WIPEFS GPT INSTALL
WIPEFS GPT UPDATE

For starters, wipe your MBR with wipefs /dev/sda. If at any point you think you messed up, simply do dd if=backupfile of=/dev/sda and you can start over.A copy of the GPT is also stored after the MBR and before the first partition (in this case the first partition starts at sector 2048), so backing up this space should be enough to undo any damage you may cause to your disks dd if=/dev/sda bs=512 count=2048). The MBR is exactly 512 bytes, so just doing a dd if=/dev/sda bs=512 count=1 of=backupfile should be enough to make a copy of the original MBR.

WIPEFS GPT INSTALL

When doing the conversion, boot from a rescue media (or just from install media), otherwise you will not be able to see if the changes you are doing have any impact on the live system (if a partition is in use, the kernel is not able to reload the partition table).

The short version is, Yes, it is possible.

This (noted in a comment) lists more disperse instructions across answers.

You might need to make some room for the EFI System partition.

Your /dev/sda1 starts at sector 2048 so you are good to go.

I can't miss this point (even if mentioned across the board): make a backup of your data.

WIPEFS GPT UPDATE

grub-install to re-install GRUB's EFI bootloader to update the UEFI boot selector.You may have to navigate to the disk: EFI -> ubuntu -> grubењ†4.efi. Use the one-time boot menu to force boot the disk.Change BIOS boot -> UEFI boot in the BIOS.grub-install -target=x86_64-efi /dev/sda to install the GRUB EFI bootloader.Add /dev/disk/by-partlabel/EFI-system /boot/efi vfat defaults 0 2 (or whatever matches items 11 and 12 above) to /etc/fstab, so it is automatically mounted.mkdir /boot/efi to create a mount point for the ESP.mkfs -t vfat -v /dev/disk/by-partlabel/EFI-system (e.g.) to build the filesystem for the ESP.c to set the label of the new partition to something without white spaces.sudo gdisk /dev/sda and then n to create an 'EFI System' partition (ESP).grub-install /dev/sda to re-install the GRUB boot loader using the new partition scheme.partprobe /dev/sda to reload the partition table.Command (? for help): w to write the partition table.Command (? for help): n to create a new 'BIOS boot' (code ef02) partition.Is it possible to perform the conversion and keep my data?ДЇollow this guide (no need to reproduce it here, since it is a SE site). ( Microsoft - Convert an MBR disk into a GPT disk) GPT is also required for disks larger than two terabytes (TB).' One advantage of GPT disks is that you can have more than four partitions on each disk. GUID Partition Table (GPT) disks use Unified Extensible Firmware Interface (UEFI). 'Master Boot Record (MBR) disks use the standard BIOS partition table. The conversion from MBR to GPT pertains to a disk, not a partition:

Wipefs gpt