Host planning and disk partitioning

1: In a Linux system, each device is treated as a file, a common device and its file name in Linux. In Linux this system, almost all of the hardware device files are in the/dev directory
IDE hard drive,/dev/hd[a-d]

Scsi/sata/usb hard drive,/dev/sd[a-p]

2: Computer Conversion Unit

8bit (bit) =1byte (bytes)
1024Byte (bytes) =1kb
1024kb=1mb
1024mb=1gb
1024gb=1tb

3: The first sector of the entire disk is particularly important, where each sector is 512bytes, because he records important information about the entire disk! The first sector of the disk mainly records two important information, namely:
X main boot Record area (Master boot Record, MBR): Where the boot management program can be installed, there is 446 bytes

x split table (partition Table): Record the state of the entire hard disk partition, with a bytes

4: Main segmentation, extended segmentation and logical segmentation characteristics let's make a simple definition:
X primary and extended segmentation can have up to four strokes (hard disk limit)

X extended split can only have one (operating system limit)

The X-logical segmentation is a continuous cut-out slot by the extended segmentation;

After x can be formatted, as the partition slot of data access as the main segmentation and logical segmentation. Extended segmentation cannot be formatted;

The number of X-logical divisions varies by operating system, in Linux systems, the IDE hard disk has a maximum of 59 logical partitions (numbers 5th to 63rd), and SATA hard drives have 11 logical partitions (5th to 15th numbers).

5: Boot process with main boot record area (MBR)

We talked about in the introduction of the calculator, there is no hardware to execute the software is useless, in addition to the electricity people, and in order to the computer hardware system resources reasonable allocation, therefore has the operating system this system software production. Because the operating system controls all of the hardware and provides the core functionality, our computer can recognize the file system on the hard drive, and further read the software files in the hard drive and execute the software to achieve the purpose of the software implementation.
The question is, have you noticed that since the operating system is also software, how does my computer know this operating system software and execute his? Obviously when the computer does not have any software system, how does he want to read the operating system files on the hard disk? Hey! This has to involve the computer boot program! Let's talk about this boot program!
In the calculator introduction We have talked about that cute bios and CMOS two things, CMOS is the memory that records the hardware parameters and embedded in the motherboard, the BIOS is a firmware written to the motherboard (again, the firmware is written to a software program on the hardware). This BIOS is in the boot, the computer system will be actively executed the first program!
Next the BIOS will analyze what storage devices are in the computer, we take the hard drive as an example, the BIOS will be based on the user's settings to obtain a bootable hard disk, and to the hard disk to read the first sector of the MBR location. MBR this only 446 bytes hard disk capacity will be placed in the most basic boot management program, at this time the BIOS becomes complete, and the next is the MBR of the boot management program work.
The purpose of this boot management program is to load the core file, since the boot manager is the operating system is provided at the time of installation, so he will know the hard disk File system format, so you can read the core files, and then the core files work, the boot management program has become a success, Then you know the task of the operating system!
Simply put, the entire boot process to the operating system before the action should be this:
1. BIOS: Boot active firmware, will know the first device to boot, 2. MBR: The first boot device in the first sector of the main starting record block, including the boot management program; 3. Boot Manager (boot loader): a software that can read the core file to execute; 4. Core Archives: Start operating system features ...
From the above instructions we will know that the BIOS and MBR are the hardware itself will support the function, as for boot loader is installed in the operating system on the MBR of a set of software. Since MBR has only 446 bytes, this boot manager is very small and beautiful. The main tasks of this boot loader are the following items:
X provides a menu: the user can choose different boot items, which is also an important function of multi-boot! x Load the Core archives: direct to the bootable program section to start the operating system, X to other loader: transfer the power-on management function to the other loader responsible.
The first two points above are easy to understand, but the 3rd is very interesting! That means you may have more than two boot management programs in your computer system! Is it possible? We don't have a single MBR for our hard drive? That's right! However, the boot manager can be installed in addition to the MBR, and can be installed in the boot sector of each split slot (boot sector) Oh! A blind secret? Split slots and all the boot sectors, huh? Oh, yes! This feature can create "multi-boot" function Ah!
Let's say for example, suppose your PC has only one hard disk, which is cut into four slots, where the first to second slot is installed with Windows and Linux, how do you choose to boot with Windows or Linux on boot? Assuming that the MBR is installed in the Windows/linux operating system can also know the boot management program, then the entire process can be the icon as follows:

Figure 2.4.1, boot management program work execution
In the We can find that the MBR boot management program provides two menu, select Single (M1) can directly load Windows core files to boot, menu two (M2) is the boot management work to the second partition slot (boot sector). When the user selects the menu two o'clock when the boot, then the entire boot management work will give the second slot the boot management program. When the second boot Manager starts, the Boot manager (middle) has only one boot menu, so you can use the Linux core file to boot. This is the work of multi-boot! We will make a summary:
X each split slot has its own boot sector (boot sector) x figure in the system slot for the first and second slots, x actual bootable core files are placed in each partition slot! x loader only knows the bootable core files within the system slots, as well as other loader; x loader can direct or indirectly transfer management to another hypervisor.
Now think about why people often say, "If you want to install multiboot, it's a good idea to install Windows and then install Linux." This is because:
x Linux in the installation, you can choose to install the boot manager in the MBR or separate slots of the boot sector, and the Linux loader can be manually set menu (M1, M2 ...), so you can be in the boot of Linux Loader the option of adding windows to the boot;
X windows when installed, his installer will actively overwrite the MBR as well as the boot sector of his partition slot, you have no choice, and he did not let us choose the function of the menu.
Therefore, if you install Linux and then install Windows, then the MBR boot Manager will only have Windows projects, and there will be no Linux project (because the original MBR in the Linux boot management program will be overwritten). Does it need to reinstall Linux once? Of course not, you just have to use a variety of methods to deal with the contents of the MBR. For example, the use of Spfdisk (http://spfdisk.sourceforge.net/) software to install the Knowledge windows/linux management program, but also can use the Linux rescue mode to save the MBR.

6:Selection of disk partitions in Linux installation mode (very important)

7:linux Installation

CentOS, a version that is known to be fully compatible with Rhel, i386 CentOS 5.x can be installed in x86_64 hardware.

Host planning and disk partitioning