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Expanding Disk Partitions in Ubuntu VMs

Overview

When you increase the disk size of a virtual machine (e.g., in VMware, Azure, AWS, or other hypervisors), the underlying storage is expanded but the partition table and filesystem don't automatically grow. This guide covers how to expand partitions and filesystems in Ubuntu to use the newly allocated space.

Check Current Disk Usage

First, verify the current disk space and partition layout:

# Check filesystem usage
df -h

# Check block devices and partitions
lsblk

# Check partition details
sudo fdisk -l

You'll typically see that the disk size (e.g., /dev/sda) is larger than the partition size (e.g., /dev/sda1).

This is the simplest method, especially for cloud VMs.

Step 1: Install cloud-guest-utils (if not present)

sudo apt update
sudo apt install cloud-guest-utils

Step 2: Grow the partition

# Syntax: growpart <device> <partition-number>
sudo growpart /dev/sda 1

# For NVMe drives, use:
sudo growpart /dev/nvme0n1 1

Step 3: Resize the filesystem

For ext4 filesystems: 

sudo resize2fs /dev/sda1

# For NVMe:
sudo resize2fs /dev/nvme0n1p1

For xfs filesystems: 

sudo xfs_growfs /

Step 4: Verify the changes

df -h
lsblk

Method 2: Using parted (Alternative)

If growpart is not available, you can use parted:

Step 1: Launch parted

sudo parted /dev/sda

Step 2: Resize the partition

(parted) print free
(parted) resizepart 1 100%
(parted) quit

Step 3: Resize the filesystem

sudo resize2fs /dev/sda1

Method 3: Using fdisk (Manual Method)

Warning: This method requires deleting and recreating the partition. The data is preserved if done correctly, but proceed with caution.

Step 1: Launch fdisk

sudo fdisk /dev/sda

Step 2: Delete and recreate the partition

Command (m for help): p    # Print partition table (note start sector)
Command (m for help): d    # Delete partition
Partition number: 1

Command (m for help): n    # Create new partition
Partition type: p          # Primary
Partition number: 1
First sector: <press Enter to use default - must match old start sector>
Last sector: <press Enter to use all available space>

Command (m for help): p    # Verify the new partition
Command (m for help): w    # Write changes

Step 3: Reboot or inform the kernel

# Option 1: Reboot
sudo reboot

# Option 2: Inform kernel without reboot
sudo partprobe /dev/sda

Step 4: Resize the filesystem

sudo resize2fs /dev/sda1

LVM (Logical Volume Manager) Partitions

If your Ubuntu installation uses LVM (common in server installations):

Step 1: Grow the partition (if needed)

sudo growpart /dev/sda 3  # Typically partition 3 for LVM

Step 2: Resize the physical volume

sudo pvresize /dev/sda3

Step 3: Extend the logical volume

# Check volume group and logical volume names
sudo vgdisplay
sudo lvdisplay

# Extend the logical volume (example names)
sudo lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv

# Or specify a size
sudo lvextend -L +50G /dev/ubuntu-vg/ubuntu-lv

Step 4: Resize the filesystem

# For ext4
sudo resize2fs /dev/ubuntu-vg/ubuntu-lv

# For xfs
sudo xfs_growfs /

Troubleshooting

Partition still shows old size after resize

Reboot the system or run: 

sudo partprobe /dev/sda

"The partition is being used" error with parted

The partition is mounted. You'll need to: 1. Boot from a live USB/CD, or 2. Use growpart or fdisk method which work on mounted partitions

Verify filesystem type

df -T
# or
lsblk -f

Check for errors after resize

sudo e2fsck -f /dev/sda1  # For ext4 (must be unmounted)
sudo xfs_repair /dev/sda1  # For xfs (must be unmounted)

Common Scenarios

Azure VMs

  1. Expand disk in Azure Portal
  2. Wait for the operation to complete
  3. SSH into the VM
  4. Run growpart and resize2fs

VMware VMs

  1. Power off the VM
  2. Expand disk in VMware settings
  3. Power on the VM
  4. Run growpart and resize2fs

AWS EC2 Instances

  1. Modify volume in EC2 Console
  2. Wait for the volume to show "optimizing"
  3. SSH into the instance
  4. Run growpart and resize2fs

Best Practices

  • Always backup before resizing partitions
  • Take a VM snapshot before making changes
  • Verify free space with df -h before and after
  • Check for errors after resizing
  • Plan for downtime if a reboot is required
# Disk and partition information
lsblk -f              # List block devices with filesystem
df -h                 # Disk space usage
sudo fdisk -l         # List all partitions
sudo parted -l        # List partition tables

# LVM commands
sudo pvdisplay        # Physical volumes
sudo vgdisplay        # Volume groups
sudo lvdisplay        # Logical volumes

# Filesystem utilities
sudo resize2fs        # Resize ext2/ext3/ext4
sudo xfs_growfs       # Resize xfs
sudo e2fsck           # Check ext filesystems

References