Linux system start-up process

Start-up process: 1) BIOS: Boot active firmware. will be aware of the first boot device. 2) MBR: The primary boot partition block in the first sector of the first bootable device. This includes the boot loader program. 3) boot loader: a software that can read kernel files to run, boot loader;4) kernel file: Starts the operating system function.

CMOS and BIOS:

The basic function is to record important parameters on the motherboard. Includes system time, CPU voltage frequency, the I/O address of each device is not IRQ, etc., because the record of these data will cost electricity. So the battery is on the motherboard. The BIOS is a program written to a flash or EEPROM on the motherboard, he can run at boot time to load the CMOS parameters, and try to call the boot program in the storage device, into the operating system in one step. The BIOS program can also change the data in the CMOS, and each motherboard calls the BIOS Setup program with a different press key. It is common for a desktop computer to use the [Del] key to enter the BIOS settings screen.

Mbr:

The first sector of the entire disk is particularly important. Because he recorded the whole disk of heavy information!

The first sector of the

Disk mainly records two important information. Each is:
main boot record area (Master boot Record, MBR): Where the boot manager can be installed, there is 446 bytes;
Span style= "FONT-FAMILY:SYMBOL; Font-size:10pt ">? cut table (partition table): Record the state of the entire hard disk cut, with a bytes MBR is very important, because when the system on the boot will be active to read the contents of this chunk, so the system will know your path to!

< Span style= "font-size:12pt" >

< Span style= "font-size:12pt" > boot loader:

The main tasks are under these items:
? provide a menu : Users can choose different boot projects, which is also an important function of multi-boot.
? load Core Archives : direct pointing to the bootable program section to start the operating system;
transfer to other loader : Transfer the power-on management function to other Loader is responsible. above the first two points are easy to understand, but the 3rd is very interesting Oh!

That means that your computer system may have more than two start-up management procedures. Is it possible? Our hard drive is not just have an MBR just? That's right. However, the boot management program can be installed in addition to the MBR, but also to install in each cutting slot of the boot sector (boot sector) Oh. Cutting slots and all the other Kai contact areas, huh? Oh, yes! This feature will be able to create a "multi-guide" function Ah! Let's say for example. If your personal computer just has a hard drive, it is cut into four slots, the first of which is the Windows and Linux installed in the cutting slot. How do you choose to boot up with Windows or Linux? If the MBR is installed in the same time to know the Windows/linux operating system to boot management program, then the entire process can be the icon as follows:

In the We can find that the MBR's boot management program provides two menus. Select Single (M1) to load directly into WindowsThe core file is turned on, and menu two (M2) is the boot contact area (boot sector) that gives the power-on management to the second cutting slot. When theWhen the user selects the menu two o'clock, then the whole boot management will be handed over to the second cutting slot of the boot management program. WhenAfter the second boot manager starts, there is only one boot menu in the Boot Manager (middle). So just use Linux.Core file to boot. This is the work of multi-boot. We will make a summary:
?Each cutting slot has its own starter contact area (boot sector)
?The system slots in the figure are the first and second cutting slots.
?The actual boot of the core files are placed in each cutting groove!
?Loader just will know their own system slots within the boot core files, as well as other loader only;
?Loader can directly led to or indirectly transfer the management authority to another management procedure.

Now think about it, why do people often say: "If you want to install multiboot, it's best to install Windows before installing"What about Linux?" This is due to:
?When Linux is installed, you can choose to install the Boot manager in the boot sector of the MBR or individual cutting slots, andlinux loader can manually set the menu (that is, M1, M2 ...), so you can Boot ? windows when installed, his installation program will actively cover the MBR as well as the boot fan of his cutting slot District. You have no choice, and he does not have the ability to choose the menu for us. So let's say you install Linux and then install Windows. The MBR boot management program will only have Windows items install Linux once? Of course, no need. You just have to use all kinds of methods to deal with the contents of the MBR. such as the use of all Chinese spfdisk (http:// Spfdisk.sourceforge.net/linux rescue mode to save the MBR can be.

Linux system start-up process