Proxmox Disk Ops

LVM Disk Shrinking

This page explains how to shrink VM/CT disks which cannot be done in WebUI.

Before making changes, back up your disk with:

vzdump 10197 --dumpdir /mnt/backup --mode stop

Or create a disk image with:

dd if=/dev/pve/vm-10197-disk-0 of=/mnt/backup/vm-10197-disk-0.img bs=1M

Before making changes, stop the virtual machine:

qm stop 10197   # For VM
pct stop 10197  # For CT

This prevents data corruption.

Before shrinking LVM, you must first shrink the filesystem.

📌 Note: If the disk uses XFS, shrinking is NOT possible. You must create a new smaller disk and move your data.

First, check the filesystem for errors:

e2fsck -f /dev/pve/vm-10197-disk-0

Then shrink the filesystem(this might take some time):

resize2fs /dev/pve/vm-10197-disk-0 64G

This resizes the filesystem to 64GB. Adjust the size as needed.

After shrinking the filesystem, reduce the LVM disk size:

lvreduce -L 64G /dev/pve/vm-10197-disk-0

You may see this warning:

WARNING: Reducing active logical volume to 64 GiB.
THIS MAY DESTROY YOUR DATA! Are you sure you want to reduce pve/vm-10197-disk-0? [y/n]:

Type "y" and press Enter.

📌 Important:

If you shrink LVM before shrinking the filesystem, you will lose data!

XFS cannot be shrunk.

Once the process is complete, restart the VM:

qm start 10197
pct start 10197  # For CT

Inside the VM, check if the disk size is correct:

df -h

If it still shows the old size, run this to adjust the filesystem:

resize2fs /dev/pve/vm-10197-disk-0

If XFS is used or shrinking seems risky, the safest way is to create a new small disk and move the data.

Create a new 64GB disk:

qm set 10197 -virtio1 local-lvm:64G
pct set 10197 -mp0 /mnt/new-disk,size=64G  # For CT

Start the VM and format the new disk.

Move the data to the new disk:

rsync -av /mnt/old-disk/ /mnt/new-disk/

Delete the old large disk.