Analyze the definition and functions of Linux MBR

The definition and role of Linux MBR

In the Linux system, MBR (Master Boot Record) is a very important part, which is located in the first sector of the hard disk and occupies 512 bytes of space. The role of MBR is to provide a boot program when the computer starts to help the system load the operating system.

The structure of MBR

The structure of MBR is as follows:

1. Boot code area (446 bytes): This part contains the boot loader The code responsible for starting the operating system.
2. Partition table (64 bytes): The partition table records the partition information on the hard disk, including the starting position, size, partition type, etc. of each partition.
3. Signature (2 bytes) : The last two bytes are used to store the identifier 0x55AA, indicating that this is a valid MBR.

The role of MBR

When the computer starts, the BIOS will load the MBR of the hard disk into the memory for execution. The boot loader in the MBR reads the partition table, finds the active partition (Active Partition) and loads the boot sector of the partition to start the operating system.

Practical operation demonstration

The following is a simple practical operation to demonstrate how to view and modify the MBR in the Linux system.

View MBR

sudo dd if=/dev/sda of=mbr_backup bs=512 count=1
hexdump -C mbr_backup

Through the above command, we back up the MBR of the hard disk sda to a file and view the contents of the file through the hexdump command. You can see the structure of the MBR and the contents stored in it.

Modify MBR

sudo fdisk /dev/sda
Command (m for help): a
Partition number (1-4): 1
Command (m for help): w

The above command uses the fdisk tool to edit the partition table of the hard disk sda and set the first partition as the active partition. This can modify the active partition recorded in the MBR, thus changing the operating system loaded when the system starts.

Summary

MBR, as the first door for computer startup, is crucial to the system startup process. By understanding the structure and function of MBR, we can better understand the system startup process and make adjustments and repairs when necessary. I hope this article will be helpful to you, and you are welcome to continue to study and explore in depth.

Recommendation: Be careful when operating MBR. Misoperation may cause the system to fail to start or data to be lost. Please be sure to back up important data and operate with caution.

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