Parent page: Cloud

Images are files which contain the contents of a virtual disk. Images often contain a base operating system used to create a volume or an ephemeral disk from which a virtual machine boots. An ephemeral disk is a virtual disk file which resides on the host (or hypervisor) where the virtual machine runs. Ephemeral disk files are destroyed when a VM is destroyed, in contrast to volumes. Images are portable in that they can be downloaded from the cloud, used to create a virtual machine using virtual box or similar on your laptop, and uploaded to another cloud and used to create a new virtual machine. This is not the case with volumes or ephemeral disks. Images come in a variety of formats. Some commonly encountered formats are: raw, qcow2, vmdk, and vdi.

Warning

If sharing your virtual machine images, be sure to remove sensitive information such as public/private keys, configuration files containing passwords, etc. If uploading an image created from a VirtualBox virtual machine to our clouds, it must have cloud-init installed and configured correctly (see OpenStack docs on creating images manually for more details).

For a list of images provided by our staff, see images.

Creating an image from a VM¶

The procedure for creating an image of a VM depends on whether it is booting from a volume (typically "p" flavours), or from an ephemeral disk (typically "c" flavours).

If booting from an ephemeral disk¶

The OpenStack command line clients can be used with the command:

openstack server image create <server-name>

where <server-name> should be replaced with the name of your server. This action will only include the VM's root drive (e.g. /dev/vda) in the image. Ephemeral drives and non-boot attached volumes will not be included in the image, so additional measures should be taken to preserve this data.

Tip

We recommend the VM be shut off (not deleted) before an image is created from it. If the VM is writing to disk while the image is being created, the filesystem may be captured in an inconsistent state.

If booting from a volume¶

See Creating an image from a volume.

Sharing an image with another project is a two-step process.

A member of the project owning the image must share it with a second project.
A member of the second project must accept the newly shared image.

To share an image a member in the project owning the image uses the OpenStack command below.

[name@server]$  glance member-create <IMAGE_ID> <MEMBER_ID>
+------------+-------------+---------+
| Image ID   | Member ID   | Status  |
+------------+-------------+---------+
| <IMAGE_ID> | <MEMBER_ID> | pending |
+------------+-------------+---------+

where <IMAGE_ID> is the ID of the image to be shared, and <MEMBER_ID> is the ID of the project to share it with.

To accept the shared image a member in the second project uses the OpenStack command below.

[name@server]$  glance member-update <IMAGE_ID> <MEMBER_ID> <MEMBER_STATUS>
+------------+-------------+----------+
| Image ID   | Member ID   | Status   |
+------------+-------------+----------+
| <IMAGE_ID> | <MEMBER_ID> | accepted |
+------------+-------------+----------+

where <IMAGE_ID> is ID of the image to update, <MEMBER_ID> is the ID of the second project, and <MEMBER_STATUS> is the new status of the image. Valid values for status are accepted, rejected, and pending. The image will then be available for use and appear in the OpenStack dashboard's list of images in the second project.

To check the status of image membership use the following command.

[name@server]$ glance member-list --image-id <IMAGE_ID>
+------------+-------------+----------+
| Image ID   | Member ID   | Status   |
+------------+-------------+----------+
| <IMAGE_ID> | <MEMBER_ID> | accepted |
+------------+-------------+----------+

Downloading an image¶

The first step is to install the OpenStack client and download the OpenStack RC file and source it (see OpenStack command line clients). The OpenStack client can list the available images on your OpenStack project with

openstack image list

producing something like:

ID	Name	Disk Format	Container Format	Size	Status
982761b2-c77b-4852-8ae3-bf98b32b8894	Hadoop-2.2.4	qcow2	bare	10253107200	active
b7bd3033-9836-406d-a8f2-2e91978026b4	hadoopmaster	qcow2	bare	3493527552	active
2c751755-854d-49c3-af82-d501e51e7159	hadoopmaster-active	qcow2	bare	13134004224	active
c41012f4-ed82-4478-a81f-5efb96a31b1a	hadoopmaster-old	qcow2	bare	3493527552	active
78e61a3f-b546-441a-b476-a7077b04ca36	hadoopslave	qcow2	bare	3490971648	active
516845c3-b256-4c6d-a2cb-e31e822c7e34	hadoopslave1-active	qcow2	bare	8345026560	active
1546bd86-5314-4fce-9576-e2f6930dad30	hadoopslave1-old	qcow2	bare	3490971648	active
baf78e8d-8288-4854-a66b-812cdf3ccbca	TestVM	qcow2	bare	13167616	active
2faf97d7-5b0b-44ce-8024-3bef5a634570	test_ubuntu_initial	qcow2	bare	1799487488	active
308b6614-396a-4360-9c33-4e86f41ea0ec	trusty	qcow2	bare	256180736	active
9b3c3fda-2aca-43b5-a3e7-662a94f5e7fb	Ubuntu_14.04_Trusty-amd64-20150708	qcow2	bare	257884672	active
f93e66cf-fec1-4460-8fc7-506e716fbf30	ucernvm-prod.1.18-10	raw	bare	20971520	active

Note

You may need an additional option(s), such as --long, to see all the columns above depending on the version of the client you are using.

You can then download a particular image with

openstack image save --file ./<file-name-for-image>.<format> <ID>

where <format> matches the value in the Disk format column and <ID> matches the value in the ID column.

Uploading an image¶

The first step is to install the OpenStack client and download the OpenStack RC file and source it (see OpenStack command line clients). Then run the command

openstack image create --file <path-to-local-file-image> --disk-format <format> <new-image-name>

where * <path-to-local-file-image> is the path to the file containing the image you wish to upload from your local machine, * <format> is the disk format; if not specified, the raw format is assumed. If your image isn't raw format this will cause issues, and you must choose a format that matches the format of your image. * <new-image-name> is the name of the image as it appears on the OpenStack dashboard.

Creating a VirtualBox VM from a cloud image¶

VirtualBox is a software package which allows you to create and run virtual machines on your desktop or laptop. It can be run on many different operating systems (Windows, Linux, Mac) and the virtual machines it creates may run one of many different operating systems.

To use a QCOW2 image downloaded from an OpenStack cloud, as shown above, with VirtualBox you will need to convert the image in the qcow2 format to the vmdk format. This can be done with the qemu-img tool. This can be installed with something like

sudo apt-get install qemu-utils

(previously the package was called qemu-img) then do the conversion with

qemu-img convert -f qcow2 vdisk.qcow2 -O vmdk vdisk.vmdk

You can then create a new virtual machine and attach the vmdk image to it (see how to run a vmdk file in VirtualBox for detailed instructions on this).