How to Extend or Resize the Disk Size of a Proxmox Ubuntu (Linux) VM

When managing virtual machines (VMs) in Proxmox, you might find yourself running out of disk space. Fortunately, extending or resizing the disk size of an Ubuntu VM is straightforward, thanks to Logical Volume Management (LVM). In this blog post, I'll walk you through the process step-by-step, ensuring you can efficiently utilize all the available disk space.

Prerequisites

• A Proxmox VE host with an Ubuntu VM running on it.

• Basic knowledge of the Linux command line.

• Sufficient space on your Proxmox storage pool to extend the VM's disk.

Step 1: Increase the Disk Size in Proxmox

First, you'll need to increase the disk size for your Ubuntu VM within the Proxmox web interface.

1. Shut down the VM: Before making any changes, ensure the VM is powered off.

2. Edit the VM hardware: In the Proxmox web interface, navigate to the VM, click on "Hardware," and select the disk you want to resize.

3. Resize the disk: Increase the disk size by specifying the additional space you want to allocate (e.g., adding 10GB).

4. Start the VM: Once the disk has been resized, start the VM.

Step 2: Verify the New Disk Size in the VM

After resizing the disk in Proxmox and starting the VM, log into the Ubuntu system.

Use the lsblk command to verify the new disk size:

lsblk

You should see the resized disk, but the additional space will likely be unallocated and not yet available to your file system.

Step 3: Extend the LVM Partition

If you're using LVM (which is common in many Ubuntu setups), you'll need to extend the LVM partition to use the newly added space.

1. Scan for the Volume Group

First, verify that your volume group is detected correctly:

vgscan

If your volume group is inactive, activate it:

vgchange -ay ubuntu-vg

2. Check Free Space in the Volume Group

Next, check how much free space is available in the volume group:

vgdisplay ubuntu-vg

In the output, look for the "Free PE / Size" line to see how much space is available for allocation.

3. Extend the Logical Volume

Now, extend the logical volume to use all the available space:

lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv

This command tells LVM to allocate all free space in the volume group to the logical volume.

Step 4: Resize the Filesystem

After extending the logical volume, the final step is to resize the filesystem to use the newly allocated space.

For ext4 filesystems (which is the default in most Ubuntu setups):

resize2fs /dev/ubuntu-vg/ubuntu-lv

This command resizes the filesystem to fill the logical volume. If the filesystem is mounted (e.g., it's your root filesystem /), resize2fs will perform an online resize.

Step 5: Verify the Changes

Finally, confirm that the filesystem is now using the new space:

df -h

You should see that the size of the root (/) filesystem has increased, reflecting the additional space you've allocated.

Example Scenario

Here’s a summary of the commands used in a real-world scenario:

Check current disk layout:

lsblk

Scan and activate the volume group:

vgscan

vgchange -ay ubuntu-vg

Verify free space in the volume group:

vgdisplay ubuntu-vg

Extend the logical volume:

lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv

Resize the filesystem:

resize2fs /dev/ubuntu-vg/ubuntu-lv

Verify the filesystem size:

df -h

Conclusion

By following these steps, you can easily extend or resize the disk size of an Ubuntu VM running on Proxmox. This guide ensures that your VM can efficiently use all the allocated storage, avoiding any potential issues with disk space in the future.

Whether you're managing a single VM or multiple VMs on your Proxmox setup, knowing how to extend disk space is an essential skill that will help keep your virtual environment running smoothly.