The majority of the [Packer Builders](../../docs/builders/index.html) can run in a container or VM, a common model used by most CI/CD services. However, the [QEMU builder](../../docs/builders/qemu.html) for [KVM](https://www.linux-kvm.org/page/Main_Page) and [Xen](https://www.xenproject.org/) virtual machine images, [VirtualBox builder](../../docs/builders/virtualbox.html) for OVA or OVF virtual machines and [VMWare builder](../../docs/builders/vmware.html) for use with VMware products require running on a bare-metal machine.
The [Building a VirtualBox Image with Packer in TeamCity](./building-virtualbox-image.html) guide shows how to create a VirtualBox image using TeamCity's support for running scripts on bare-metal machines.