Steps to Convert MBR to GPT Ubuntu / Debian with Images

Step by Step conversion of MBR partition table to GPT & Install Grub-efi

Steps to convert MBR to GPT partition table with UEFI grub.

OS & Release :

lsb_release

check to see if /sys/firmware/efi exists.

[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS

Check Disk & Partition

fdisk -l

Here  20GB Disk, 18.3GB / partition & 1.5 GB swap , There are no space left on drive.

EFI required approx 200M space with FAT16/32 file system. So we have to reduce old partition

Check & change your bios setting ( legacy to uefi )

Step 1:

Boot your system using live Ubuntu 16.4 .

Create Live Ubuntu 16.4 Bootable pendrive OR  Boot Your system using bootable dvd/cd

Step 2:

After boot check to see if /sys/firmware/efi exists.

[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS

Check disk Partition

gdisk -l /dev/sda

Step 3:

Resize partition - Open gparted

gparted

1. Select Ubuntu installed disk for resize ( my disk is /dev/sda )
2. Right click on partition that you want to resize  ( i resize  /dev/sda1 )

3. Press on “Resize/Move”

EFI partition Required size 200M+ so here shrink 250M from / ( sda1 )  

4. Press “Resize/Move”  button

5. Apply Change by Press “Green ✔ check”  

Now you have 251 MB unallocated space for create EFI partition

Step 4:

Convert partition table from mbr to gpt

    gdisk /dev/sda

Press “r” for Recovery/transformation

Command (? for help): r

Press “f” for load MBR and build fresh GPT from it

Recovery/transformation command (? for help): f

Press “w” for save  partition table

Command (? for help): w

Do you want to proceed? (Y/N): Y

Step 5:

Create new EFI partition

gdisk /dev/sda

New partition type “n” and press enter

Command (? for help): n       

Press Enter for default or type partition number

Partition number (2-128, default 2): 2

Set Partition size like +200M or press enter for default

First sector (34-41516446, default = 38434816) or {+-}size{KMGTP}:

Last sector (38434816-38436863, default = 38436863) or {+-}size{KMGTP}:

Current type is 'Linux filesystem' Change partition Type ( EFI code is “ef00” )

Hex code or GUID (L to show codes, Enter = 8300): ef00

Press “p” for checking partition table

Command (? for help): p

Press “w” for save  partition table

Command (? for help): w

Step 6

Update & format EFI partition with fat file system

partprobe

mkfs.vfat /dev/sda2

Note :  need to the file system be FAT32 for EFI

Step 7

Mount the Ubuntu root filesystem ( my root partition is /dev/sda1 )

mount -t ext4 /dev/sda1 /mnt

Note : Here  boot partition is present on / , if you have different /boot mount it using “X” is your partition number

   

   mount /dev/sdax  /mnt/boot

Create folder :

mkdir /mnt/boot/efi

Mount EFI partition

mount /dev/sda2 /mnt/boot/efi

Mount  /dev /proc /sys partition

for i in /dev /dev/pts /proc /sys ; do mount -B $i /mnt/$i ; done

OR

mount --bind /sys /mnt/sys

mount --bind /proc /mnt/proc

mount --bind /dev /mnt/dev

mount --bind /dev/pts /mnt/dev/pts

Step 8

Update /etc/fstab

Update the fstab entries in /mnt/etc/fstab to reflect the partition changes above. Compare the UUID’s there with the ones listed here:

ls /dev/disk/by-uuid -lh

Here EFI partition UUID is “ 9B29-29A6 ”

Add EFI Partition entry

vi /mnt/etc/fstab

……..

# EFI Partition

UUID=9B29-29A6  /boot/efi       vfat    umask=0077      0       1

Step 9

chroot environment

Internet Access required for install grub-efi, update resolv.conf as per your nameserver.

mv /mnt/etc/{resolv.conf,resolv.conf-old}

vi /mnt/etc/resolv.conf

#

nameserver 8.8.8.8

nameserver 8.8.4.4

Note : - DNS server IP - s are need (instead of the internet is accessible, after boot from live USB) because the resolv.conf was empty.

chroot environment

chroot /mnt

Remove grub-pc

apt-get remove grub-pc

Install grub-efi

apt-get install grub-efi

grub-install /dev/sda

Check presence of the efi file:

file /boot/efi/EFI/ubuntu/grubx64.efi

A Boot entry should be listed here:

efibootmgr

exit

reboot