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Install Grub4dos to GPT under Linux


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#1 xpt

xpt

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Posted 21 July 2019 - 07:08 PM

the thread at http://reboot.pro/to...nd-gpt-support/ is getting extremely long and pending further input, so I'd better to start a new thread to ask this simple question -- 

 

How to install Grub4dos to the MBR of a GPT disk, with grub4dos-0.4.6a-2019-07-16, if my GPT disk is /dev/sdd?

Moreover, if I make one partition as active for my GPT disk, and install Grub4dos to its PBR, will it work as well? Would the steps any different that the previous? 

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic

$ uname -rm
4.15.0-54-generic x86_64

Thanks



#2 Wonko the Sane

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Posted 22 July 2019 - 09:20 AM

How to install Grub4dos to the MBR of a GPT disk

 

You CANNOT.

The last character in the above is a dot, full stop or period.

 

A GPT disk has:

Sector LBA 0 containing the protective MBR

Sector LBA 1 containing the disk GPT
Sectors LBA 2 (usually up to 31) containing the partytion table entries

 

grub4dos grldr.mbr code (which is what is installed to the MBR AND to following sectors) is several sectors long (18 if I remember correctly) and it simply won't fit without overwriting VITAL data of the GPT disk.

 

BUT you can write to the MBR code area a small program that chainloads grldr (grub4dos), fitting in the first 440 bytes :) .

 

There are two such codes AFAIK, Chenall's UMBR and my half-@§§ed one, probably :dubbio: something similar is also in Syslinux, but it's a lot of time I don't check the project.

 

See this (loong) thread:

http://reboot.pro/to...in-bios-to-gpt/

 

the "fun" starts around here:

http://reboot.pro/to...o-gpt/?p=193659

 

AND this one:

http://reboot.pro/to...b-with-bootice/

 

AND this one:

http://reboot.pro/to...able-usb-drive/

 

 

 

Moreover, if I make one partition as active for my GPT disk, and install Grub4dos to its PBR, will it work as well? Would the steps any different that the previous? 

Thanks

 

There is NO such thing as an active partition on GPT disk, maybe you are thinking of a MBR-Hybtid one :ph34r:

https://www.rodsbook...isk/hybrid.html

 

:duff:

Wonko


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