Openstack

openstack and the cloud

Openstack is a popular, powerful open-source virtualisation environment supported by numerous providers. In openstack, machines are provisioned from images that are pre-built and uploaded to the hosting provider. these images can have certain artifacts such as their CPU and RAM increased or decreased, as well as their total allocable disk space. Openstack hosting providers differ in several key ways from traditional shared, or KVM hosting providers in that:

• openstack images are expected to arrive pre-built. you cannot build a gentoo image from system rescue cd at the providers panel.
• static assignment of IP addresses is often not supported, however the IP your host receives by DHCP generally does not change
• resouces such as extra disks, nics, switchports, and even routers can be granularly controlled with some providers.
• VIRTIO drivers replace conventional hardware.
• EFI is generally not supported, although openstack provides this support should you choose to create your own image.

creating the build environment

the following packages should be emerged to create a KVM guest.

emerge libvirt virt-manager virt-viewer libguestfs

pay close attention to the build flags for libguestfs, as it requires caml support in order to emerge the full toolset and will silently omit packages without it.

configure your kernel to support VIRTIO devices. many references are vague as to the specific packages and encourage selecting all of them. search for these packages in menuconfig to determine which ones youll use, and which you do not need. debug logging from a KVM guest generates substantial overhead. The following are minimum configured VIRTIO drivers to ensure a successful boot.

CONFIG_VIRTIO=y
CONFIG_VIRTIO_PCI=y
CONFIG_VIRTIO_PCI_LEGACY=y
CONFIG_VIRTIO_BALLOON=y
CONFIG_VIRTIO_INPUT=y
CONFIG_VIRTIO_MMIO=y
CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=y