CentOS 6.2 System Detailed start-up process

CentOS 6.X Start-up process

/boot partition

Boot boot is recognized by default. So the boot partition is recognizable when the system is still unable to load the hard drive!

Initramfs Memory File system

CentOS 6.x uses the Initramfs memory file system to replace the INITRD RAM Disk in CentOS 5.x. They work similarly, can be loaded into memory by booting the bootloader, and then load the kernel modules needed during the boot process [to simulate the real Linux filesystem structure, details as follows], such as USB, SATA, SCSI hard drive and LVM, RAID file system driver.

testing the Initramfs file system

Mkdir/tmp/initramfs

#建立测试目录

cp/boot/initramfs-2.6.32-279.el6.i686.img/tmp/initramfs/

#复制initramfs文件

cd/tmp/initramfs/

File initramfs-2.6.32-279.el6.i686.img

#可以看出是一个gzip压缩文件

MV Initramfs-2.6.32-279.el6.i686.img initramfs-2.6.32-279.el6.i686.img.gz

#修改文件的后缀名为. gz

Gunzip initramfs-2.6.32-279.el6.i686.img.gz

#解压缩

File initramfs-2.6.32-279.el6.i686.img

CPIO-IVCDU < initramfs-2.6.32-279.el6.i686.img

#再继续解压缩

Ls

#可以看出, he is very similar to the Linux real file system!

executing the/sbin/init process

Calling the/etc/init/rcs.conf configuration file

The main functions are two:

The /etc/rc.d/rc.sysinitis called first and then the Linux system is initialized by the/etc/rc.d/rc.sysinit configuration file.

The /etc/inittabis then called, and the/etc/inittab configuration file determines the default runlevel of the system .

[Although the writing order in the/etc/inittab file in CentOS 5.X differs from the above, the true order of execution is the same!]

initialized by/etc/rc.d/rc.sysinit

1. Access to the network environment

2. Mounting equipment

3, Boot screen Plymouth (replace the past RHGB)

4. Determine if SELinux is enabled

5, display in the boot process of the Welcome screen

6. Initializing hardware

7, the user custom module loading

8, configure the parameters of the kernel

9. Set Host Name

10. Synchronous memory

11, device Mapper and related initialization

12. Initialize the software disk array (RAID)

13. Initialize the file system function of LVM

14. Test Disk File System (FSCK)

15. Set disk quotas (quota)

16. Re-mount the system disk in read-write mode

17, update quota (not necessary)

18, start the system virtual random number generator

19. Configure the machine (not necessary)

20. Clear the temporary files during the boot process

21. Create an Ice directory

22. Start the swap partition (swap)

23. Write the boot information to the/VAR/LOG/DMESG file

calling the/etc/rc.d/rc file

After the run-level parameter is passed in to the/ETC/RC.D/RC script, the corresponding program in the/etc/rc[0-6].d/directory is started by this script file at different RunLevel

/etc/rc3.d/k?? The beginning of the file (?? is a number) and is closed in numerical order

/etc/rc3.d/s?? The beginning of the file (?? Numbers), which are sequentially started in numerical order

/etc/rc.local File

As soon as the relevant command is written to the file, the command will be executed automatically when the system starts!

Attached-two hardware self-test:

1. Firmware Self-Test

2.Linux Kernel self-test

CentOS 6.2 System Detailed start-up process