Concepts required to use Linux

Some concepts required to use Linux-general Linux technology-Linux technology and application information. For more information, see the following. 1) MBR means that the DATA on the hard disk is composed of five parts: MBR, DBR, FAT, DIR, and DATA. MBR (Main Boot Record) area, that is, the primary Boot Record area, located in the whole hard disk's 0 track 0 cylindrical 1 sector. The Master Boot Record (MBR) is the "lifeblood" of the hard disk. It is in the most critical position on the hard disk and records the size and location of each partition on the hard disk, is an important entry to our data information. If it is damaged, all data on the hard disk will be lost! The primary Boot Record (MBR) of the hard disk and its structure are named as the primary boot sector. The content written by the FDISK program to this sector is called the primary Boot Record (MBR ). This record occupies 512 bytes. It indicates that the system control is handed over to the user-specified operating system zone that is registered in the partition table when the hard disk is started.

MBR does not belong to any operating system, nor can it be read using the disk operation commands provided by the operating system. But we can use the INT13H 2 function provided in the ROM-BIOS to read the content of this sector, it can also be read by the software tool Norton8.0 DISKEDIT. EXE .)

MBR primary boot records MBR primary Boot Program (1) Primary Boot Program (offset h--0088h), which is responsible for loading from the active partition and running the system boot program. (2) · error information data area. The offset address 0089H--00E1H indicates an error message, and 00E2H--01BDH indicates 0 bytes. (3) · a Partition Table (DPT, Disk Partition Table) contains four Partition items, with an offset of 01BEH--01FDH. Each Partition Table item is 16 bytes long, A total of 64 bytes are partition item 1, partition item 2, partition item 3, and partition item 4. (4) The ending flag. The two byte values of the Offset address 01FE--01FF are the ending flag 55AA. If this flag is incorrect, the system cannot start.

In MBR, where the partition information structure occupies 512 bytes, the 64 bytes at the offset of 01BEH--01FDH are four partition items (partition information table ). It is determined by the disk media type and the user's definition of partitions using FDISK. In practice, FDISK can divide a disk into less than four primary partitions, but not more than four. The project of each partition table is 16 bytes.

When the MBR main functions and workflow start PC, the system first tests the hardware device. After the test is successful, the udf int 19 H is started, then read the content of the system disk's 0-cylinder, 0-head, and 1-Sector Master Boot Record (MBR) to the area where the memory specified unit 0: 7C00 address starts, and execute the MBR program segment.

The Master Boot Record (MBR) of the hard disk does not belong to any operating system. It is transferred to the memory before all operating systems and plays a role, then, the control is handed over to the operating system in the primary partition (active partition), and the hard disk is managed using the primary partition information table. The main functions of the MBR segment are as follows: · check whether the hard disk partition table is in good condition. · Search for bootable "active" partitions in the partition table. · Load the content of the first logical sector of the active partition into the memory. In the DOS partition, the content of this sector is called the DOS Boot Record (DBR ).