---
slug: reduire-taille-disque-vm-clonezilla
title: Reducing VM Disk Size with Clonezilla
authors: [tellserv]
tags: [proxmox, clonezilla, vm, storage, linstor-drbd]
image: /img/blog/2025-11-30-reduire-disque-vm/clonezilla-logo.svg
---

import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';

<p align="center">
  <img src="/img/blog/2025-11-30-reduire-disque-vm/clonezilla-logo.svg" alt="Clonezilla Logo" width="300" />
</p>

How to migrate a VM to a smaller disk while preserving all data using Clonezilla, to optimize Linstor DRBD storage usage in a Proxmox cluster.

<!--truncate-->

:::danger MANDATORY BACKUP
**Before any manipulation, create a complete backup of your VM** via Proxmox Backup Server or `vzdump`. This operation directly manipulates disks and any error can result in data loss.

📚 A detailed article on Proxmox Backup Server is coming soon.
:::

## Context

My production Ubuntu VM from the [Current Homelab](/docs/homelab-actuel) has a **400 GB** disk on Linstor DRBD storage. This oversized disk comes from a time when this OS ran directly on bare-metal before virtualization.

### Problem

After reducing the system partition to **130 GB** (leaving 270 GB of unallocated free space), I want to:
1. Create a new **135 GB** disk (130 GB of data + 5 GB margin)
2. Migrate the OS and data to this smaller disk
3. Free up **265 GB** on Linstor DRBD storage

### Final Goal

Reorganize Proxmox hosts storage:
- **300 GB**: Linstor DRBD (highly available replicated storage)
- **200 GB**: local-lvm (non-replicated local storage)

## Prerequisites

### Required Tools

- **Proxmox VE**: Virtualization hypervisor
- **Clonezilla Live ISO**: Disk cloning tool ([download](https://clonezilla.org/downloads.php))
- **Linstor DRBD**: Distributed storage (see [article on Proxmox distributed storage](/blog/stockage-distribue-proxmox-ha))

### Initial VM State

Before starting, check the current state:

```bash
sudo fdisk -l /dev/sda
```

**Expected output**:
- Disk `/dev/sda`: **400 GiB**
- System partition (`/dev/sda3`): **~120 GiB** used
- Free space: **~270 GiB** unallocated

:::tip Shrink partition beforehand
If you haven't shrunk your partition yet, use `gparted` or `resize2fs` to reduce the filesystem **before** starting this procedure. Leave about 5 GB margin compared to used space.
:::

## Step 1: Create the New Disk in Proxmox

In the Proxmox web interface, access your VM configuration:

1. Select your VM
2. **Hardware** tab
3. Click **Add** → **Hard Disk**

**New disk configuration**:
- **Storage**: `linstor_storage` (or your Linstor DRBD pool)
- **Disk size**: `135 GiB`
- **Bus/Device**: `SCSI` (scsi1)

![VM hardware configuration with both disks](/img/blog/2025-11-30-reduire-disque-vm/vm-hardware-config.png)

:::info
The new disk will appear as `/dev/sdb` in the VM. The original disk `/dev/sda` remains in place for now.
:::

## Step 2: Mount the Clonezilla ISO

Still in the Proxmox interface:

1. Select the **Hardware** tab
2. Double-click **CD/DVD Drive**
3. **Storage**: `local` (or your ISO storage)
4. **ISO image**: Select `clonezilla-live-3.3.0-33-amd64.iso`

**Configure boot order**:
1. **Options** tab → **Boot Order**
2. Enable **CD-ROM** and place it in **first position**
3. Click **OK**

Start the VM via **Console** → **Start**.

## Step 3: Start Clonezilla in KVM To RAM Mode

:::warning Snow problem without KVM To RAM
If you **don't** choose the **KVM To RAM** option, Clonezilla display will show snow (graphical artifacts) making the interface unusable.

![Snow on screen without KVM To RAM](/img/blog/2025-11-30-reduire-disque-vm/neige.webp)
:::

### Boot Mode Selection

At Clonezilla boot:

1. **First option**: Select **Clonezilla live (KVM To RAM, VGA 1024x768)**
2. Press **Enter**

### Clonezilla Initial Configuration

Follow the configuration wizard:

<Tabs>
<TabItem value="language" label="Language">

```
Choose language: [en_US.UTF-8] English
```

</TabItem>
<TabItem value="keymap" label="Keyboard">

```
Configuring console-data: [Don't touch keymap]
```

(or choose your keyboard layout)

</TabItem>
<TabItem value="mode" label="Clonezilla Mode">

```
Start Clonezilla: [device-device]
```

Select **device-device** (disk to disk clone)

</TabItem>
</Tabs>

## Step 4: Clone Disk with Expert Options

### Expert Mode Selection

```
Mode: [Expert mode]
```

Choose **Expert mode** to access necessary advanced options.

