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Last updated: Apr 15, 2024

What Is the VMX File in VMware?

The VMX file is a core component in VMware's ESXi, an enterprise-class, type-1 hypervisor developed by VMware for deploying and serving virtual computers. As the backbone of VMware's virtualization platform, understanding the VMX file's role, structure, and functionality is crucial for IT professionals who manage and configure virtual machines (VMs) within a virtualized infrastructure.

In this article, we delve into the VMX file, exploring its significance in the VMware ESXi environment. We'll start by defining what the VMX file is, highlighting its position as the primary configuration file for a VM. Each VMX file contains a plain-text inventory of settings, including hardware specifications, resource allocations, and operational parameters that dictate how the VM operates within the ESXi host.

Furthermore, we will guide you through the anatomy of a VMX file, breaking down its key components and how they interact to bring a virtual machine to life. From specifying the virtual hardware version to defining the network adapters, every line in a VMX file plays a vital role in the VM's performance and behavior.

What is a VMX file?

A VMX file is a configuration file used by VMware virtualization software, specifically within environments like VMware Workstation and VMware ESXi. It serves as the primary configuration file for a virtual machine (VM) created on these platforms. The VMX file is written in plain text and contains a series of key-value pairs that define the settings and specifications of a virtual machine. These settings include a wide array of parameters such as the VM's hardware compatibility, allocated resources (like CPU, memory, and disk space), network configurations, and other operational parameters that determine how the VM operates and interacts with the physical host and other virtual machines.

The structure of a VMX file allows it to be easily edited with a text editor, enabling administrators and users to manually adjust the VM's configurations as needed. This flexibility is crucial for tasks like troubleshooting, performance tuning, or making adjustments to the VM's hardware setup without using the graphical interface of VMware's management tools.

Each virtual machine has its own VMX file, which is created when the VM is initially set up. The file resides on the datastore that hosts the VM's files, making it accessible for backup, manual editing, or migration purposes. Understanding and manipulating the VMX file can be an essential skill for IT professionals working in environments that utilize VMware's virtualization technology, allowing for precise control over the virtual machine's behavior and resources.

What is the VMX Format?

The VMX file format is essentially a plain-text file that uses a simple key-value pair structure to define the configuration of a virtual machine (VM) within VMware environments, such as VMware Workstation, VMware Player, and VMware ESXi. This format is designed to be both human-readable and easily editable, facilitating manual adjustments by administrators and users.

Each line in a VMX file specifies a particular setting for the VM, using the format parameterName = "value". These parameters cover a broad range of VM attributes, including but not limited to, hardware specifications (like CPU and memory allocation), network settings, security options, and behavior controls for the VM's virtual BIOS or UEFI. The flexibility of the VMX format allows for detailed customization of the VM's operational environment, enabling it to cater to specific workload requirements or performance optimizations.

VMX File Example

Here is a simplified example of what contents in a VMX file might look like:

.encoding = "UTF-8"
displayName = "ExampleVM"
guestOS = "windows8-64"
memsize = "4096"
scsi0:0.fileName = "ExampleVM.vmdk"
ethernet0.networkName = "VM Network"
ethernet0.connectionType = "bridged"
mks.enable3d = "TRUE"

  • .encoding specifies the encoding used in the VMX file.
  • displayName is the name of the VM as it appears in VMware products.
  • guestOS specifies the operating system installed on the VM.
  • memsize sets the amount of memory allocated to the VM in MB.
  • scsi0:0.fileName refers to the path of the primary virtual disk file.
  • ethernet0.networkName and ethernet0.connectionType define the network adapter's configuration.
  • mks.enable3d determines whether 3D graphics acceleration is enabled.

Programs that Open VMX Files

VMX files are primarily associated with VMware's range of virtualization products. Here are some of the key programs capable of opening and working with VMX files:

  • VMware Workstation: A full-featured desktop virtualization software that allows users to manage and run VMs on a single physical machine.
  • VMware ESXi: An enterprise-class, type-1 hypervisor designed for deploying and serving virtual computers as part of VMware's vSphere suite.
  • VMware Fusion: Provides similar functionality to VMware Workstation but is designed for macOS, allowing users to run Windows and other operating systems as VMs on a Mac.
  • VMware Player: A free software that enables users to easily run existing virtual appliances and create its own virtual machines (limitations apply compared to Workstation).

