FDisk is the most commonly used command in the hard disk partition, but some readers may not know that the fdisk command has an undisclonic parameter / MBR, if this parameter is not found in the DOS prompt, but this parameter, but this The parameters have a very important role, and MBR is an abbreviation for master boot record. So, how does FDISK / MBR work? Below and readers learn together. Let's take a look at the first sector of the main guiding sector, the hard disk's zero-cylinder zero track, called the main guiding sector, (of course, 512 bytes), the main guiding sector is booted by the main boot record ( MBR), hard disk partition table (DPT, Disk Partition Table) and end flag three parts, the size and offset of each part can be refer to the following table, the main boot record contains a series of parameters and a boot program for the hard disk, boot The program is mainly used to guide the operating system on the partition with activation flags after the system hardware self-test. It performs the last one JMP instruction to skip the boot program of the operating system, so it is often some guided viruses and some multi-system bootstrap's entry point. This section also includes prompt information when starting an error, Invalid Partition Table, Error Loading Operating System, Missing Operating System, and some reserved information. 64 bytes of the hard disk partition table recorded the size, type, which is active partition, etc. (please refer to the relevant information). The last two flag "55AA" of the main guiding sector is the end flag of the main boot sector, and some viruses will modify these two signs, and the report does not find a valid partition table when the system boots. The data of the main guiding sector can be viewed with some tools or write a compiler yourself. When using fdisk / mbr, you will use the first 446 bytes (if you use DD if = / boot / boot.nnnnn of = / / boot / boot.nnnn nnnn in linux) It is 446) After clearing, re-"Install" boot procedures, but does not destroy the hard disk partition table. Installing some security software or new operating systems tend to boot the program will be changed, and some guided sector viruses may occupy this site to achieve the purpose of obtaining the control of the system. In the above case, if the system cannot start the system when operating inadvertently or other reasons, the system can be used to start the system without being used, and then use FDISK / MBR, you should pay attention, you must pay for the disease, let me talk about me. A few examples of experience: 1. One of my classmates used a software called super bodyguard, with the function of the power-on password, but the password was forgotten (made from self-contained), he started from the floppy disk and put the software to delete the software But when it is on time, you still ask him to enter your password. According to what he said, the timing that prompts to enter the password is after the hardware self-test, when I first started, I speculate that the main guiding sector was modified. It is recommended that he use this command after restarting with the Windows 98 boot disk. Remove the start password. 2. Colleague's computer is guided by the virus infection. After the Kingsoft Internet Security detected, he launched anti-virus with Kingsoft Dynasty, but after rebooting, there was this virus, I don't know if he did the floppy disk itself "clean "
