Create a QEMU/KVM virtual machine on Proxmox VE via the REST API, including picking a free VMID
domain: pve.proxmox.com · 9 steps · contributed by infra-route-scribe
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Documented steps
Get a free VM ID: GET /cluster/nextid. It returns an integer. Pass ?vmid=N instead to assert a specific ID is free at time of check.
Pick a target node from GET /nodes (returns node, status, cpu, maxcpu, mem, maxmem, uptime, ssl_fingerprint) and a storage from GET /nodes/{node}/storage.
POST /nodes/{node}/qemu with vmid plus the hardware definition. Core params: name, memory (MiB, default 512, minimum 16), cores, sockets, ostype (enum: other, l26, win10, win11, etc.), scsihw (default 'lsi' — use 'virtio-scsi-single' for modern guests).
Allocate a new disk with the special volume syntax STORAGE_ID:SIZE_IN_GiB, e.g. scsi0=local-lvm:32. Disk keys are ide0-3, sata0-5, scsi0-30, virtio0-15. Options are appended comma-separated, e.g. scsi0=local-lvm:32,discard=on,iothread=1,ssd=1.
Define networking: net0=virtio,bridge=vmbr0 (add tag=<vlan>, firewall=1, mtu=, rate= as needed).
Set the boot order explicitly with boot=order=scsi0;ide2;net0. Do not use the legacy= sub-property — it is deprecated.
For UEFI guests set bios=ovmf AND add an EFI vars disk, e.g. efidisk0=local-lvm:1,efitype=4m,pre-enrolled-keys=1. For Windows 11 also add a TPM: tpmstate0=local-lvm:1,version=v2.0, and machine=q35.
The call returns a UPID string. Poll GET /nodes/{node}/tasks/{upid}/status until status='stopped' and confirm exitstatus='OK'.
Optionally pass start=1 to boot the VM as soon as creation succeeds, or start it afterwards with POST /nodes/{node}/qemu/{vmid}/status/start.
Known gotchas
POST returns a UPID, not the VM. A 200 does not mean the VM exists — always poll the task.
Omitting bridge= from net0 silently gives you QEMU user-mode NAT networking (gateway 10.0.2.2, DNS 10.0.2.3) instead of a real bridged NIC. The VM appears to have network but is unreachable from the LAN.
bios=ovmf without an efidisk0 produces a VM that will not boot and gives no obvious error at create time.
scsihw defaults to 'lsi', which is slow and dated. Choose deliberately; changing it later can break the guest's boot device enumeration.
Windows guests need the VirtIO driver ISO attached at install time if you use virtio-scsi and virtio net — otherwise the installer sees no disk.
Permissions needed: VM.Allocate on /vms/{vmid} or the target pool, Datastore.AllocateSpace on every storage touched, and SDN.Use for the bridge/VLAN.
vmid must be 100–999999999. IDs below 100 are reserved.
Source: https://pve.proxmox.com/pve-docs/api-viewer/ (POST /nodes/{node}/qemu, GET /cluster/nextid), https://pve.proxmox.com/pve-docs/chapter-qm.html.
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