In addition to VMware's proprietary tools, text editors (like Notepad++ on Windows, TextEdit on macOS, or gedit on Linux) can also open VMX files for viewing or editing, given the file's plain-text nature. However, making changes directly to VMX files should be done with caution and typically only by those who are knowledgeable about VMware products and virtual machine configuration parameters.

How to open VMX file?

Opening a VMX file can be approached in two main ways: through VMware software for managing and running virtual machines, or using a text editor for viewing or editing the file's contents. Here’s how to do both:

Using VMware Software

To open and run a VMX file using VMware software (such as VMware Workstation, VMware Fusion, or VMware Player), follow these steps:

  • Launch the VMware application: Open your VMware software of choice.
  • Open a Virtual Machine: Look for an option to open a virtual machine. This could be under a menu item such as File > Open... or a similar command.
  • Navigate to the VMX File: Use the file dialog to navigate to the location of the VMX file you wish to open.
  • Select the VMX File: Click on the VMX file to select it, then click Open or OK to proceed.
  • Run the Virtual Machine: With the VM loaded, you can now start the virtual machine using the software's controls, typically a Start or Power On button.

Using a Text Editor

To view or edit the contents of a VMX file with a text editor, follow these instructions:

  1. 1. Choose a Text Editor: Select a text editor of your choice (e.g., Notepad++ on Windows, TextEdit on macOS, or gedit on Linux).
  2. 2. Open the Text Editor: Launch the text editor application.
  3. 3. Open the VMX File:
    • In the text editor, go to File > Open... or a similar command.
    • Navigate to the directory containing the VMX file.
    • Select the VMX file and click Open or a similar button.
  4. 4. View or Edit the VMX File: You can now read and make changes to the VMX file as needed. Be cautious when editing, as incorrect settings can affect the virtual machine's operation.

Note on Editing VMX Files

While editing a VMX file in a text editor is straightforward, it’s important to exercise caution. Incorrect entries or changes can cause the virtual machine to malfunction or fail to start. Always ensure you have a backup of the original VMX file before making any modifications. If you’re unsure about a setting, consult the VMware documentation or seek advice from a knowledgeable source.

How to use VMX file?

Using a VMX file effectively revolves around managing and configuring VMware virtual machines. The VMX file is at the heart of a virtual machine's configuration, dictating its hardware, resources, and behavior within VMware environments such as VMware Workstation, VMware Fusion, VMware Player, and VMware ESXi. Here's a breakdown of how to use a VMX file across various scenarios:

1. Creating a New Virtual Machine

When you create a new virtual machine using VMware software, the process automatically generates a VMX file based on the configurations you specify. This includes the operating system, allocated memory, CPU cores, network settings, and more. The VMX file is saved in the same directory as the virtual machine's other files (like virtual disks).

2. Editing VMX Files for Custom Configuration

To customize or tweak advanced settings of a virtual machine that aren't available in the VMware graphical user interface, you can directly edit the VMX file:

  1. 1. Shut down the virtual machine: Ensure the VM is not running to avoid conflicts.
  2. 2. Back up the VMX file: Before making changes, copy the existing VMX file as a backup.
  3. 3. Edit the VMX file: Open the VMX file in a text editor. Make the desired changes to the configuration parameters. For example, you might add or modify lines to adjust memory allocation, enable/disable features, or set advanced hardware compatibility options.
  4. 4. Save the changes: After editing, save the file and close the text editor.
  5. 5. Reload the VM: Start the VMware software and load the virtual machine. VMware will read the updated VMX file and apply the new configurations.