### Operation Type Choice

```
Expert Mode: [disk_to_local_disk]
```

Select **disk_to_local_disk** (clone local disk to local disk).

### Disk Selection

1. **Source disk**: `/dev/sda` (400 GiB - old disk)
2. **Destination disk**: `/dev/sdb` (135 GiB - new disk)

:::danger Verify disks carefully
**Warning**: Selecting the wrong disk will permanently erase your data! Check disk sizes before validating.
:::

### Critical Advanced Options

Clonezilla offers several advanced options. **You MUST select**:

#### Option 1: `-k0` (Create partition table proportionally)

```
-k, --create-partition-table
[×] -k0 Create partition table in target disk proportionally
```

**Explanation**: This option recreates the partition table while keeping **original sizes** of partitions (not resizing them proportionally to the new disk).

#### Option 2: `-icds` (Skip checking destination disk size)

```
-icds, --skip-check-dest-size
[×] -icds Skip checking destination disk size before creating partition table
```

**Explanation**: By default, Clonezilla refuses to clone to a disk **smaller** than the source disk. This option disables this check.

:::tip Why does it work?
Even though the destination disk (135 GB) is smaller than the source disk (400 GB), the **used partitions** are only 130 GB. Clonezilla clones only the partitions, not the unallocated empty space.

The `-k0` option ensures partitions keep their original size (130 GB) instead of being resized proportionally to the new disk.
:::

### Start Cloning

1. Validate all options
2. Clonezilla displays a **summary** of parameters
3. Confirm with **`y`** then **Enter**
4. Confirm a second time to start cloning

![Cloning in progress with Clonezilla](/img/blog/2025-11-30-reduire-disque-vm/clonezilla-progress.png)

**Estimated duration**: Between 10 and 30 minutes depending on data amount and Linstor DRBD storage speed.

## Step 5: Configure Boot on New Disk

Once cloning is complete:

1. **Shut down the VM** via Proxmox
2. Return to **Hardware** → **Options** → **Boot Order**
3. **Disable** CD-ROM (or remove ISO)
4. Make sure **scsi1** (new 135 GB disk) is in **first position**
5. **Start the VM**

### Boot Verification

The VM should boot normally on the new disk. Connect and verify:

```bash
sudo fdisk -l
```

![Final result: new 135 GiB disk active](/img/blog/2025-11-30-reduire-disque-vm/fdisk-final-result.webp)

**Checks**:
- `/dev/sdb` (new disk): **135 GiB** ✅
- `/dev/sda` (old disk): **400 GiB** (still present)
- Identical partitions on both disks

### Stability Test

Test your VM for **24-48 hours**:
- Verify all services start correctly
- Test critical applications
- Monitor system logs (`journalctl -xe`)

## Step 6: Delete the Old Disk

:::warning Wait before deleting
Only delete the old disk after **validating proper operation** of the VM for at least 24 hours. In case of problems, you can roll back.
:::

Once the VM is stabilized:

1. **Shut down the VM**
2. In Proxmox: **Hardware** → Select **Hard Disk (scsi0)** (400 GiB)
3. Click **Remove**
4. Confirm deletion

**Result**: 265 GB freed on Linstor DRBD storage! 🎉

## My Use Case: Proxmox Storage Reorganization

In my case, this operation allowed me to free up 265 GB on Linstor DRBD storage. With this reclaimed space, I can now repartition my physical disks on Proxmox hosts to optimize storage usage:

### Before

```
/dev/sda: 500 GiB
└── linstor_storage: 500 GiB (replicated storage)
```

### After

```
/dev/sda: 500 GiB
├── linstor_storage: 300 GiB (HA replicated storage)
└── local-lvm: 200 GiB (non-replicated local storage)
```

This reorganization allows me to better utilize resources:
- **Replicated storage** (Linstor DRBD - 300 GB): For critical VMs requiring high availability
- **Local storage** (local-lvm - 200 GB): Primarily for my Kubernetes VMs that manage distributed storage themselves via Longhorn, as well as some test VMs/LXCs

## Conclusion

Clonezilla allows efficient VM migration to a smaller disk, provided you:
1. **Shrink partitions beforehand** to leave free space
2. Use **KVM To RAM** mode to avoid display issues
3. Enable `-k0` and `-icds` options in Expert mode

This technique allowed me to free **265 GB** on my Linstor DRBD storage, optimizing Proxmox cluster resource usage and enabling more flexible storage reorganization.

## Resources

- [Official Clonezilla Documentation](https://clonezilla.org/clonezilla-live-doc.php)
- [Proxmox VE Documentation - Storage](https://pve.proxmox.com/wiki/Storage)
- [Article: Distributed Storage with Linstor DRBD on Proxmox](/blog/stockage-distribue-proxmox-ha)
- [Documentation: Current Homelab with Docker Compose](/docs/homelab-actuel)