> For the complete documentation index, see [llms.txt](https://docs.platform9.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.platform9.com/private-cloud-director/virtualized-clusters/virtualmachine/flavorless-vms-with-hot-plug.md).

# Flavorless VM Support

Although using flavors to create virtual machines is a fundamental feature of <code class="expression">space.vars.product\_name</code>, many organizations (especially those moving away from traditional virtualization vendors) may prefer a simpler process that doesn’t require specifying a flavor when creating a VM.

## Zero-Size Flavor

To support this scenario, Private Cloud Director allows creation of VMs using a **special zero-size flavor**, where both the **number of vCPUs and the RAM are set to zero**. Private Cloud Director ships out of the box with one such flavor, but you can also create new flavors where the number of vCPUs and the RAM are set to zero.

When you choose such a flavor when creating a new VM, you can then specify the amount of CPU and Memory that the VM should get provisioned with.

Using the zero-size flavor is a requirement in order to use CPU or memory hot-add feature

## Create a Zero-Size Flavor

1. In the Private Cloud Director UI, navigate to Virtual Machines ▷ Flavors and click Create Flavor.
2. **Enable Hotplugging**: toggle **on**.
3. Set a Disk size.
4. *(Optional)* Add Metadata if you want Private Cloud Director to place VMs on specific host aggregates.
5. Check the Make Public checkbox if you would like to make this flavor available to all tenants.
6. Click Create Flavor.

## Deploy a VM with a Zero-Size Flavor

You can create a hot-add-capable VM directly from the **Deploy New VM** wizard by selecting a zero-size flavor during flavor selection.

1. Go to Virtual Machines ▷ Virtual Machines and click Deploy New VM.
2. During Flavor selection: enable the **Hot-plug Compatible** toggle to filter the list.
3. Choose the zero-size flavor you created above.
4. In the **Hotplug RAM** and **Hotplug vCPUs** fields, enter the initial resources you would like to create this VM with. In the **Hotplug RAM Maximum** and **Hotplug vCPUs Maximum** fields, enter the most memory and vCPUs you plan to hot-add. Both RAM fields have a MiB/GiB unit selector that defaults to MiB. The wizard pre-fills 65536 MiB and 64 vCPUs as the maximums, and you cannot change the maximums after the VM is created. For how the maximum affects host memory use, see [Known Issues](/private-cloud-director/virtualized-clusters/virtualmachine/vm-hot-add-cpu-or-memory.md#known-issues).
5. Finish the remaining steps and deploy the VM.

Private Cloud Director will create the VM with the requested CPU and Memory resources.

## Hot-add CPU or Memory to a Running VM

Read [VM Hot-Add CPU Or Memory](https://platform9.com/docs/private-cloud-director/2025.8/private-cloud-director/cpu-memory-hot-add-support) about how to hot add resources to a running VM.

## Use Flavorless VM with CLI

To automate creation of flavorless VM using CLI, API or terraform provider, use the zero-size flavor when creating the VM and use the following values for the metadata fields.

{% tabs %}
{% tab title="Bash" %}

```bash
{
    "HOTPLUG_MEMORY": "<specify memory in MiB for the VM>",
    "HOTPLUG_MEMORY_MAX": "<specify maximum memory in MiB for the VM>",
    "HOTPLUG_CPU": "<specify number of VCPUs for the VM>",
    "HOTPLUG_CPU_MAX": "<specify maximum number of VCPUs for the VM>"
}
```

{% endtab %}
{% endtabs %}

If you omit `HOTPLUG_MEMORY_MAX` and `HOTPLUG_CPU_MAX`, the VM's maximum is the host's total memory and vCPU count. You cannot add or change `HOTPLUG_MEMORY_MAX` or `HOTPLUG_CPU_MAX` after the VM is created.

## Limitations & Best Practices

* VM disk size **cannot** be changed via the hot-add feature.
* On Windows Server 2019, Windows Server 2022, and Windows 11 guests, the guest OS can report the Hotplug RAM Maximum as installed memory. See [Known Issues](/private-cloud-director/virtualized-clusters/virtualmachine/vm-hot-add-cpu-or-memory.md#known-issues).


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