3. Transferring Virtual Machines

The VMX file is essential when transferring a virtual machine from one host system to another:

  1. 1. Copy VM files: Transfer the entire folder containing the VMX file and associated virtual disks to the new host.
  2. 2. Register the VM: On the new host, use VMware's interface to open the VMX file, effectively registering the virtual machine in the VMware software.
  3. 3. Power on the VM: The VM should now be ready to start on the new host, with all its configurations preserved.

4. Troubleshooting and Advanced Configuration

VMX files can be invaluable for troubleshooting issues with virtual machines or for enabling advanced features not exposed through the GUI. For instance, you might edit a VMX file to:

  • Enable debugging or logging features for troubleshooting.
  • Configure advanced networking or storage options.
  • Adjust resource allocations beyond typical limits.

5. Using VMX Files in Automation Scripts

For environments with extensive virtualization infrastructure, VMX files can be manipulated programmatically:

  • Scripts can be written to modify VMX files in bulk, applying specific configurations across multiple VMs.
  • Automation tools can use VMX files to deploy, configure, or manage VM lifecycles efficiently.

Best Practices

  • Documentation: Always refer to VMware's official documentation for the specific syntax and supported parameters when editing VMX files.
  • Version Control: Consider using version control for VMX files if you frequently make changes. This practice can help track changes and revert to previous versions if needed.
  • Security: Be aware of the security implications of certain VMX file settings, especially those related to network configuration and resource access.

What is the difference between a VMDK and a VMX file in VMware ESXi?

In VMware ESXi, as well as other VMware virtualization platforms, VMX and VMDK files are fundamental components of virtual machine architecture, but they serve very different purposes. Understanding the difference between these two file types is essential for managing and configuring VMs effectively.

VMX File

  • Definition: A VMX file is a configuration file for a VMware virtual machine. It is a plain-text file that contains key-value pairs, defining the settings and specifications of a virtual machine.
  • Contents: The VMX file includes configurations such as the VM's name, the operating system installed, hardware specifications (e.g., CPU, memory, network adapters), and other operational parameters that determine how the VM interacts with the physical host and other VMs.
  • Purpose: Its primary purpose is to store the configuration information of the VM. When you start a virtual machine, the VMware ESXi hypervisor reads the VMX file to determine how to allocate resources to the VM.


  • Definition: A VMDK (Virtual Machine Disk) file is a virtual disk file that stores the contents of the virtual machine's hard disk drive. It can contain an operating system, applications, and data associated with the VM.
  • Contents: The VMDK file acts as a physical hard drive for the VM. It can be split into multiple files for easier management and can also be compressed to save space.
  • Purpose: Its main purpose is to simulate a physical disk drive for the virtual machine. It provides the storage necessary for the VM to operate, including the installation files for the operating system, applications, and personal data stored within the VM.

Key Differences

  • Functionality: The VMX file defines the configuration and operational parameters of a virtual machine, such as hardware settings and how the VM should boot, while the VMDK file represents the actual virtual hard disk where the VM's data is stored.
  • Content: VMX files are text-based and can be edited with a simple text editor to change the VM's configuration. VMDK files are binary files that contain the actual data of a VM's hard drive.
  • Interdependence: While both files are crucial for a VM's operation, they serve different aspects of the VM's functionality. The VMX file is necessary to start and configure the VM, whereas the VMDK file is needed for the VM's storage requirements.

How to recover VMware files if they are lost?

Recovering lost VMware files, such as VMX and VMDK files, can be critical for restoring virtual machines and their associated data. DiskInternals VMFS Recovery is a tool designed for this purpose, providing a way to recover files from VMFS (Virtual Machine File System) partitions used by VMware ESXi and other VMware products. Here's a step-by-step guide on using VMware data recovery software for recovering lost VMware files:

Step 1: Install DiskInternals VMFS Recovery

  • Download DiskInternals VMFS Recovery from the official DiskInternals website.
  • Install the software on a Windows computer. It's recommended to install it on a machine that is not the one hosting the lost files, to avoid potential data overwrite issues.

