Expand Linux VM Disk under Proxmox VE

Step-by-step guide for expanding disk space in Linux VMs

Posted on January 12, 2024

Updated: 12-Dec-2024

Sources:
1 https://pve.proxmox.com/wiki/Resize_disks
2 https://packetpushers.net/blog/ubuntu-extend-your-default-lvm-space/

1. Introduction

Expanding disk space in a Linux VM under Proxmox VE is a common task, especially as storage needs grow over time. This guide walks through the process of safely increasing disk size, updating partitions, and resizing filesystems, with a focus on LVM and ext4 setups.

2. Discovery: Why and When to Expand

You might want to expand your VM disk if:

  • Your root filesystem is running out of space (df -h shows high usage).
  • You need more storage for applications or data.
  • The installer left unused space on your disk or volume group.

Before making changes, check your current disk, partition, and volume group status.

3. Documenting Current State

Check Disk and Partition Layout

fdisk -l
lsblk

Sample output:

NAME                      MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
vda                       252:0    0    67G  0 disk
├─vda1                    252:1    0     1M  0 part
├─vda2                    252:2    0     1G  0 part /boot
└─vda3                    252:3    0    66G  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0    66G  0 lvm  /

Check Filesystem Usage

df -h

Check LVM Volume Group and Logical Volume

vgdisplay
lvdisplay

Look for free space in your VG and current LV size.

4. Completing the Changes

Step 1: Expand the Virtual Disk in Proxmox

Use the GUI or CLI:

qm resize <vmid> <disk> +<size>
# Example: qm resize 100 virtio0 +5G

Step 2: Rescan Disk and Update Partition Table

Inside the VM, rescan the disk:

dmesg | grep vda
# Or for /dev/sda:
echo 1 > /sys/class/block/sda/device/rescan

Use cfdisk or parted to resize the partition:

With EFI (GPT):

parted /dev/vda
(parted) print
(parted) resizepart 3 100%
(parted) quit

Without EFI (MBR):

parted /dev/vda
(parted) resizepart 2 100%
(parted) resizepart 3 100%
(parted) quit

Step 3: Resize LVM Physical Volume

pvresize /dev/vda3

Step 4: Extend Logical Volume

Use all free space:

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

Or add a specific size:

lvresize --size +20G --resizefs /dev/ubuntu-vg/ubuntu-lv

Step 5: Resize the Filesystem

For ext4:

resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv

5. Documenting the Final State

Re-run the following to confirm changes:

df -h
lvdisplay
vgdisplay
fdisk -l
lsblk

Your root filesystem should now reflect the expanded space.

Useful Commands Reference

growpart /dev/sda 3
pvresize /dev/sda3
lvextend -l +100%FREE /dev/pve/root
resize2fs /dev/mapper/pve-root

Notes

  • Always back up important data before resizing disks or partitions.
  • Shrinking disks is risky and not supported by the PVE API; use SystemRescueCD if needed.
  • For more details, see the Proxmox Wiki.

*This workflow ensures you safely expand your VM disk, update partitions, and grow your filesystem, with checks before and after each

Tags: linux