In modern virtual infrastructure, speed, consistency, and repeatability are critical. Instead of installing and configuring every VM from scratch, administrators rely on VM templates — prebuilt golden images that can be cloned on demand.
One of the most powerful features in Proxmox VE is template-based cloning. But when you clone from a template, you must choose between:
- Full Clone
- Linked Clone
These two options look similar in the UI — but behave very differently in storage usage, performance, risk, and lifecycle management.
This extended guide covers:
- What Proxmox templates are
- Template creation workflow
- How cloning works internally
- Full clone vs linked clone differences
- Storage and performance tradeoffs
- Production best practices
- How to convert a linked clone into a full clone
What Is a Proxmox VM Template?
A template is a VM converted into a reusable master image. It typically contains:
- Installed operating system
- Latest updates and patches
- Base packages and tools
- Guest agent
- Baseline configuration
- Optional cloud-init setup
- Security hardening
Once converted to a template:
- It cannot be started directly
- It becomes read-only
- It is used only as a cloning source
- It ensures consistent deployments
Think of it as your golden image factory.
Standard Template Creation Workflow
Step 1 — Create Base VM
- Create VM
- Install OS
- Apply updates
- Install required packages
- Configure baseline settings
Step 2 — Prepare for Cloning
Recommended cleanup:
Linux:
- Clear logs
- Remove temp files
- Reset machine-id
- Remove SSH host keys (if not using cloud-init)
- Enable QEMU guest agent
Cloud-init images:
- Install cloud-init
- Set DHCP networking
- Reset instance data
Step 3 — Convert to Template
In Proxmox UI:
VM → More → Convert to Template
Template becomes your cloning source.
How Proxmox Cloning Works Internally
When you clone a template, Proxmox creates a new VM disk derived from the template disk.
Clone type determines how:
- Full clone → full disk copy
- Linked clone → snapshot + copy-on-write diff disk
This single choice affects storage, speed, safety, and flexibility.
Full Clone Explained
What Is a Full Clone?
A full clone creates a completely independent copy of the template disk.
Every block is duplicated.
The clone has:
- Its own disk
- No backing dependency
- Independent snapshots
- Independent lifecycle
Full Clone Characteristics
Storage
- Uses full disk space immediately
- 40 GB template → ~40 GB clone
Performance
- Direct disk reads/writes
- No backing-file lookup
- Predictable I/O
Portability
- Easy migration
- Easy backup
- Storage move supported
Safety
- Template can be deleted safely
- Snapshot chains are isolated
Full Clone Pros
- Production safe
- Fully independent
- Migration friendly
- Backup friendly
- Predictable performance
Full Clone Cons
- Slower to create
- Higher storage usage
- More initial disk I/O
Linked Clone Explained
What Is a Linked Clone?
A linked clone uses a snapshot of the template disk as a backing file.
Only changed blocks are stored in the clone disk using copy-on-write (CoW).
The clone disk stores:
- Differences only
- Reference to template snapshot
- Dependency chain
Linked Clone Characteristics
Storage
- Very space efficient
- Only changed data consumes space
Creation Speed
- Extremely fast
- No full disk copy required
Dependency
- Depends on template snapshot
- Template must not be removed
- Snapshot chain must remain intact
Performance
- Reads may traverse backing file
- Slight extra I/O overhead
Linked Clone Pros
- Very fast provisioning
- Minimal storage use
- Excellent for labs
- Great for CI/CD
- Ideal for disposable VMs
Linked Clone Cons
- Template dependency
- Risk if backing chain breaks
- More complex backups
- Not ideal for critical production
- Migration constraints
Full Clone vs Linked Clone — Comparison
| Feature | Full Clone | Linked Clone |
|---|---|---|
| Disk space | High | Low |
| Creation speed | Slower | Very fast |
| Template dependency | None | Required |
| Production use | Yes | Usually no |
| Lab/test use | Good | Excellent |
| Backup simplicity | Simple | More complex |
| Migration | Easy | Limited |
| Delete template safe | Yes | No |
| Performance predictability | High | Medium |
Storage Backend Requirements
Linked clones require snapshot-capable storage:
Supported:
- ZFS
- Ceph RBD
- LVM-thin
- QCOW2 directory storage
Not supported:
- Plain LVM
- Raw block storage without snapshots
Performance Behavior
Full Clone Path
VM → Own Disk → Storage
Simple and direct.
Linked Clone Path
VM → Diff Disk → Backing Snapshot → Storage
Extra lookup layer → small overhead → grows with heavy writes.
Converting a Linked Clone to a Full Clone
Can You Convert a Linked Clone to a Full Clone?
Yes — but not with a direct convert button.
Instead, you create a new full clone from the linked clone. This produces a fully independent VM disk and removes template dependency.
GUI Method
- Shut down the linked clone VM
- Right-click VM
- Click Clone
- Select:
- Full Clone
- Target storage
- New VM ID/name
- Click Clone
Result:
Template → Linked Clone → New Full Clone (independent)
The new VM no longer depends on the template snapshot chain.
CLI Method
qm clone <linked-vm-id> <new-vm-id> --full true --name new-full-vm
Example:
qm clone 210 310 --full true --name prod-web01
When You Should Convert
Convert linked → full when:
- Promoting to production
- Need independent backups
- Planning template cleanup
- Need predictable I/O
- Migrating storage
- Long-term VM lifecycle
Storage Impact Warning
Conversion will:
- Use full disk size
- Generate heavy read/write I/O
- Take longer than linked clone creation
Plan capacity first.
How to Check If a VM Is Linked
CLI:
qm config <vmid>
Look for:
backing file
base-xxx-disk
Indicates linked clone chain.
Production Best Practices
Use Full Clones For
- Production servers
- Databases
- Stateful workloads
- Long-lived VMs
- Critical services
- Migration targets
Use Linked Clones For
- Labs
- Training
- Testing
- CI pipelines
- Disposable workloads
- Classrooms
Template Hardening Checklist
Before template conversion:
- OS updated
- Guest agent installed
- Cloud-init configured (if used)
- Logs cleared
- Temp files removed
- Machine-id reset
- SSH keys removed
- Network verified
- Security baseline applied
Recommended Operational Strategy
Enterprise Pattern:
Versioned Templates
↓
Linked Clones → Dev/Test
↓
Full Clone → Production Promotion
Fast → efficient → safe promotion path.
Final Thoughts
Template cloning in Proxmox VE is one of the biggest operational accelerators available — but clone type matters.
Use this rule:
Must be reliable → Full Clone
Must be fast & cheap → Linked Clone
And remember:
Linked clones can always be promoted later by full-cloning them.
When used properly, templates + cloning deliver:
- Rapid VM rollout
- Standardized builds
- Lower admin effort
- Safer scaling
- Better lifecycle control