Convert GPT to UEFI or MBR

Question

I have HDD with Arch linux installed, this disk uses GPT. I would like to convert it to UEFI for using with another laptop (ASUS N56VM), which doesn't support booting from GPT at all (which is strange, because my older ASUS K43SJ can boot GPT with no problem at all).

I know that it's possible to use parted to convert GPT to MBR, however it doesn't boot either with MBR (still laptop recognizes the HDD in BIOS)

Can you please describe steps or point me to an article which I could use as a reference?

Solution

Let's start with some definitions.

• UEFI is the successor to the more traditional BIOS. The implementations vary but they all offer a BIOS compatibility mode (may be disabled by default).
• GPT is the successor to the traditional DOS partition table that offers a number of benefits notably support for booting from drives >= 2TB and >4 partitions without using a "hackish" extended partition.
• UEFI/GPT boot standard utilizes a FAT32 "ESP" partition to contain the relevant bootloader files.
• BIOS/DOS boot standard writes the bootloader within the first 512 bytes (MBR) which often chainloads configuration files from a partition.

As you mentioned laptops and the maximum capacity for 2.5" drives is 1TB currently and your priority appears to be maximizing compatibility, a traditional BIOS/DOS/MBR is recommended.

You may utilize gdisk or another tool for the conversion (though loss of data is high for such a task) and then install GRUB bootloader to the MBR. You may need to enable BIOS-compatibility mode in the UEFI settings to boot.

Comments

[user1984103]

You can't convert GPT to UEFI. UEFI is used for booting the system (like BIOS), while MBR and GPT are partition table formats. Moreover, UEFI is required to have support for GPT disks - it's in the specification. If your system boots with UEFI, then it can support a GPT disk.

[Ramhound]

Your system is already supports and has UEFI enabled if your using a GPT partition your system also is not booting into BIOS what you want to do is not possible

[Rod Smith]

As a general rule, it is possible to boot from a GPT disk on a BIOS-based computer; however, some BIOSes do have bugs that make it necessary to jump through some extra hoops. It's unclear what the current state of the disk is (GPT or MBR) and what data it contains. Elaborating on these points is necessary before a more specific answer can be given, although justbrowsing has covered some of the basics.