GNU GRUB on MBR-partitioned hard disk drive
image/svg+xml
GNU GRUB on MBR-partitioned hard disk drive
2013-09-21
Shmuel Csaba Otto Traian Xerxes
Shmuel Csaba Otto Traian Xerxes
Wikimedia Commons
GNU GRUB boot.img core.img MBR Master Boot Record
Illustrates the structure of GNU GRUB on MBR partitioned hard disk drives
Each partition table entry comprises of 16 octets:
Master Boot Record
Magic Number
Volume Partition entry #1
Volume Partition entry #2
Volume Partition entry #3
Volume Partition entry #4
Flag
Start CHS
Type
End CHS
Start LBA
Size
4
4 octets
1
1
3
3
Volume Boot Record
Magic Number
boot.img
Empty space
⤵
Master Partition entry #1
Master Partition entry #2
Master Partition entry #3
Master Partition entry #4
Sector #0
Sector #63-232
by Shmuel Csaba Otto Traian; GFDL 1.3 & CC-BY-SA 3.0; 2013-09-20
Empty sectors
core.img32,256 bytes
⤵
Sectors #1-62
Stage 1.5
Contains file system driversso it can address Stage 2by full path and file name
boot.img446 bytes
Stage 1
⤵
Contains an LBA48 pointereitherto Stage 1.5orto Stage 2
/dev/sdxy
/boot/grub
Location varies
Stage 2
Contains file system driversso it can address Stage 2by full path and file name
boot.img can be written toa VBR and chainloadedfrom a different bootloaderpresent in the MBR