Cloud computing environments like Jetstream2 rely on the concepts of images and instances. An image is a template for a virtual machine (VM) that can be used to create one or more instances of that VM. An instance is a runnable VM that can be turned on and off and that you can log in to.

Images

Jetstream2 provides several different types of images, including those based on the Ubuntu, Rocky Linux and AlmaLinux Linux flavors. Jetstream2 maintains a list of current featured images, which will change over time. Microsoft Windows images are not currently supported on Jetstream2.

These images contain bare operating systems, without any software installed. However, Jetstream2 mounts a remote disk on each instance, with that disk containing a software collection . This software collection is expected to grow and change over time. Users are welcome to install other software on their instances, though they will be responsible for providing their own licenses for such software.

You can create your own image by taking a snapshot of an existing instance that was customized after its creation. This image will know about all of the instance's users and configurations, and will retain all of the installed software and data files. Such an image can then be used to clone additional instances of that customized configuration.

Instances

At the time of its creation, an instance is assigned a VM size, or flavor. Flavors govern the number of CPU cores, amount of RAM, and presence and size of any graphics processing unit (GPU) in the instance. They also dictate an instance's hourly operating costs in Jetstream2 "service units" (SUs). Jetstream2's VM sizes and costs are subject to change. For standard flavors, an active VM's cost in SUs is typically equal to its number of cores. But if your flavor includes a large amount of memory of an attached GPU, the cost structure will be different. An instance's flavor can be changed after its creation to meet your changing needs.

Once an instance has been created from an image, it can be shelved and unshelved as you see fit, which is much like powering a physical computer off and on. Instances only incur SU costs when they are running, so shelving them save your SUs when you are not actively using the instance. Shelving and unshelving instances are discussed in Managing Instances.

All instances created through Exosphere include operating system packages to support a graphical environment, allowing you to use the VM's "desktop" to run software with a graphical user interface (GUI). You can access this graphical environment using Exosphere's Web Desktop functionality, described in the Logging in to an Instance section.