BASIC INFORMATION ABOUT IMAGES IN THE VCL

Notice: The VMware images were retired in August 2024 due to the Broadcom acquistion of VMWare and changes in the VMWare licensing as a result of the acquisition. VMWare has been replaced with KVM for virtual machines.

Creation

To create an image, you start by using a base image or another existing image as your “base”, install whatever applications or make whatever changes you want, then save it as a new image. You can also make updates to images you’ve created, and save the changes in a new version of that image. You identify which version of your image that you want to be the production version, i.e. the version that customers will get when they request that image.

When you first create an image, you are the only one that has access to it. In order to make it available for others to use, you must add it to an image group. Image groups can control who has access to an image, as well as what servers the image can be run on. There are two image groups to which all users have access by default, “allUsers” and “allUsers KVM“. The difference between these is based on the type of image: bare-metal or virtual.

Bare-Metal vs. Virtual

There are two types of images on the VCL: “bare-metal” or “full blade” images which use an entire physical server, and “KVM” or virtual images which run on virtual servers managed by the KVM Hypervisor. From the user perspective and an image administration perspective, there’s no difference in how you interact with them. However, they MUST be kept in separate groups. The bare-metal images are in “allUsers” which maps to run on full servers, and the KVM images are in “allUsers KVM” which maps to run on virtual machines.

Note It is preferable to create a KVM image, depending on the requirements of applications in the image. Load times for bare-metal images are typically around 20 minutes whereas vmware images load in around 6-8 minutes. This is due to the fact that there are several reboots during the imaging process, and a virtual machine reboot is software only. A bare-metal reboot is a hardware reboot of the server, resulting is a longer process.

In addition to much faster load times, there are more virtual machines available to run images than there are to run bare-metal images. If 10GB of RAM and 4 processors meet your needs, then a virtual machine is the way to go.

To create a bare-metal image, use an image that has “Full Blade” in its name. To create a virtual machine image, use an image that has the word “KVM” in its name. Also follow the convention by adding the word “KVM” or “Full Blade” to your image name. This makes them easy to identify. You can verify an image type by clicking Manage Images, choosing Edit Image Profiles, then Submit. Under the OS column, KVM images will show KVM in the OS name.

More On Groups

As mentioned above, image groups are used to map images to run on specific groups of hardware. There are also user groups which can be used to give sets of users access to different image groups. If you’d like to have a user group created for your image(s), please contact research@unc.edu.

For the general use hardware, there is an “allUsers” image group and a “allUsers KVM” image group for virtual, which any VCL user has access to. This group is mapped to the general research computing hardware.

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