Master Boot Record (MBR)
Introduction
It is an outdated partition scheme that is introduced many decades ago. It can only handle up to 2TB information due to design constraints
All of the critical information for MBR to work is stored in the first 512-byte sector at the first sector of our storage device
Concepts
Master Boot Code
Located at first 446 bytes in critical information sector
When BIOS finish hardware check, it reads master boot code and transfer control to it
It is responsible for examining partition table, identify active partitions, and then load OS boot loader from OS partition
Partition Table
64 bytes following master boot code sector
The table can only hold four partition entries, where each entry consuming exact 16 bytes. This is the root cause why MBR can only hold four partitions
Every entry contains
- Partition starting address
- Size of the partition
- Partition type
- Status flag indicating whether the partition is bootable
Boot Signature
The last 2 bytes in MBR sector. It serves as validity check whether MBR is ok