Virtual Machines (VMs)

What is a VM?

From the Wikipedia entry for VMs: A virtual machine (VM) is a software-based emulation of a computer. Virtual machines operate based on the computer architecture and functions of a real or hypothetical computer.

Instances are another term for “virtual machine”.

VM Flavors

There are a number of “flavors” you can use when spinning up a VM. Below is a sample list of the specifications for each available OSDC instance. Note that the available flavors may vary from resource to resource, as more some resources provide options for VMs with higher RAM or Ephemeral Storage. VCPU indicates the number of cores activated when that flavor is used.

Some jobs may require larger instances, some may require a small instance, others may require multiple smaller instances. Your resource allocation quota will determine the size and quantity of instance you can spin up.

Flavor	VCPUs	VM Disk (GB)	RAM (GB)
m1.tiny	1	0	.5
m1.small	1	20	2
m1.medium	2	20	4
m1.large	4	20	8
m1.xlarge	8	20	16
m2.xlarge	8	20	32
m1.xxlarge	16	20	32
m2.xxlarge	16	20	64

Note

When you launch an instance in the Tukey Console, you’ll see in the lower left of the launch screen how much of your quota is in use. Any Instances you might attempt to launch beyond your given quota will fail to launch.

What is an Image?

A virtual machine image is a single file which contains a virtual disk that has a bootable operating system installed on it. Virtual machine images come in different formats. On the OSDC we use the term “Image” to denote the plain vanilla VMs we provide.

What is a Snapshot?

On the OSDC a “snapshot” preserves the state and data of a virtual machine at a given point in time. If a user installs software and packages on a plain vanilla image, they can take a snapshot so that new image can later be used by themselves or others.

On the OSDC you can publicly share your own snapshots or use already existing snapshots. This process will help users and labs from duplicating work. While currently in BETA, we’re working on making changes to the metadata associated with snapshots so that users can provide descriptions of the software packages, general purpose of the snapshot, and other helpful information.

Snapshotting Tip

Once a snapshot has completed in the OSDC console, we recommend launching a test version of that snapshot, and confirming its integrity before terminating the original VM that snapshot was taken from.

As a general rule of thumb, anything installed using apt-get will be saved during a snapshot. Almost anything on the filesystem that’s not in /tmp or /glusterfs will be saved. A helpful way to confirm that files in an image will snapshot correctly is is to run stat -c "%m" FILENAME. If the output is “/” then your files will snapshot correctly.

Warning

Snapshots are not backups. The snapshot file is only a change log of the original virtual disk, do not rely upon it as a direct backup process.

Launching an Instance in Tukey (General)

Launching an instance in Tukey is a relatively simple process. Below is a video on how to launch an instance from the Tukey console.

VIDEO: Launching an Instance

Terminating Instances

It’s important that OSDC users terminate VMs that are not in use. This helps ensure that resources will be available for all OSDC researchers and projects. To learn more about best practices regarding VMs please visit our FAQ/Best Practices section.

Reviewing Instance Status

Instance Status can be easily reviewed from both the command line and the console.

3 instance statuses - Terminating, Built, and Spawning