Centos 6.x Startup Process

Centos 6.x Startup Process

 

/Boot Partition

Boot partitions can be identified by default. Therefore, boot partitions can be identified when the system cannot load hard disks!

 

Initramfs memory File System

In centos 6. x, The initramfs memory file system replaces the initrd RAM disk in centos 5. X. Their functions are similar. They can load the boot loader to the memory and then load the kernel modules required during the Startup Process [used to simulate the real Linux File System structure. The details are as follows]. such as USB, SATA, SCSI hard drive and LVM, raid file system driver.

 

Test the initramfs File System

Mkdir/tmp/initramfs

# Create a test directory

 

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

# Copying an initramfs File

 

CD/tmp/initramfs/

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

# It can be seen that a gzip compressed file

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

The suffix of the modified file is .gz.

 

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

# Decompress

 

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

 

Cpio-ivcdu <initramfs-2.6.32-279.el6.i686.img

# Continue Decompression

Ls

# It can be seen that it is very similar to the real Linux File System!

 

Run the/sbin/INIT process

Call the/etc/init/RCs. conf configuration file

There are two main functions:

First, call/etc/rc. d/rc. sysinit, and then initialize the Linux system by the/etc/rc. d/rc. sysinit configuration file.

Then, call the/etc/inittab. Then, the/etc/inittab configuration file determines the default running level of the system.

[Although the order of writing in the/etc/inittab file in centos 5. X is different from the above, the actual execution order is the same!]

 

Initiated by/etc/rc. d/rc. sysinit

1. Obtain the Network Environment

2. Mount the device

3. Boot screen Plymouth (replace the previous rhgb)

4. Determine whether SELinux is enabled

5. Welcome screen displayed during startup

6. initialize the hardware

7. Loading user-defined modules

8. Configure Kernel Parameters

9. Set the Host Name

10. synchronous Storage

11. device Mapper and related Initialization

12. initialize the software disk array (RAID)

13. initialize the file system function of LVM

14. Check the Disk File System (fsck)

15. Set the disk quota (quota)

16. Remount the System Disk in read/write mode

17. Update quota (optional)

18. Start the system virtual random number generator

19. Configure the machine (not necessary)

20. Clear temporary files during the Boot Process

21. Create an ice directory

22. Start swap partition (SWAP)

23. Write the boot information to the/var/log/dmesg file.

 

Call the/etc/rc. d/RC file

Run-level parameter input/etc/rc. after the script D/RC, the script file starts/etc/rc [0-6] according to different running levels. d/corresponding program in the directory

 

/Etc/rc3.d/K ?? File (?? Is a number), which is closed in order of numbers.

/Etc/rc3.d/s ?? File (?? Yes.

 

/Etc/rc. Local file

As long as the related commands are written to this file, the command will be automatically executed when the system starts!

 

Appendix-two hardware self-inspections:

1. Firmware self-check

2. Linux kernel self-check

Centos 6.x Startup Process