Guide · Virtualisation
Backing up Proxmox VE: VMs consistent, encrypted, off-site
In short: always back up a Proxmox VM as a whole – all disks at the same point in time, plus configuration, UEFI variables and vTPM. With the QEMU guest agent the backup becomes file-system-consistent. And at least one copy belongs off-site, encrypted.
What belongs to a VM
A VM consists of more than its system disk. A complete restore needs:
- all virtual disks, captured at the same point in time – otherwise the database and log disks do not match;
- the VM's configuration: processors, memory, network adapters, firmware;
- for UEFI systems, the EFI disk with the UEFI variables;
- for Windows 11 and BitLocker, the vTPM state – without it the system does not start or asks for the recovery key.
Consistent rather than merely “crash-safe”
If a running VM is backed up without preparation, the result is like a hard power-off: it usually starts, but open files and databases may be incomplete. With the QEMU guest agent, the file systems in the guest can be frozen briefly until the snapshots of all disks are in place. How long the guest was frozen should be stated in the backup log.
For this, the package qemu-guest-agent (on Windows the VirtIO guest tools) must be installed in the VM and enabled in Proxmox under Options → QEMU Guest Agent.
Storage types and snapshots
| Storage | How the snapshot is created |
|---|---|
| LVM, LVM-thin | LVM snapshot of the volume |
| ZFS | ZFS snapshot of the zvol, read via a clone |
| qcow2 file (directory, NFS, CIFS) | internal snapshot in the image; for a running VM via QEMU for all disks together |
| Ceph RBD | RBD snapshot, read via the kernel client – also for external clusters |
Don't forget the off-site copy
A backup on storage in the same cluster protects against operating errors, but not against fire, ransomware or a compromised administrator account. Following the 3-2-1-1-0 rule, one copy belongs at another location and one locked as immutable – encrypted before it leaves the host.
How AegisGrid backs up Proxmox VE
AegisGrid runs directly on the Proxmox host and backs up a VM in one run with all disks, EFI disk, vTPM state and configuration – on LVM, LVM-thin, ZFS, Ceph RBD and qcow2. With the guest agent it freezes all disks together and keeps the window as short as possible; without the guest agent it backs up crash-consistently and notes this in the log. Thanks to change tracking (CBT), follow-up backups read only what the guest has written since the last backup. The data is deduplicated and encrypted and can go to up to eight destinations in one run. Restores are made as a new VM, disk by disk or in place over the existing VM, also directly from the backup server. The backup server can also regularly start the VMs as a test in an isolated environment.
Frequently asked questions about Proxmox backup
Do I have to shut down the VM for the backup?
No. Running VMs are backed up via snapshots. With the QEMU guest agent, the file systems in the guest are frozen only briefly for this.
Does every backup have to read the whole VM?
No. After the first backup, QEMU keeps track of which areas the guest has written, and AegisGrid reads only those. The whole VM is read again after a restart or migration of the VM, after a disk has been enlarged and whenever there is any doubt – with a plain note in the log.
What happens to disks on iSCSI?
AegisGrid does not back up disks directly on iSCSI or larger raw and vmdk files. If a VM has such a disk, it is rejected with a clear message instead of being backed up incompletely; in Proxmox the disk can be moved to qcow2, ZFS or LVM-thin with “Move Storage”.
Can I restore a VM on a different host?
Yes. The backup contains the VM's configuration; it is restored as a new VM, if you wish with a different VMID, different storage and new or the original MAC addresses.
Can I reset a VM to an earlier version?
Yes, in place: the VM keeps its VMID. Its disks are first written next to the existing ones and switched over only after success; the previous ones are kept. If there is no room for a second copy, AegisGrid writes directly into the existing disks, optionally only the changed blocks.
Back up your Proxmox environment
In a pilot project we check in advance whether all your VMs and storage types are covered.