Kernel and its Types

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Kernel and its Types
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Table of Contents

• Kernel
• Web Hosting
• Functions of Kernel
• Difference between Operating System and Kernel
• Types of Kernels
• Monolithic Kernel
• Advantages and Disadvantages of Monolithic Kernel
• Micro Kernel

• Advantages and Disadvantages of Micro Kernel
• Hybrid Kernel
• Advantages and Disadvantages of Hybrid Kernel
• Nano Kernel
• Advantages and Disadvantages of Nano Kernel
• Exo Kernel
• Advantages and Disadvantages of Exo Kernel

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Kernel

• It refers to a computer program which acts as a
  servers operating systems central component. It
  functions as a communication manager between the
  resources of a server (memory, processor etc.)
  and the users applications (software). It is an
  Operating Systems most vital component and
  remains active till the time the Operating System
  is not shut down.
• The Operating System controls the entire device.
  This results in the Kernel having full control
  over all that exists in the system/device. As
  soon as a system starts, the Kernel is the very
  first computer program that is loaded into
  memory, post the bootloader. This happens because
  the Kernel is responsible for fulfilling
  activities that involve the management of memory,
  disk, task etc. It makes the choice between the
  processes that the processor needs to execute and
  those that the main memory needs to retain to
  execute.
• It functions as an interface between the user
  applications and the systems hardware
  components. A System Call refers to the request
  made by any process to the Kernel, when the
  Kernel links applications to data processing that
  happens in the hardware.

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Web
Hosting

• Any reference to servers makes it worth
  mentioning the web servers of web hosting
  companies. Web hosting companies lease server
  space to store and make available the files of
  any website to ensure its accessibility over the
  Internet. These companies, also referred to as
  web hosts, provide all the services and
  technology that are required for web hosting.
• These web hosting companies can be referred to as
  the Best Windows Hosting Company or as the Top
  Cloud Hosting Company or even as Website
  Hosting Companies in India.

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Functions of
Kernel

• Ensuring communication between hardware and user
  level application
• Controlling task management
• Controlling memory management
• Controlling disk management
• Deciding incoming processes state

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Difference between Operating
System and Kernel
Operating System- It refers to a system software
that acts as an interface between user and
hardware. Every system needs an Operating System
to function and it is the first program to load
after any system boots. Its types are single and
multiuser Operating Systems, Realtime Operating
System, distributed Operating System,
multiprocessor Operating System. Kernel- It
refers to that system software which is an
Operating Systems part and functions as an
interface between the hardware and applications.
Every Operating System requires Kernel in order
to work. As soon as the Operating System loads,
it is the very initial program that loads.
Monolithic and Micro Kernel are the two types of
Kernels that exist.
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Types of Kernels
There are 5 main types of Kernels which are
mentioned here, in no particular order.
Monolithic Kernels, Micro Kernel, Hybrid Kernel,
Nano Kernel and Exo Kernel. The examples of
Monolithic Kernels are Linux, Unix, XTS-400, Open
VMS etc. Micro Kernels examples are L4, Mach,
AmigaOS, K42, Minix etc. Windows NT, BeOS,
Netware etc. are the examples of Hybrid Kernel.
EROS is an example of Nano Kernel. The examples
of Exo Kernel are Nemesis, ExOS etc. All of these
types of Kernels are described in more detail in
the following slides.
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Monolithic Kernel
In this type of Kernel all the services that are
related to the Operating System operate in the
Kernel space. This means that the implementation
of the user services and the kernel services
happen in the same memory space. This results in
an increase in the size of the Kernel and in turn
leads to an increase in the Operating Systems
size. It also ensures faster execution of process
owing to not having separate user space and
Kernel space.
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Advantages and Disadvantages of Monolithic
Kernel
Advantages- Its performance is good. It ensures
fast execution of process. Disadvantages-
Millions of dependencies exist in it, between the
lines of code and the system components. In the
event that any service fails, system failure
becomes unavoidable. The entire Operating System
has to be modified when there is any addition of
new services.
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Micro Kernel
In this types of a Kernel, different spaces are
used to implement the user services and the
Kernel services. The size of this type of Kernel
decreases because the user space and the Kernel
space are separate in it. This results in
reducing the Operating Systems size as well. It
offers more stability. There are less services in
Kernel space.
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Advantages and
Disadvantages of Micro Kernel
Advantages- It offers more stability. Addition of
new services is easy in it. Disadvantages- There
are too many context switches and system calls in
it.
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Hybrid Kernel
It refers to a Kernel that combines a Monolithic
and a Micro Kernel to ensure that the speed
provided by a Monolithic Kernel is available
along with the stability and modularity that is
offered by a Micro Kernel.
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Advantages and
Disadvantages of Hybrid Kernel
Advantage- It ensures the availability of speed
(Monolithic Kernel) along with modularity and
stability (Micro Kernel). Disadvantage- It
retains the similarities of a Monolithic Kernel
despite being a combination type of Kernel.
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Nano Kernel
In this type of a Kernel, the entire code of the
Kernel is very small. A nanosecond clock
resolution is supported by this type of a Kernel.
Hardware abstraction is offered in it, sans
system services. Since Micro Kernels do not offer
system services either, Nano kernels have become
analogous to Micro Kernels.
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Advantages and
Disadvantages of Nano Kernel
Advantage- It provides abstractions related to
hardware, sans system services. Disadvantage-
There is less usage of it, as it is similar to a
Micro Kernel.
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Exo Kernel
In this type of a Kernel, the management and
resource protection are separate from each other.
This ensures customization that is specific to
applications to be performed by the users. An
end-to-end principle is followed by this type of
a Kernel. It has the least amount of hardware
abstractions and Physical resources are allocated
to applications by it.
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Advantages and
Disadvantages of Exo Kernel
Advantage- It has the least amount of hardware
abstractions. Disadvantage- It has a very complex
design.
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