VM Cloning Overview

Virtual machines play an important role in today’s software environments. Put simply, a virtual machine is a software emulation of a hardware system. Hyper-V and VMware are the two most popular virtual machine platforms. As a managed services provider (MSP), you’ll be tasked with configuring virtual machines for your clients—VM cloning is an easy way to create virtual machines. In this article, we’ll explain how to clone a virtual machine and why this method is so useful.

What is VM cloning?

A VM clone is a copy of a virtual machine. The existing virtual machine is known as the parent, while the new VM is called the clone. After the cloning operation, the clone VM runs as a separate virtual machine.

Why would you need to clone a virtual machine? Cloning is a fast and simple way to create a new virtual machine that shares properties with an existing one. The process of installing a guest operating system and programs from scratch can take a great deal of time. Using cloning, you can perform installation and configuration once, and then use the clone as a basis for many future virtual machines.

VM cloning is most useful for deploying multiple identical virtual machines to a group of users. For example, a sysadmin can clone a virtual machine for each employee in a particular department—since the employees use the same applications, their setups should be the same. Similarly, a teacher may wish to clone a virtual machine for each student, with lesson materials and programs preinstalled. VM cloning is also helpful for software testing. Testers can clone a development environment and use it as a baseline for comparison while testing.

There are two types of VM clones: full clones and linked clones. A full clone is a completely separate copy of a VM that shares no system resources with the parent once it’s running. A linked clone, on the other hand, continues to share virtual disks with the parent after it’s created. Since it runs independently, a full clone generally has faster performance than a linked one. However, a full clone can take longer to create, with delay times of up to a few minutes when file sizes are large. Linked clones are faster to create and have the advantages of saving disk space by allowing multiple VMs to run off a single software installation.

What is the difference between a clone and a snapshot in VMware?

VMware allows users to create either a clone or a snapshot of a virtual machine. A snapshot preserves the current state of a virtual machine, copying the VM’s disk file. It is used for backup purposes. If you need to save the configuration of a virtual machine so you can revert back to it later if something goes awry, create a snapshot. A clone, by contrast, is an entirely separate copy of the VM. If you need to make a new VM that will run independently, cloning is the only way to go.

Can I clone a VM while it is running?

Whether you can clone a virtual machine while it’s running depends on the version of your software. VMware VirtualCenter 2.5 Update 2 and later versions allow you to perform a live cloning operation, copying a virtual machine as it runs. However, in earlier versions, you’ll need to power off the virtual machine before trying to clone it.

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