

Ofcource i know how to open a link...

But its only loading and at the end of that...
The page is blank....

poornaMoksha 30Jan2011 09:51

Re: What is Operating System, Kernel and Types of kernels
 
Well, I am able to open it that way... not sure what problem you are facing..:mean:

lionaneesh 30Jan2011 09:57

Re: What is Operating System, Kernel and Types of kernels
 
Quote:

Originally Posted by poornaMoksha (Post 78524)
Well, I am able to open it that way... not sure what problem you are facing..:mean:

Yeah!! I am also confused on that....

I'll try to open it some time after...
Maybe there is some problem with My ISP...


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