Where is GRUB in the MBR?

Where is GRUB in the MBR?

Where is MBR (GRUB) located, it’s inside a partition? No, it’s not located inside a partition. MBR (Master Boot Record) is the first sector of a disk, so it is 512 bytes on a 512 bytes-sectored disk. Just to note, the first sector of a partition is actually called Partition Boot Record or Volume Boot Record.

Is GRUB stored in MBR?

GRUB is not only located in MBR but contains boot code that loads from a bootable partition (which partition it is depends typically from which operating system you have installed grub). Grub is also called a “boot manager”, because it is able to start more than just one operating system.

Where does Grub run in the boot partition?

The MBR contains just the code to execute Grub2 code which resides on your /boot partition. Grub2 then either chainloads into another partition (for booting windows for instance, as it installs its own boot loader), but it can also run code (things like memtest), or access and run a kernel and module image (vmlinuz).

Where does the GRUB bootloader go in the MBR?

The GRUB bootloader code goes into the MBR as usual, but it needs to be able to find and read the GPT in order to boot the OS. This is new functionality in GRUB2 that wasn’t around in “Legacy GRUB”. The MBR only has room for 446 bytes of executable code, which isn’t much.

How to make grub.cfg pointing to all partitions?

The command grub-mkconfig -o /boot/grub/grub.cfg runs os-prober (if it can find it) which scans all partitions and produces a grub.cfg pointing to all the OSes. Therefore if you have several partitions with /boot (or the MS windows equivalents, I do not know them but os-prober knows) the os-prober will find them and create grub.cfg accordingly.

Can a GPT be booted from a MBR?

The usual bootloader embedded in the MBR isn’t smart enough to do that. Some documentation out there suggests that you need EFI hardware to boot GPT disks. It’s simply not true, we just need some way to meet in the middle. The bootloader, GRUB in our case, is a bridge between the BIOS and the OS.