Introduction to RHEL6 server system startup

1. First, let's take a look at what the system has done from pressing the power switch to seeing the screen: (1) press the power to start the system --> bios (configure the motherboard program, basicinputandoutputsystem, power-on self-check, find the number of the Startup Device) -- & gt; find mbr (masterbootloaderrecord, which belongs to the hard disk 0 disk 0 sector) --> grub --> Use grub to find vmlinuz and initrd (driver

1. First, let's take a look at what the system has done from pressing the power switch to seeing the screen:
(1) press the power to start the system --> bios (configure the program of the motherboard, basic input and output system, power-on self-check, find the number of the Startup Device) --> Find mbr (master bootloader record, it is a hard disk with 0 disks and 0 sectors) --> grub --> Use grub to find vmlinuz and initrd (driver hardware) --> kernel startup, generate the init process -->/etc/inittab (determine the system startup level) -->/etc/rc. sysinit (obtain the network environment and host type of the host, test and load the device, whether selinux is started, and load the module, set the system time .................) -- Read/etc/fstab --> Start the corresponding service at the startup level in order -->/etc/rc. local ----> logon Interface

(2) boot ---> bios hardware self-check ---> load MRB into the memory, bois completes the task, and transfers all the control to Bootloader (Grub) ----> Read grub. conf configuration file, load the corresponding kernel, initialize the image file to the memory, initialize the image file to load a series of hardware drivers, and start the necessary hardware pioneers, the kernel eventually understands the hardware --> Generate the first process init ---> init reads the configuration file/etc/inittab to get the level at which the system will run ---> init runs rc. sysinit script to initialize the system (configure the host name, generate all the device files under/dev/, read/etc/fstab for partitioning and mounting) ---> init according to the running solution, all service startup scripts under the directory corresponding to the running level --> RUN rc. local ---> init generates multiple terminals/sbin/mingetty according to the configuration file. ---> each terminal runs the login ----> RTL ---> GUI logon program.

The above two are the tasks in the system startup process, which are similar in writing. I personally think the first one is better understanding. Of course, everyone's thoughts and opinions are different, so I wrote both cases.

2. MBR
MBR = 512 byte = 446byte boot device information + 64byte partition table information + 2byte partition bit

3. GRUB System Boot Program
The full name of grub is: Grand uniied Boot Loader. From this literal sense, we can know that it is all necessary to load the system and boot the system.
(1) Let's put it out and see what advanced stuff is:
[Root @ rootbug ~] # Rpm-qa | grep grub
Grubby-7.0.15-3.el6.x86_64
Grub-0.97-77.el6.x86_64
(2) View Details of the software

[Root @ rootbug ~] # Rpm-qi grub-0.97-77.el6.x86_64
Name: grub Relocations: (not relocatable)
Version: 0.97 Vendor: Red Hat, Inc.
Release: 77. el6 Build Date: Thu 01 Mar 2012 12:14:36 AM CST
Install Date: Tue 27 Aug 2013 06:37:52 pm cst Build Host: x86-004.build.bos.RedHat.com
Group: System Environment/Base Source RPM: grub-0.97-77.el6.src.rpm
Size: 2396735 License: GPLv2 +
Signature: RSA/8, Fri 18 May 2012 08:07:02 pm cst, Key ID 199e2f91fd431d51
Packager: Red Hat, Inc.
URL: http://www.gnu.org/software/grub/
Summary: Grand uniied Boot Loader.
Description:
GRUB (Grand uniied Boot Loader) is an experimental boot loader
Capable of booting into most free operating systems-Linux, FreeBSD,
NetBSD, GNU Mach, and others as well as most extends cial operating
Systems.

(3) Check where the configuration file is stored:
[Root @ www ~] # Ll/etc/grub. conf -- a soft link file is found
Lrwxrwxrwx. 1 root 22 Aug 27/etc/grub. conf-> ../boot/grub. conf

(4) open it to see what the content is:
[Root @ rootbug ~] # Vim/boot/grub. conf

For more details, go on to page 1: http://www.linuxidc.com/Linux/2013-09/89814p2.htm