VMware Player online course

What Is a Guest Operating System in VMware Player?

Learn what a guest operating system is, how it differs from the host OS, how virtual machines use ISO files, and how to install a guest OS in VMware Player.

A guest operating system is an operating system installed and running inside a virtual machine (VM). The VM is a software-defined computer environment that provides virtual processors, memory, storage, and other devices for the guest operating system.

For example, a physical computer running Windows 7 can use VMware Player to create a virtual machine and run Damn Small Linux inside it. Windows 7 remains the computer's main operating system, while Damn Small Linux is the guest operating system.

VMware Player is a desktop virtualization application used to create and run virtual machines. It allows a guest OS to run alongside the host OS without replacing it or requiring a separate physical computer.

Guest Operating System, Host Operating System, and Virtual Machine

What is a host operating system?

The host operating system is the operating system installed directly on the physical computer. It controls the computer's actual hardware and runs normal applications, including VMware Player.

The guest operating system is installed inside a virtual machine. It interacts with virtual hardware presented by VMware Player rather than directly controlling the physical computer's hardware.

What is a virtual machine?

A virtual machine is a software-based computer. VMware Player allocates part of the physical computer's resources to the VM and presents those resources as virtual hardware. The VM acts as the container, or emulated computer environment, in which the guest OS is installed.

Creating a VM and installing an operating system in that VM are related but separate steps. First, you create and configure the virtual hardware. Next, you attach installation media and install the guest OS onto the VM's virtual disk.

The layered relationship

The simplified arrangement is:

Physical hardware
    └── Host operating system
          └── VMware Player
                └── Virtual machine and its virtual hardware
                      └── Guest operating system

The host and guest do not have to be the same operating system. A Windows host can run a Linux guest, and a supported Windows host can run another Windows guest, for example.

Example: Linux on a Windows Computer

Suppose the physical computer runs Windows 7. Windows 7 is the host OS. After VMware Player creates a virtual machine, you install Damn Small Linux in that VM. Damn Small Linux is the guest OS.

• Windows 7 continues to run the physical computer.
• VMware Player runs as an application on Windows 7.
• The virtual machine receives assigned virtual hardware.
• Damn Small Linux runs inside that virtual machine.

The guest OS is independent from the host in several important ways: it has its own virtual disk, its own operating-system files, and its own applications. However, it still depends on the host for access to physical resources such as processor time, memory, storage, and networking.

Examples of Guest Operating Systems

VMware Player can run many kinds of guest operating systems, depending on the VMware version, the host platform, and the virtual hardware configuration.

Guest Operating System Compatibility

Guest OS compatibility means whether a particular guest operating system is supported or expected to work with a specific VMware product version and virtual hardware configuration.

VMware Player supports many guest operating systems, but support is not universal. Compatibility can vary according to:

• The VMware Player or VMware Workstation version.
• The host operating system and physical hardware.
• The guest OS version and architecture, such as 32-bit or 64-bit where applicable.
• The VM's virtual hardware version.
• Available memory, processor features, disk space, and device settings.

An operating system may be technically capable of starting in a VM without being officially supported by the virtualization product. These are different claims: potentially runs does not necessarily mean officially supported.

Before creating the VM, verify the intended guest OS in the applicable VMware Workstation guest operating system compatibility documentation when a separate Player-specific listing is not provided. If the exact OS is not listed, use a general or closely related guest profile only when the documentation indicates that this is appropriate.

During VM creation, VMware Player asks you to select the intended guest operating system type and version. This selection helps VMware choose suitable default virtual hardware and settings; it does not itself install the operating system.

Changing the guest operating system version may be necessary if the VM was created with an incorrect profile.

Installation Media for a Guest Operating System

Installing an operating system in a VM requires legitimate installation media, just as installing an OS on a physical computer does. The media must match the intended guest operating system and, where applicable, its processor architecture.

Common installation-media options are an installer disc and an ISO image file.

What is an ISO image?

An ISO image, also called an ISO file, is a single file that represents the contents and structure of a disc. Operating-system publishers commonly distribute installers as ISO files because one downloadable file can contain the complete bootable installation media.

An ISO is not normally installed by opening it as an ordinary document. VMware Player connects it to the VM's virtual CD/DVD drive, a virtual device that can use either a physical disc or an ISO file. When the VM starts, it can boot from that device and launch the operating-system installer.

How a Guest OS Is Installed in VMware Player

1. Obtain legitimate installation media for the desired operating system, such as an installer disc or a suitable ISO image.
2. Create a virtual machine and select the intended guest OS type and version when prompted.
3. Configure the VM's virtual hardware. Assign adequate memory, processor resources, virtual disk space, and other required devices while leaving enough resources for the host OS.
4. Configure the VM's CD/DVD device to use the ISO image file or the physical optical drive.
5. Start the VM. If the VM boots from the attached media, the guest OS installer appears.
6. Follow the guest operating system's installation instructions and install it onto the VM's virtual hard disk.
7. After installation, disconnect the installation media if the VM repeatedly starts the installer instead of the installed system.

For a downloaded Linux installer, the typical sequence is:

Create VM → Attach Linux ISO → Start VM → Boot from virtual CD/DVD → Install Linux to virtual disk

For a physical installer disc:

Insert disc in host → Configure VM CD/DVD device → Start VM → Boot from physical disc → Install guest OS

See manually installing a guest operating system for a workflow focused on supplying installation media yourself. A VM can also use a virtual CD/DVD device configured through the VM settings; related device configuration is described in adding a CD-ROM drive.

Resources and Virtual Hardware

The guest OS uses resources assigned by the VM. These resources are virtual from the guest's point of view, but they ultimately come from the physical host.

• Memory: RAM assigned to the VM while it is running.
• Processors: Virtual processor cores scheduled on the host's physical processor.
• Storage: One or more virtual hard disks stored as files on the host.
• CD/DVD: A virtual drive connected to an ISO or physical disc.
• Networking: A virtual network adapter connected through a selected VMware networking mode.

Assigning too few resources can make the guest slow or prevent installation. Assigning too many can make the host slow or unstable. Resource requirements come from the guest OS and its applications, so check those requirements before configuring the VM.

For related configuration, see changing memory allocation, configuring a virtual hard disk, and networking configurations.

Troubleshooting Guest OS Installation

The VM does not start the operating-system installer

Possible causes include:

• No installer disc or ISO is connected.
• The ISO path is incorrect, or the file is unavailable.
• The VM is not configured to boot from its virtual CD/DVD device.

Check the VM's CD/DVD settings, reconnect valid installation media, and verify the boot-device configuration. Confirm that the ISO is a complete, bootable installer image rather than an incomplete download.

The intended guest OS is not listed

The available VMware Player version may not explicitly identify that operating system. Alternatively, the product may expect a general or closely related guest OS profile.

Consult the applicable guest OS compatibility documentation and choose the nearest appropriate supported profile only when the documentation recommends it. Selecting a profile is not a substitute for confirming actual compatibility.

The guest OS runs poorly or cannot install

Check the following:

• The VM has enough assigned memory, disk space, and processor resources.
• The guest OS version and architecture are compatible with the VMware product and virtual hardware.
• The installation media is complete and undamaged.
• The host still has enough free memory and processing capacity.

Validate the installer media, confirm compatibility, and adjust VM resources without starving the host operating system.

Key Points to Remember