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300 lines
8.9 KiB
Markdown
---
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slug: reduire-taille-disque-vm-clonezilla
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title: Reducing VM Disk Size with Clonezilla
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authors: [tellserv]
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tags: [proxmox, clonezilla, virtualization, storage, linstor, drbd, disk-management]
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image: /img/blog/2025-11-30-reduire-disque-vm/clonezilla-logo.svg
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---
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import Tabs from '@theme/Tabs';
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import TabItem from '@theme/TabItem';
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<p align="center">
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<img src="/img/blog/2025-11-30-reduire-disque-vm/clonezilla-logo.svg" alt="Clonezilla Logo" width="300" />
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</p>
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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.
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<!--truncate-->
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:::danger MANDATORY BACKUP
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**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.
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📚 A detailed article on Proxmox Backup Server is coming soon.
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:::
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## Context
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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.
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### Problem
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After reducing the system partition to **130 GB** (leaving 270 GB of unallocated free space), I want to:
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1. Create a new **135 GB** disk (130 GB of data + 5 GB margin)
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2. Migrate the OS and data to this smaller disk
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3. Free up **265 GB** on Linstor DRBD storage
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### Final Goal
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Reorganize Proxmox hosts storage:
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- **300 GB**: Linstor DRBD (highly available replicated storage)
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- **200 GB**: local-lvm (non-replicated local storage)
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## Prerequisites
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### Required Tools
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- **Proxmox VE**: Virtualization hypervisor
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- **Clonezilla Live ISO**: Disk cloning tool ([download](https://clonezilla.org/downloads.php))
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- **Linstor DRBD**: Distributed storage (see [article on Proxmox distributed storage](/blog/stockage-distribue-proxmox-ha))
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### Initial VM State
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Before starting, check the current state:
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```bash
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sudo fdisk -l /dev/sda
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```
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**Expected output**:
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- Disk `/dev/sda`: **400 GiB**
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- System partition (`/dev/sda3`): **~120 GiB** used
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- Free space: **~270 GiB** unallocated
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:::tip Shrink partition beforehand
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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.
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:::
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## Step 1: Create the New Disk in Proxmox
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In the Proxmox web interface, access your VM configuration:
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1. Select your VM
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2. **Hardware** tab
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3. Click **Add** → **Hard Disk**
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**New disk configuration**:
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- **Storage**: `linstor_storage` (or your Linstor DRBD pool)
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- **Disk size**: `135 GiB`
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- **Bus/Device**: `SCSI` (scsi1)
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:::info
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The new disk will appear as `/dev/sdb` in the VM. The original disk `/dev/sda` remains in place for now.
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:::
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## Step 2: Mount the Clonezilla ISO
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Still in the Proxmox interface:
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1. Select the **Hardware** tab
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2. Double-click **CD/DVD Drive**
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3. **Storage**: `local` (or your ISO storage)
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4. **ISO image**: Select `clonezilla-live-3.3.0-33-amd64.iso`
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**Configure boot order**:
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1. **Options** tab → **Boot Order**
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2. Enable **CD-ROM** and place it in **first position**
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3. Click **OK**
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Start the VM via **Console** → **Start**.
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## Step 3: Start Clonezilla in KVM To RAM Mode
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:::warning Snow problem without KVM To RAM
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If you **don't** choose the **KVM To RAM** option, Clonezilla display will show snow (graphical artifacts) making the interface unusable.
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:::
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### Boot Mode Selection
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At Clonezilla boot:
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1. **First option**: Select **Clonezilla live (KVM To RAM, VGA 1024x768)**
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2. Press **Enter**
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### Clonezilla Initial Configuration
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Follow the configuration wizard:
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<Tabs>
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<TabItem value="language" label="Language">
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```
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Choose language: [en_US.UTF-8] English
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```
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</TabItem>
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<TabItem value="keymap" label="Keyboard">
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```
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Configuring console-data: [Don't touch keymap]
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```
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(or choose your keyboard layout)
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</TabItem>
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<TabItem value="mode" label="Clonezilla Mode">
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```
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Start Clonezilla: [device-device]
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```
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Select **device-device** (disk to disk clone)
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</TabItem>
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</Tabs>
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## Step 4: Clone Disk with Expert Options
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### Expert Mode Selection
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```
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Mode: [Expert mode]
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```
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Choose **Expert mode** to access necessary advanced options.
