In SkyHiGh all virtual machines boots from images which is stored in the openstack image service (glance). Manipulation of these images is done trough the use of the glance client or trough the web interface. This page explains the glance client:
Image formats
As SkyHiGh utilizes KVM for the virtualization, a large range of image formats are supportet (vhd, vmdk, vdi, iso, qcow2, aki, ari, ami, raw). The preferred format is however raw images, as this enables the compute-node to create a root-disk for the virtual machine which is a COW (Copy-on-write) snapshot of the original image. This way it is not needed to take a full image before the virtual machine is booted. This speeds up the VM boot process a lot.
Determine image format
To determine what format a certain image is, qemu-img can be used like so:
$ qemu-img info trusty-server-cloudimg-amd64-disk1.img
image: trusty-server-cloudimg-amd64-disk1.img
file format: qcow2
virtual size: 2.2G (2361393152 bytes)
disk size: 248M
cluster_size: 65536
Format specific information:
compat: 0.10
refcount bits: 16
Converting images
To convert images to the raw format, the utility "qemu-img" can be used:
$ qemu-img convert -f <original_image_type> -O <converted_image_type> <original_image> <converted_image>
So, to convert the qcow2 image "debian-8.2.0-openstack-amd64.qcow2" to a raw image, the following command could be used:
$ qemu-img convert -f qcow2 -O raw debian-8.2.0-openstack-amd64.qcow2 debian-8.2.0-openstack-amd64.raw
Uploading new images
To upload a new image to glance, the following command can be useful:
glance image-create --name <image_name> --file <image_location> --disk-format raw --container-format bare --is-public True --progress
For example, the following command would upload an ubuntu image:
glance image-create --name "Ubuntu Server 16.04 (Xenial) amd64" --file xenial-server-cloudimg-amd64-disk1.img.raw --disk-format raw --container-format bare --is-public True --progress
The "–is-public True" flag is used to indicate that all tenants should have access to this image, and the upload would then require admin credentials. In the case of an image upload which should only be accessible to the tenant uploading it, that flag can be omitted.