Convert gpt to mbr with linux

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Converting GPT to MBR?

Post by ninyoras » Mon May 03, 2021 12:29 pm

I wanted to convert my encrypted Linuxmint 19 from GPT to MBR and therefore I did a search and found this: https://www.explorelinux.com/convert-a- . mbr-linux/ and this: https://superuser.com/questions/1011942 . gpt-to-mbr

, then r, g, and w as commands.

After this the output became like this:

user@host:~$ sudo gdisk /dev/sdb GPT fdisk (gdisk) version 1.0.3 Partition table scan: MBR: MBR only BSD: not present APM: not present GPT: not present *************************************************************** Found invalid GPT and valid MBR; converting MBR to GPT format in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by typing 'q' if you don't want to convert your MBR partitions to GPT format! *************************************************************** Command (? for help): q 

user@host:~$ sudo fdisk -l /dev/sdb Disk /dev/sdb: 119,2 GiB, 128035676160 bytes, 250069680 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0x478f0f9c Eszköz Indítható Start Vége Szektorok Size Id Típus /dev/sdb1 2048 1050623 1048576 512M ef EFI (FAT-12/16/32) /dev/sdb2 1050624 2549759 1499136 732M 83 Linux /dev/sdb3 2549760 250068991 247519232 118G 83 Linux 

My laptop is still in UEFI mode and it still works. I downloaded boot-repair but when I boot from a live USB and use it, it finds nothing to repair about (ofc, as SSD is encrypted).
Did I misunderstood something? I wanted to switch back from UEFI to BIOS mode and use MBR instead of GPT. Was it not the thing I had to do to achieve it?

Last edited by LockBot on Wed Dec 28, 2022 7:16 am, edited 1 time in total.
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AndyMH Level 20
Posts: 12135 Joined: Fri Mar 04, 2016 5:23 pm Location: Wiltshire

Re: Converting GPT to MBR?

Post by AndyMH » Mon May 03, 2021 2:28 pm

What are you hoping to gain by the change?

Booting in UEFI mode off a legacy drive is not a problem — all it does is use up one of your primary partitions. Your drive is only 120GB so a long way from the legacy limit of 2TB.

Encrypting your drive just complicates things — are you sure it is encrypted? I would have expected /dev/mapper to appear in your fdisk output or did you truncate it?

Thinkcentre M720Q — LM21.1 cinnamon, 4 x T430 — LM20.3 cinnamon, Homebrew desktop i5-8400+GTX1080 Cinnamon 19.0

Re: Converting GPT to MBR?

Post by ninyoras » Wed May 12, 2021 8:24 am

Encrypting your drive just complicates things — are you sure it is encrypted? I would have expected /dev/mapper to appear in your fdisk output or did you truncate it?

Does it cause anything if I see this when checking gdisk?

user@host:~$ sudo gdisk /dev/sdb GPT fdisk (gdisk) version 1.0.3 Partition table scan: MBR: MBR only BSD: not present APM: not present GPT: not present *************************************************************** Found invalid GPT and valid MBR; converting MBR to GPT format in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by typing 'q' if you don't want to convert your MBR partitions to GPT format! *************************************************************** Command (? for help): ^C 

user@host:~$ sudo gdisk /dev/sdb GPT fdisk (gdisk) version 1.0.3 Partition table scan: MBR: protective BSD: not present APM: not present GPT: present Found valid GPT with protective MBR; using GPT. Command (? for help): ^C 

AndyMH Level 20
Posts: 12135 Joined: Fri Mar 04, 2016 5:23 pm Location: Wiltshire

Re: Converting GPT to MBR?

Post by AndyMH » Wed May 12, 2021 10:28 am

No. gdisk is for GPT partition tables. I use sfdisk — handles both.

If you are new to linux I strongly suggest you don’t use full disk encryption. If you bork the system it is either impossible or very difficult to get it back. If you have stuff you consider sensitive I recommend veracrypt containers.

Thinkcentre M720Q — LM21.1 cinnamon, 4 x T430 — LM20.3 cinnamon, Homebrew desktop i5-8400+GTX1080 Cinnamon 19.0

karlchen Level 22
Posts: 17363 Joined: Sat Dec 31, 2011 7:21 am Location: Germany

Re: Converting GPT to MBR?

Post by karlchen » Wed May 12, 2021 11:34 am

Answer :
Definitely not possible.

GPT means grand partition table. — So it is a particular partition table. — GPT partitions can only exist on (U)EFI boot systems.
MBR mean master boot record. — So it is not a partition table, but the boot record on a harddisk.
You cannot convert a partition table, GPT or traditional PT, into an MBR.

