Introduction to embedded Linux Kernel

Introduction to embedded Linux kernel Zhang jianbo

 

Linux was first developed by Linus Torvalds of Finland to provide a free and free UNIX-like operating system on intel X86 architecture. To be precise, Linus Torvalds only completes the Linux kernel ".

That is to say, the Linux kernel =/= the Linux operating system.

The popular RedHat and Ubuntu on PCs are developed and expanded based on Linux kernel developed by Linus Torvalds.

About the Linux version:

Linux is different from Microsoft's Windows. The Linux version mainly consists of the kernel version and the operating system version. Of course, the desktop can also be calculated separately.

	Linux operating system	System Version	Linux Kernel version
1	RedHat	9.0	2.4.20
2	RedHat	As 4.0	2.6.9-5.el
3	Ubuntu	9.0	2.6.31-14
3	Ubuntu	10.0.1	2.6.32-21
3	Ubuntu	11.10	3.0.3
3	Ubuntu	12	3.0.3

From the table above, we can see that different Linux operating systems may adopt different linux kernels.

Linux Kernel website http://www.kernel.org/

Generally, Linux kernel upgrades and updates are faster than Linux operating systems. Therefore, many enthusiasts like to "compile the kernel" and "upgrade the kernel ".

Generally, the Linux kernel version number can be used to determine whether the system is a stable version or a test version. Take version 2.4.0 as an example. 2 indicates the primary version, 4 indicates the minor version, and 0 indicates the minor version. In the version number, the version whose second digit is an even number indicates a stable version that can be used, such as 2.2.5, the version with the second digit of the serial number being an odd number usually includes some new things. It is not necessarily a stable test version, such as 2.3.1. In this way, the stable version comes from the upgrade version of the previous test version, and the development of a stable version is no longer mature.

Linux core development and specifications have been controlled by the Linux community, and the version is unique. The kernel version of the operating system refers to the version number of the system kernel developed by the development team under the Linux leadership. Since the first official version of Linux March 14, 1994 was released in 1.0, a new version or its revision has been published at intervals.

Linux Kernel composition:

Simply put, the Linux kernel is like a human heart ".

The Linux kernel consists of process management, timer, interrupt management, memory management, and module management), Virtual File System Interface (VFS layer), file system, device driver, and inter-process communication) and network management.

Differences between embedded Linux and PC Linux operating system startup:

On a PC, Linux is usually started through LILO or grub.

Because lilo has a 1024-byte cylindrical limit, and after changing the boot information file on the disk, You need to restart the system to synchronize the 446-byte content, because of Lilo's defects, it has been replaced by grub. currently, most Linux systems use grub for boot.

In Embedded Linux, such as arm9-( sc2410, sc6410, etc.), is started through the U-BOOT.

Lilo, grub, or U-boot are responsible for the process of "extracting the kernel", "loading the kernel", and "starting the kernel.

Note: the Linux kernel is usually compressed.

 

Differences between embedded Linux kernel and PC Linux Kernel

The embedded Linux kernel is actually a cropping version of the Linux kernel, which is obtained after cropping, customizing, modifying, and cross-compiling. Therefore, theoretically, anyone can download the latest kernel from the Linux kernel official website for transplantation.

Linux Kernel Customization

Linux Kernel customization is not as complicated as you think. By making reasonable modifications to the Linux kernel based on the actual conditions of "hardware" and "requirements", you can effectively simplify the Linux kernel and remove unnecessary components, in this way, the system starts faster and more memory resources are released.

If you are interested, you can start with Linux kernel customization on your PC.

 

This series of articles is written by ex_net (Zhang jianbo). Please indicate the source for reprinting. Http://blog.csdn.net/ex_net/article/details/7908517author: Zhang jianbo mail: 281451020@qq.com Phone: 13577062679 welcome to contact us!