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what is kernel in Linux?

An operating system is a software platform that develops a setting where a user can utilize a computing device to execute various apps. The operating system serves as a link between a system's software applications and hardware parts.

Linux Tutorial Jan 12, 23 by Nisal N 11 min Read
what is kernel in Linux?

The market offers various operating systems used by various gadgets, including mobile phones, tablets, desktop computers, web servers, game consoles, etc.

One of the dependable operating systems that can manage complicated applications and be used to build complex architectures is Linux. 

What does Kernel do?

Since it governs all other programs in a system, the kernel is known as the "heart" of any operating system. 

The initialization function is a process that the kernel does when a device starts, including memory checks. It handles the memory allocation process and establishes a setting that allows apps to execute smoothly.

The kernel serves as a service provider, allowing applications to ask it to perform several jobs. 

For example, a program may ask the kernel to use a disk, network card, or other hardware. The kernel may also set an interrupt for the CPU to support multitasking.

Additionally, it safeguards the computational environment by preventing flawed programs from interfering with other programs' operational processes. 

It prevents the entry of illegitimate programs by denying them memory space and restricting the amount of CPU time they can use.

Types of kernels

In general, there are three types of kernels which are explained below. 

Monolithic kernel

It is a kernel that many operating systems use. The kernel in a monolithic architecture comprises several modules that can be dynamically loaded and unloaded. 

The OS's capabilities would be increased by using an architecture like this, making adding kernel extensions simple.

The monolithic design makes kernel maintenance simple by enabling a concerned module to load and unload when a specific module needs to be fixed for a bug.

Therefore, it avoids the time-consuming process of tearing down and rebuilding the entire kernel for minor changes. 

The monolithic kernel makes it simpler to uninstall a no longer-used module.

MicroKernel

As a replacement for the monolithic kernel, the microkernel has developed to address the problem of the constantly expanding size of kernel code, which the monolithic kernel failed to do. 

Thanks to this architecture, some fundamental functions, including the protocol stack, device driver monitoring, file system, etc., can execute in user space. 

This could increase OS functionality using the least amount of code, improve security, and guarantee stability.

They are allowing the rest of the system to continue generally operating without disruptions limiting the damages to the damaged parts. 

All fundamental OS services are accessible to applications via inter-process communication in the microkernel architecture (IPC). Direct communication between hardware and device drivers is made possible by the microkernel.

Hybrid kernel

The hybrid kernel can choose what applications it wishes to execute in supervisor and user modes. 

Device drivers and file system I/O often operate in user mode in the hybrid kernel environment, while server calls and IPC are preserved in supervisor mode. It provides the best of both worlds.

The Linux Kernel

The foundational element of any Linux-based operating system is the kernel. It stands for the fundamental component of Linux desktop and server distributions. 

It features a monolithic design, and the operating system runs exclusively in the kernel space.

In addition to enclosing the CPU, IPC, and memory, the monolithic kernel controls file system management, device drivers, and system server calls. 

Linus Torvalds developed the Linux kernel in 1991 as a free operating system kernel for his personal computer. Since then, it has grown to support a variety of computer architectures, from smartphones to mainframes. 

Additionally, it serves as the foundation for other free software initiatives like the GNU Operating System. 

Lots of open-source developers from all around the world work on developing the Linux kernel. The Linux kernel is one of the world's largest open-source software projects, with over 23 million lines of code. 

Up to six years of kernel support are provided for each release. The GNU General Public License version 2 governs the distribution of the Linux kernel (GPLv2).

Position of the kernel within the OS

You can think of a Linux computer as having three layers to understand the kernel better:

The hardware

The physical machine, also known as the system's foundation or basis, is composed of input/output (I/O) components such as storage, networking, and graphics, as well as memory (RAM) and the processor, often known as the central processing unit (CPU). 

The CPU runs calculations, reads from memory, and writes to it.

The Linux kernel

the OS's heart. The software running in memory is what directs the CPU.

User processes

These are the active applications that the kernel controls. User space is made up of user processes as a whole. “Just processes” is another name for user processes. 

Additionally, thanks to the kernel, these servers and processes can communicate with one another.