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### Operation Type Choice
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```
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Expert Mode: [disk_to_local_disk]
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```
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Select **disk_to_local_disk** (clone local disk to local disk).
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### Disk Selection
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1. **Source disk**: `/dev/sda` (400 GiB - old disk)
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2. **Destination disk**: `/dev/sdb` (135 GiB - new disk)
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:::danger Verify disks carefully
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**Warning**: Selecting the wrong disk will permanently erase your data! Check disk sizes before validating.
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:::
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### Critical Advanced Options
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Clonezilla offers several advanced options. **You MUST select**:
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#### Option 1: `-k0` (Create partition table proportionally)
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```
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-k, --create-partition-table
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[×] -k0 Create partition table in target disk proportionally
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```
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**Explanation**: This option recreates the partition table while keeping **original sizes** of partitions (not resizing them proportionally to the new disk).
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#### Option 2: `-icds` (Skip checking destination disk size)
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```
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-icds, --skip-check-dest-size
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[×] -icds Skip checking destination disk size before creating partition table
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```
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**Explanation**: By default, Clonezilla refuses to clone to a disk **smaller** than the source disk. This option disables this check.
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:::tip Why does it work?
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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.
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The `-k0` option ensures partitions keep their original size (130 GB) instead of being resized proportionally to the new disk.
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:::
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### Start Cloning
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1. Validate all options
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2. Clonezilla displays a **summary** of parameters
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3. Confirm with **`y`** then **Enter**
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4. Confirm a second time to start cloning
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**Estimated duration**: Between 10 and 30 minutes depending on data amount and Linstor DRBD storage speed.
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## Step 5: Configure Boot on New Disk
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Once cloning is complete:
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1. **Shut down the VM** via Proxmox
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2. Return to **Hardware** → **Options** → **Boot Order**
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3. **Disable** CD-ROM (or remove ISO)
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4. Make sure **scsi1** (new 135 GB disk) is in **first position**
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5. **Start the VM**
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### Boot Verification
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The VM should boot normally on the new disk. Connect and verify:
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```bash
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sudo fdisk -l
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```
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**Checks**:
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- `/dev/sdb` (new disk): **135 GiB** ✅
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- `/dev/sda` (old disk): **400 GiB** (still present)
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- Identical partitions on both disks
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### Stability Test
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Test your VM for **24-48 hours**:
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- Verify all services start correctly
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- Test critical applications
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- Monitor system logs (`journalctl -xe`)
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## Step 6: Delete the Old Disk
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:::warning Wait before deleting
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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.
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:::
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Once the VM is stabilized:
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1. **Shut down the VM**
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2. In Proxmox: **Hardware** → Select **Hard Disk (scsi0)** (400 GiB)
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3. Click **Remove**
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4. Confirm deletion
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**Result**: 265 GB freed on Linstor DRBD storage! 🎉
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## My Use Case: Proxmox Storage Reorganization
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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:
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### Before
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```
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/dev/sda: 500 GiB
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└── linstor_storage: 500 GiB (replicated storage)
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```
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### After
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```
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/dev/sda: 500 GiB
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├── linstor_storage: 300 GiB (HA replicated storage)
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└── local-lvm: 200 GiB (non-replicated local storage)
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```
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This reorganization allows me to better utilize resources:
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- **Replicated storage** (Linstor DRBD - 300 GB): For critical VMs requiring high availability
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- **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
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## Conclusion
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Clonezilla allows efficient VM migration to a smaller disk, provided you:
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1. **Shrink partitions beforehand** to leave free space
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2. Use **KVM To RAM** mode to avoid display issues
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3. Enable `-k0` and `-icds` options in Expert mode
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This technique allowed me to free **265 GB** on my Linstor DRBD storage, optimizing Proxmox cluster resource usage and enabling more flexible storage reorganization.
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## Resources
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- [Official Clonezilla Documentation](https://clonezilla.org/clonezilla-live-doc.php)
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- [Proxmox VE Documentation - Storage](https://pve.proxmox.com/wiki/Storage)
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- [Article: Distributed Storage with Linstor DRBD on Proxmox](/blog/stockage-distribue-proxmox-ha)
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- [Documentation: Current Homelab with Docker Compose](/docs/homelab-actuel)
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