CentOS system Start-up process

CentOS 6 startup process:

POST--Boot Sequence (BIOS)--BootLoader (MBR)--Kernel (RAMDisk)--Rootfs Switchroot /init---/etc/inittab,/etc/init/*.conf--Set the default run level--system initialization script--shut down or start the service under the corresponding level-boot terminal grub (boot Loa Der):

1. Grub:grand Unifiedbootloader

2. Grub 0.x:grub Legacy

3. Grub 1.X:GRUB2 Grub Legacy:

4. Stage1:mbr

5. STAGE1_5:MBR after the sector, so that the stage1 in the bootloader can identify the Stage2 partition on the file system;

6. Stage2: Disk Partitioning (/boot/grub/) Profile:/boot/grub/grub.conf <--/etc/grub.confstage2 and kernels are typically placed on a basic disk partition;

Function:

(1) menu and interactive interface available

E: Edit mode, for editing menus;

C: Command mode, interactive interface;

(2) Loading the user-selected kernel or operating system

Allow parameters to be passed to the kernel

To hide this menu

(3) provides a protection mechanism for the menu

Certification for the Edit menu

To enable the kernel or operating system for authentication how to identify the device:

Linux Kernel:

CentOS Boot process: POST--Bootloader (BIOS, MBR)--Kernel (INITRD)--rootfs---Switch_root

Kernel Design System: Single core, micro core

Linux: Single-core design, but fully learn the advantages of micro-kernel system design, the introduction of the kernel of the modular mechanism;

Components of the kernel:

Kernel: Kernel core, generally bzimage, usually located in the/boot directory, named Vmlinuz-version-release;

Kernel object: Kernel objects, kernel modules, typically placed in/lib/modules/version-release/

components of the kernel:kernel, kernel object, RAMDisk

Kernel:uname

Kernel object:lsmod, Modinfo, Modprobe,insmod, Rmmod, Depmod

Ramdisk:mkinitrd,dracut START Process: POST--Bootsequence (BIOS)--Bootloader (MBR)--Kernel (ramdisk)--Rootfs (switch_root)-/sbin/init (/etc/inittab,/etc/init/*.conf,/usr/lib/systemd/system/)--default RunLevel, System initialization, Shut down and start the service, start the terminal (graphics terminal)

Grub:

1st STAGE:MBR

1_5 the sector after STAGE:MBR

2nd stage:/boot/grub/Encryption: Edit, kernel

(hd#,#)

hd#: Disk number, expressed as a number; numbering starting from 0

#: Partition number, expressed in numbers; Numbering starting from 0 (hd0,0) Grub command-line interface

1. Help: Get assistance list

2. Help KEYWORD: More information

3. Find (hd#,#)/path/to/somefile:

4. Root (hd#,#)

Kernel/path/to/kernel_file: Set the kernel file used in this boot, and add many cmdline parameters which the kernel supports.

Example: Init=/path/to/init, selinux=0

1. Initrd/path/to/initramfs_file: Set the RAMDisk to provide additional files for the selected kernel;

2. Boot: Booting the selected kernel, manually booting the system on the GRUB Command line interface:

3. grub> Root (hd#,#)

4. Grub> Kernel/vmlinuz-version-release Roroot=/dev/device

5. Grub> initrd/initramfs-version-release.img

6. grub> Boot configuration file:/boot/grub/grub.conf

Configuration items:

1. default=#: Sets the default Start menu item, and the entry (title) number starts at 0;

2. timeout=#: Specifies the length of time the menu item waits for an option to be selected;

3. Splashimage= (hd#,#)/path/to/xpm_pic_file: Indicates the menu background picture file path;

4. Hiddenmenu: Hide menu;

5. Password [--MD5] STRING: Menu Editor authentication;

6. Title Title: Define the menu item "title", can appear multiple times;

7. Root (hd#,#): Grub finds the device partition where the Stage2 and kernel files are located; "root" for grub;

8. Kernel/path/to/vmlinuz_file [PARAMETERS]: Boot kernel

9. Initrd/path/to/initramfs_file: Kernel-matched Ramfs file;

10. Password [--MD5] STRING: Authentication when the selected kernel or operating system is started; Grub-md5-crypt command enters single-user mode:

(1) Edit the Grub menu (select the title to edit, then use the e command);

(2) attach after selected kernel

1, S, s or single can be;

(3) In the kernel line, type "b" command; Install Grub:

(1) Grub-install

Grub-install--root-directory=root/dev/disk (2) Grub

grub> Root (hd#,#)

grub> Setup (hd#) Exercise:

1, new hard drive, to provide direct operation of the bash system alone;

2, the destruction of the native grub Stage1, and then in the rescue mode repair;

3. Set up protection function for grub; blog job: Grub Application;

Kernel module and kernel Core version must be strictly matched; []:n

[M]:module

[*]:y, compiled into kernel core kernel: dynamic loading and unloading; RAMDisk: Auxiliary files, not required, depending on whether the kernel can directly drive the device Rootfs;

Target device drivers, such as SCSI device drivers;

Logical device drivers, such as those of LVM devices;

File systems, such as XFS file systems; RAMDisk: is a lite version of the root file system; Kernel Information acquisition:

This article is from the "Perfect World" blog, so be sure to keep this source http://angelababy.blog.51cto.com/6326130/1755127

CentOS system Start-up process