13.3, Linux kernel Introduction

1. CentOS system Start-up process:

Post (Detect hardware environment)--->bootloader (based on the settings in the BIOS to find out which device to boot from, and then boot the system based on the MBR on the selected device, booting the first stage of grub)---> Load kernel (run kernel image placed in INITRD)--->roofs (Mount root filesystem as read-only)--->switchroot (root switch to official root filesystem)--->/sbin/ Init (first program in user space)

2, Kernel design system: Single core design, micro-core design Two

Linux is a single-core design, but it draws on the design benefits of micro-kernel systems (introducing a modular mechanism for the kernel)

3. Components of the Linux kernel:

There are three main parts: Vmlinuz (core of kernel), kernel object (Kernel objects), RAMDisk (auxiliary file)

3.1 , Vmlinuz: core of the kernel     vmlinuz generally bzimage compressed files, usually in the/boot directory, The name is: Vmlinuz-version-release

3.2, kernel Object: Kernel object       kernel object kernel objects are kernel modules, usually placed in// Lib/modules/version-release  //Note: The version number of the kernel module version-release information must match the version number of the kernel core file     []: N, kernel module not compiled     [m] : modules, compile as kernel module, compile kernel module when used, do not compile when not, the advantage is: Although Occupy disk space, but reduce memory space occupy   

3.3, RAMDisk: Auxiliary files, it is not necessary, depending on whether the kernel can directly drive the device Rootfs, if you can not need, otherwise need this file. RAMDisk can load the drive: Target device drivers: Drivers for SCSI devices Logical device drivers: such as the drive of an LVM device File systems: Drivers such as XFS file systems RAMDisk is a lite version of the root file system, which is placed in memory, it is only to be able to find the real root filesystem exists, the real root filesystem is placed on the hard disk, the data is not lost.

Note: When the system boot is complete and the kernel is loaded, the kernel files we see are static, and the kernel files are changed without immediate effect and restart.

4, Kernel information view:

4.1.

13.3, Linux kernel Introduction