P2V: convert a physical server into a virtual machine

Old physical servers often run software nobody wants to reinstall. A physical-to-virtual (P2V) migration copies the whole machine into a VM, so you can retire the hardware while keeping the system running, with snapshots and backups on top.

Before you start

• A KVM or Proxmox host with enough space; see install KVM.
• A maintenance window; for consistency, image the disks while the OS is shut down (boot a live USB).
• A full backup of the physical server.
• Check software licences that are bound to hardware (some re-activate after moving).

Option 1: image with dd over SSH

Boot the physical server from a Linux live USB, then stream the disk to the KVM host:

dd if=/dev/sda bs=4M status=progress | gzip -1 | ssh root@kvm1 "gunzip | dd of=/var/lib/libvirt/images/oldsrv.raw bs=4M"

Then convert to qcow2 to save space:

qemu-img convert -p -O qcow2 oldsrv.raw oldsrv.qcow2

Option 2: Clonezilla

Clonezilla images the used blocks only and can restore into an empty VM disk. Save an image to an SSH or NFS share, create a VM with a disk at least as large as the original, boot Clonezilla in the VM and restore.

Option 3: virt-p2v

The libguestfs project's virt-p2v boots on the physical machine and sends it to a conversion server running virt-v2v, which also injects VirtIO drivers. Useful for Windows and RHEL-family systems.

Create and boot the VM

virt-install --name oldsrv --memory 4096 --vcpus 2 --disk /var/lib/libvirt/images/oldsrv.qcow2,bus=sata --import --os-variant generic --network bridge=br0,model=e1000e --graphics vnc,listen=127.0.0.1 --noautoconsole

Start with SATA disk and e1000e network for compatibility, and match BIOS vs UEFI to the original (add --boot uefi if it used UEFI).

Fix things after first boot

• Linux: rebuild the initramfs with VirtIO modules, switch to VirtIO devices, update network interface names and fstab (use UUIDs).
• Windows: install virtio-win drivers, then switch to VirtIO; see Windows VMs on KVM.
• Remove hardware vendor agents (RAID tools, IPMI drivers) that no longer apply.
• Install the QEMU guest agent.
• Shrink oversized disks later if needed, and right-size CPU/RAM.

Troubleshooting

• Boots to "no bootable device": firmware mismatch or the wrong disk was imaged.
• Kernel panic "unable to mount root": missing storage driver; use SATA and rebuild initramfs.
• Windows INACCESSIBLE_BOOT_DEVICE: boot with SATA, install VirtIO drivers, then switch.
• IP conflict: keep the physical server offline or change one IP.

Frequently asked questions

Can I do P2V without downtime?

Live imaging is possible with some tools, but a shutdown gives a consistent copy.

Is it better to rebuild?

Rebuilding on a fresh OS is cleaner long-term; P2V is a pragmatic step for legacy systems.

Does Proxmox support importing the disk?

Yes, use qm importdisk with the converted image.

Next steps

• Convert VM disks to qcow2
• VirtIO drivers
• Back up KVM VMs