Step 2: Connect to the VMware ESXi Server

  • Launch DiskInternals VMFS Recovery.
  • If the VMware disks are locally connected to your computer, the software should detect them automatically. If the disks are on a remote ESXi server, you'll need to connect to the server. You can do this within the software by providing the server's IP address and your login credentials.

Step 3: Scan for Lost Files

  • Once the drives are accessible, navigate to the VMFS volume where the lost files were located.
  • Right-click on the volume and select "Scan" to start the scanning process. This may take some time, depending on the size of the volume and the amount of data.

Step 4: Preview and Recover Files

  • After the scan completes, the software will display a list of recoverable files.
  • Navigate through the files and locate the VMX, VMDK, or any other VMware-related files you wish to recover. DiskInternals VMFS Recovery allows you to preview some types of files before recovery, which can help verify their integrity and content.
  • Select the files you want to recover and choose a location to save them. It's crucial to save recovered files to a different disk than the one they were recovered from to prevent data overwrite.

Step 5: Restore the Recovered Files to Your VMware Environment

  • Once the files are recovered, you can transfer them back to your VMware ESXi server or wherever they are needed.
  • If recovering a VMX file, you may be able to simply add it back to your VMware inventory and start the virtual machine.
  • If recovering a VMDK file, you might need to create a new VM and attach the VMDK as its hard disk.

Tips and Considerations

  • Backup Regularly: Regular backups of your VMware environments can significantly reduce the need for data recovery efforts.
  • Handle with Care: Data recovery processes should be handled with care. Mistakes during the recovery process can lead to permanent data loss.
  • Professional Assistance: If you're not confident in performing the recovery yourself or if the data is particularly critical, consider seeking professional data recovery services.

DiskInternals VMFS Recovery is a powerful tool for recovering lost VMware files, but success can vary based on the specific circumstances of the data loss. Always proceed with caution and prioritize the safety of your data throughout the recovery process.

Tip: learn more on how to recover VMware virtual machine.


In the realm of VMware ESXi and virtualization, understanding the intricacies of key file types such as VMX and VMDK files is paramount for effective virtual machine management. The VMX file acts as the blueprint of a virtual machine, detailing its configuration, hardware specifications, and operational parameters, ensuring that the virtual machine boots and runs according to the specified settings. On the other hand, the VMDK file represents the virtual machine's hard drive, housing the operating system, applications, and data, and playing a critical role in the VM's storage capability.

The distinction between these files underpins their importance in a VMware environment, highlighting the need for careful management, backup, and recovery strategies. In scenarios where these vital files are lost or corrupted, tools like DiskInternals VMFS Recovery offer a lifeline, enabling the recovery of lost data from VMFS partitions. This process, while technical, is essential for maintaining the continuity and integrity of virtualized environments, ensuring that virtual machines can be restored and operational with minimal downtime.

Recovery efforts, while often successful, underscore the importance of preventative measures such as regular backups and meticulous configuration management. As the backbone of virtual machine functionality, the careful handling of VMX and VMDK files cannot be overstated. By understanding their roles, managing their configurations, and being prepared for recovery scenarios, IT professionals can ensure the resilience and efficiency of their VMware virtual environments.


  • What is the difference between VMDK and VMEM?

    Each VMDK file serves as either a virtual machine's disk drive or as a delta file, which stores changes made since the last snapshot was taken. The VMEM file, on the other hand, captures the contents of the virtual machine's memory. Typically, this file vanishes when you power off your VM, except in cases where the machine has encountered a crash.

  • What is the purpose of VMX file?

    The VMXF file contains extra configuration details for virtual machines organized into teams, facilitating easier management. When virtual machines are grouped in this manner, it enhances administrative efficiency. Should a virtual machine be detached from its team, its associated VMXF file will persist.

  • What is the meaning of VMX?

    Virtual Machine Extensions refer to x86 virtualization instructions on processors. AltiVec, known as VMX by IBM, is a SIMD instruction set for floating-point and integer operations. The vMX 3D represents an Ethernet router within Juniper Networks' MX-Series. The file extension .vmx is associated with VMware's virtual machine configuration files.

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