Harddisks, which have got an MBR, can only have normal partition tables. The system has to use Bios boot or be (U)EFI capable, but running in Legacy Boot mode (=Bios boot).
Limitation: max. of 4 primary disk partitions. You can work around this limitation by creating
+ 3 primary partitions
+ 1 extended partition: inside this extended partition, you can create logical partitions, quite a few of them.

Harddisks, which use GPTs, can have more than 4 primary partitions. Such harddisks can be used only in combination with (U)EFI boot.

—
In case my explanation should be partially unprecise or incorrect, I am sure that someone will chime in and correct me.

The answer to the question, asked in the title, however, will remain the same: A GPT cannot be converted into an MBR.

The people of Alderaan have been bravely fighting back the clone warriors sent out by the unscrupulous Sith Lord Palpatine for 500 days now.
The Prophet’s Song

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How To Convert A Disk From GPT To MBR On Linux?

The firmware interface is a way by which firmware interacts with the operating system. The BIOS is the usual firmware interface while UEFI is the newer one that has some additional features.

MBR uses the standard BIOS partition table while GPT uses Unified Extensible Firmware Interface (UEFI). Using a GPT disk has various advantages over MBR disk, for instance, you can create more than four primary partitions on a GPT disk. Also, the GPT disk is required if the size of a disk is greater than 2 TB.

But in the older systems that come with BIOS only, you can not boot using GPT disk directly instead first you need to convert the GPT disk into MBR only then you can use it.

Ahead in this article, steps are given to convert a disk from GPT to MBR on Linux.

Steps to convert a disk from GPT to MBR

For converting a disk from GPT to MBR we will use gdisk tool. If it is not in your system then first you need to install it. Use the following command to install gdisk in your system-

And then follow the steps given below-

Note: Before converting a disk from GPT to MBR backup any data on it.

Step 1: List and identify the disk

Use the command that is given below to list the disk available in your system –

Scroll and identify the disk that is to be converted from GPT to MBR in the output of this command.

Step 2: Run the gdisk tool

Now run the following command in the terminal –

Where sda1 is the disk to convert from GPT to MBR. You can see the result of the partition table scan on this disk GPT is present on it.

This will ask you to enter the name of the disk, enter the disk name and then press the return key. It also displays the partitioning scheme available on the disk.

Note:- Here /dev/sda1 is not a partition it is a separate disk, replace /dev/sda1 with the correct drive name on your system for example it could be /dev/sda on your system.

Step 3: Use the recovery and transformation options

Now enter r and then press the return key. Enter the g to convert the disk from GPT to MBR. Next, use the w to write the partition table.

Press the y if asked to accept.

Now the conversion is successful you can verify this by running the following command in the terminal –

As you can see the partition table on this disk is MBR only.

Conclusion

By following this you successfully converted the GPT disk into MBR. Now if you have a query on this then write us in the comments section.

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4 comments on «How To Convert A Disk From GPT To MBR On Linux?»

This saved me SOOOOO much time. Thank you so much for this. I had a terabyte of data on a drive that was GPT formatted in linux to NTFS that then would not read in Windows. Converting it to MBR let it now work in both without spending hours copying then re-copying back.

This is wrong and actively harmful. You need to gdisk /dev/sda, not sda1 – in other words, you need to give it the block device for the entire disk, not a single partition.

Thanks reinderien for pointing this out.
Actually, I demonstrated this guide on a virtual machine with a USB drive which is listed as sda1 on it. I did not know that it could confuse many readers. By the way I added a separate note for this.

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Convert GPT to MBR layout in any Linux Drives

Here we can see how to change from GPT to MBR (Microsoft Master Boot Record), I need to format my pen drive while Installing Linux Mint Using USB, So I have formatted it using gdisk command, After that while I’m trying to format my pen drive using Fdisk it won’t get format, It gives’s the Below Error

Here we can see how to get fix the Error by Converting the GPT to MBR type.

If you using RPM based Machine’s, We can Install gdisk using below command

If you using deb based Machine’s, We can Install gdisk using below command

Then we have to Convert the GPT to MBR

We will get the Below Command Option

GPT fdisk (gdisk) version 0.8.8 Partition table scan: MBR: MBR only BSD: not present APM: not present GPT: not present *************************************************************** Found invalid GPT and valid MBR; converting MBR to GPT format in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by typing 'q' if you don't want to convert your MBR partitions to GPT format! *************************************************************** Warning! Secondary partition table overlaps the last partition by 33 blocks! You will need to delete this partition or resize it in another utility. Command (? for help):

• Recovery/transformation command (? for help):
• Then Convert by giving the command g to convert GPT to MBR
• If you need to see the Preview use P
• Then Write the Changes and Exit the gdisk using w
• Now we can Format the Pen Drive, as usual, using Disk Utility

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