A virtual machine is a software computer that runs a guest operating system. Virtual machines are comprised of a set of configuration files and data files stored on local or remote storage. These configuration files contain information about the virtual hardware presented to the virtual machine. This virtual hardware includes the CPU, RAM, disk controllers, removable devices, and so on, and emulates the same functionality as the physical hardware. The following screenshot depicts the virtual machine files that are stored on a shared Network File System (NFS) datastore:
The files that make up a virtual machine are typically stored in a directory set aside for the particular virtual machine they represent. These files include the configuration file, virtual disk files, NVRAM file, and virtual machine log files.
The following table lists the common virtual machine file extensions along with a description of each:
| File extension | Description |
| .vmx | This is a virtual machine configuration file. It contains the configurations of the virtual hardware that is presented to the virtual machine. |
| .vmdk | This is a virtual disk descriptor file. It contains a header and other information pertaining to the virtual disk. |
| -flat.vmdk | This is a preallocated virtual disk. It contains the content or data on the disk used by the virtual machine. |
| .nvram | This is a file that stores the state of a virtual machine's Basic Input Output System (BIOS) or Extensible Firmware Interface (EFI) configurations. |
| .vswp | This is a virtual machine swap file. It gets created when a virtual machine is powered on. The size of this file is equal to the amount of memory allocated minus any memory reservations. |
| .log | This is a virtual machine log file. |
| .vmsd | This is a virtual machine file used with snapshots to store data about each snapshot active on a virtual machine. |
| .vmsn | This is a virtual machine snapshot data file. |
Virtual machines can be deployed using a variety of methods, as follows:
- Using the New Virtual Machine Wizard in the vSphere Client or vSphere Web Client
- By getting converted from a physical machine using the VMware Converter
- By getting imported from an Open Virtualization Format (OVF) or Open Virtualization Archive (OVA)
- By getting cloned from an existing virtual machine
- By getting deployed from a virtual machine template
When a new virtual machine is created, a guest operating system can be installed on the virtual machine. VMware vSphere 6.7 supports more than 120 different guest operating systems. These include many versions of the Windows server and desktop operating systems, many distributions and versions of Linux and Unix operating systems, and Apple macOS operating systems.
Virtual appliances are preconfigured virtual machines that can be imported to the virtual environment. A virtual appliance can be comprised of a single virtual machine or a group of virtual machines with all the components required to support an application. The virtual machines in a virtual appliance are preloaded with guest operating systems, and the applications they run are normally preconfigured and optimized to run in a virtual environment.
Since virtual machines are just a collection of files on a disk, they become portable. Virtual machines can be easily moved from one location to another by simply moving or copying the associated files. Using VMware vSphere features, such as vMotion, Enhanced vMotion, or Storage vMotion, virtual machines can be migrated from host to host or datastore to datastore while a virtual machine is running. Virtual machines can also be exported to an OVF or OVA to be imported into another VMware vSphere environment.