Convert MBR to GPT and Resize Linux Partitions Without Data Loss

1. Check current partition status

Run fdisk -lu to list disks and verify the partition table type. Example output shows /dev/vda with a dos label (MBR) and /dev/vdb also using dos .

2. Convert MBR to GPT

Because the disk is mounted and contains data, first unmount it: umount /dev/vdb1 Delete the existing partition with fdisk /dev/vdb and the d command, then write changes with w. After the partition table is altered, call ioctl() to re‑read it.

Now create a GPT label using GNU Parted:

parted /dev/vdb

mklabel gpt

Confirm the warning about data loss, answer y, then create a primary partition covering the whole disk:

mkpart primary 1 100%

align-check optimal 1

Verify with print that the partition table is now gpt .

3. Create filesystem and mount

Format the new partition: mkfs.ext4 /dev/vdb1 Mount it to /mnt and list contents to confirm the lost+found directory:

mount /dev/vdb1 /mnt

ls /mnt

4. Expand the cloud disk

After the cloud provider has enlarged the underlying block device, verify the new size with fdisk -lu. The disk now shows a larger capacity but still has an MBR label.

Repeat the GPT conversion steps: delete the old GPT partition with rm 1, accept the backup‑GPT fix prompts (choose F), then recreate the partition covering the full space as before.

Mount the partition again, then resize the filesystem online: resize2fs /dev/vdb1 The command reports the new block count and confirms the filesystem now spans the entire disk.

5. Verify final layout

Run df -Th to see the updated sizes. The /dev/vdb1 mount point now shows the expanded size (e.g., 59 GB total, 57 GB available) while the original /dev/vda1 remains unchanged.