The system's code is executed on CPUs either in kernel mode or user mode. User mode limits access to the CPU and memory to the SCI, but kernel code has unfettered access to the hardware. 

The same division applies to memory (kernel space and user space). Some complex activities, like privilege separation for security, creating containers, and creating virtual machines, are built on these two little aspects.

Subsystems of Linux Kernel

The Linux kernel's primary core subsystems are listed below.

The process scheduler

This is the kernel's main subsystem because it allocates CPU time and resources to each process or program within a fairway. 

No running process will run out of CPU resources, and it will be possible to run multiple apps at once without any of them harming the performance of the others.

The memory management unit

An operating system's memory is a crucial component, and the kernel looks after it. Linux controls the hardware and memory resources for virtual and physical mappings.

Memory management encompasses considerably more than just controlling 4KB buffers. Linux also has slab allocators, abstractions that go beyond 4kb buffers.

The 4kb buffer is the foundation for the slab allocator, which then allocates structures internally by keeping track of which pages are full, empty, and partially used.

This enables the plan to expand dynamically and support the system's more pressing requirements.

The virtual file system

The virtual file system (VFS) is a crucial component of the kernel, making it possible to abstract the file system's common interface. 

The VFS establishes a switching layer between the SCI and the file system that the kernel supports (System Call Interface).

In addition to the features mentioned above, Linux supports a wide range of file systems, each of which requires a unique method of data organization before being stored in a physical format. 

For example, a disk can be formatted with the widely used FAT file system, the ext3 file system that comes standard with Linux, or many alternative file systems.

System call interface

A system call is a programming procedure where a program asks the operating system kernel for a service. 

It consists of numerous hardware functions, including connecting to hardware devices and building a communication interface for the Kernel's essential components. A system call creates an effective interface between an OS and a process.

Architecture-dependent code

Even though a large portion of Linux works on its independent architecture, a few factors must be considered for the design's effectiveness and regular operation.

The architectural subdirectories in Linux each have a large number of other subsidiaries. Additionally, these subdirectories concentrate on the particular functions of the kernel, such as memory management, boot, kernel, etc.

Kernel space and Userspace

The kernel space and Userspace portions of the system memory are separated in the Linux operating system. Let's examine each memory location and learn how they both function.

Kernel space

The kernel space is elevated, giving all hardware devices full access and safeguarding memory space. 

Kernel-space is the collective name for this memory space and user space. Core access to the hardware and system services is upheld and offered to the rest of the system as a service in a kernel space environment.

Userspace

Code that executes outside of the operating system kernel context is called Userspace or Userland.

Applications, programs, and libraries that an operating system utilizes to interface with the kernel are referred to as Userspace. 

Malicious functions are solely limited to the user system because of the difficult process of accessing the memory.

Benefits of the Linux kernel

The following are some benefits of using the Linux kernel:

  • It is thought to operate more quickly because the software is not as involved.
  • Since the kernel is a small piece of software, its source and compiled forms are also smaller.
  • It is likely to have fewer defects and a lower likelihood of security-related issues because of its modest size and code.
  • It only utilizes one address space and one process at a time.
  • It assists in managing all system resources among all active Linux system processes.

Conclusion

The kernel is a key component of the operating system that has made it feasible to execute multiple processes concurrently without risking system failure from a lack of resources. 

It aids in the management of each process' operation and facilitates their communication with the underlying hardware. There are two varieties of kernels: monolithic and microkernel.

Many businesses utilise the combined advantages of the two kernels for the system's best efficiency and production.

The Linux kernel controls how the operating system's resources are used, ensuring adequate memory for applications to operate, maximizing the utilization of the processor, and preventing system deadlocks brought on by conflicting application requests. 

The Linux kernel is a crucial component of many cloud computing infrastructures due to its stability. 

Most cloud solution providers, such as Amazon Web Services and Google Cloud Platform, use Linux and open-source products.

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Nisal N

Computers has always fascinated me since I was a kid and here we are. I love travelling for 2 reasons: the first one to see a new part of the world and second (the most important one) to experience the rich culture hidden among the country and people. I'm pretty good at cooking but very poor when it comes to baking.

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