How to write to both GPT and MBR manually?

boot mbr gpt

7,330

Thank you for your advices.

I followed them and got help from Rod Smith (creater of gdisk).

The problem came from the fact that Easeus (the partition tool I used) was not aware of "hybrid MBR/GPT" systems. It did a mess thus.

Here were the steps to be taken : 1) using gdisk I repaired the GPT : - added the missing Mac partition (command 'n' in gdisk stating the type AF and the begin and end position) - sorted the partitions for it to become the second one as expected (command 's' in gdisk) 2) I have recreated the hybrid MBR based on these data ('x' command and then 'h' command in gdisk).

Of course, Gdisk allows also to create a backup of both partitions tables. That is a great tool and Rod's documentation on his website rodsbooks.com is great too (with examples and so on).

If you have a dual boot Mac with Windows that is great to correct your messed up partitions.

7,330

Stan

Updated on September 18, 2022

Comments

Stan almost 2 years
I have a big deal here. I have a MacBook with three partitions:
1. HFS partition for Mac OS X 10.6
2. NTFS partition for Windows 7 64-Bit
3. NTFS partition for my documents
It thus works with both GPT and MBR. I use rEFIt to switch the system at boot.

Having had troubles with my Windows roaming increasing dramatically (what a pain), I had to increase the size of my second partition after reducing my third partition...

My problem is that my partitioning tool did a mess with the GPT and the MBR (I am a beginner to these systems and I used EaseUS's tool to work on the partitions. It was a big mistake.)

Now I have the following.

In the GPT
```
Partition  Start LBA     End LBA Type

1                 40      409639 EFI System (FAT)     ⇐ The boot sector, I guess
                                                      ⇐ I miss my Mac OS partition (the entry was suppressed by Easeus)
2          126240768   252067839 Basic Data           ⇐ My Windows partition
3          278693928   976773165 Basic Data           ⇐ My Documents partition at the right place
```
In the MBR
```
Partition   Start LBA    End LBA Type

1                   1     409639 EE               ⇐ The boot sector I guess
2              409640  125976615 AF Mac OS X HFS+ ⇐ My Mac OS partition at the right place etc
2           126240768  252067839 07 NTFS/HPFS     ⇐ my Windows partition
3           252069888  976773165 07 NTFS/HPFS     ⇐ my Documents partition at the WRONG old place
```
rEFIt offers me to automatically copy the content of my GPT to my MBR: It would give me back access to my "documents" partition, but I would lose my OS X partition.

How do I manually write in those GPT and MBR to setup both sides? I heard it would be possible with UBCD …
- JdeBP almost 13 years
  
  Neither of those are the boot sector. The EFI System Partition is your system volume and the type EE entry in the old-style partition table is a protective placeholder.
- Stan almost 13 years
  
  OK, thanks for the TIP. But could you tell me how to write those two tables ?
- JdeBP almost 13 years
  
  I was going to, but was beaten by Rod Smith I see. I personally recover from such situations with a hex editor. But my recommendation to you would have been the same as M. Smith's: Re-add the partition to the EFI table using a non-destructive create and then update the old-style table from the EFI one. I also agree with M. Smith on the avoidance of hybrid partitioning unless one knows fully what one is doing. Why don't you just get your 64-bit Windows 7 to use the EFI partition table directly as it can?
Stan almost 13 years

I have burnt the gparted live CD, but when booting on it. It stops with no reason in the middle of the process... No way to have it continue.
harrymc almost 13 years

Does this thread help ? If not, does it stop with any message (or what is the last displayed message) ?
Stan almost 13 years

No actually my problem is not solved... sadly. Rod Smith (the editor of gparted gave me good advices but I can't actually solve my issue... Best regards.
harrymc almost 13 years

The above thread also gave such advice as using a Linux distribution that contains gdisk. The list is here. You might try a LiveCD, for example Fedora LiveCD is one of the best at detecting hardware.