What is a Snapshot in Proxmox?
A snapshot in Proxmox VE is a point-in-time image of a virtual machine (VM) or container (CT), including:
- The VM/CT configuration
- Disk state
- Memory (optional)
Think of it like hitting “pause and save” on a machine — you can revert to that exact state later if needed.
Types of Snapshots in Proxmox
| Snapshot Type | Description |
|---|---|
| Internal (live) | Stored inside the VM’s disk backend (e.g., QCOW2, ZFS, LVM-thin, Ceph RBD) |
| With memory | Includes RAM state; VM resumes exactly as it was |
| Without memory | Just disk and config; on restore, the VM boots fresh |
Requirements for Snapshots
Not all storage types support snapshots.
| Storage Type | Snapshot Support | Notes |
|---|---|---|
| ZFS | Yes | Fast, efficient block-level snapshots |
| LVM-Thin | Yes | Supports internal snapshots |
| Ceph RBD | Yes | Block-level snapshots |
| QCOW2 | Yes | File-level snapshot (can grow over time) |
| RAW on LVM | No | Requires full clone instead |
When to Use Snapshots
- Before OS updates, application installs, or system changes
- Before major reconfiguration or troubleshooting
- For development/testing environments
- Creating golden images/templates
Snapshot Limitations
- Not a backup: Snapshots live on the same disk. If the disk fails, snapshot is lost.
- Performance overhead: Especially on
qcow2, performance can degrade over time. - Storage usage grows: As changes are made after the snapshot, disk usage increases.
- Can’t move VMs with snapshots: You must delete snapshots to migrate VMs between storage types.
How to Use Snapshots in Proxmox
Create a Snapshot (GUI):
- Go to your VM or CT
- Click “Snapshots”
- Click “Take Snapshot”
- Name it, and check “Include RAM” if needed
- Confirm
Restore Snapshot (GUI):
- Go to the VM > Snapshots
- Select the snapshot
- Click “Rollback” (Warning: overwrites current state)
CLI Examples:
# Take snapshot
qm snapshot 100 pre-update-snapshot --description "Before patching"
# Snapshot with RAM
qm snapshot 100 with-ram --vmstate 1
# List snapshots
qm listsnapshot 100
# Rollback to snapshot
qm rollback 100 pre-update-snapshot
For containers (CTs), use pct instead of qm:
pct snapshot 101 test-snap
pct rollback 101 test-snap
Best Practices
- Limit number of active snapshots: 1–2 max for production VMs
- Avoid long-term snapshot use: Can cause disk bloat and performance issues
- Use Proxmox Backup Server (PBS) for proper backups
- Test snapshot and rollback process on non-production VMs first
- Monitor ZFS/LVM usage if snapshotting often
Snapshot vs Backup in Proxmox
| Feature | Snapshot | Backup |
|---|---|---|
| Speed | Instant | Slower (depending on size) |
| Storage | On same disk | Stored elsewhere (e.g., PBS) |
| Survivability | Lost if disk/storage fails | Safe (if backup is external) |
| Use case | Quick rollback, testing | Disaster recovery, archiving |
Conclusion
Snapshots in Proxmox VE are a powerful, lightweight tool to protect against misconfiguration, errors, or failed upgrades. However, they are not a substitute for backups and should be used strategically and temporarily.
- For critical systems: Take a snapshot before major changes, then delete after confirming success.
- For developers: Use snapshots to quickly test and revert code or OS builds.
- For admins: Pair snapshots with proper off-site backups using Proxmox Backup Server.
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