Use the Guest Customization wizard to save Windows guest operating system settings in a specification that you can apply when cloning virtual machines or deploying from templates.

Note: The default administrator password is not preserved for Windows Server 2008 after customization. During customization, the Windows Sysprep utility deletes and recreates the administrator account on Windows Server 2008. You must reset the administrator password when the virtual machine boots the first time after customization.


Ensure that all requirements for customization are met. See Guest Operating System Customization Requirements.


  1. From the vSphere Client Home page, select Customization Specifications Manager.
  2. Click the Create New Specification icon.
  3. In the Guest Customization wizard, select Windows from the Target Virtual Machine OS menu.
  4. Under Customization Specification Information, enter a name for the specification and an optional description and click Next.
  5. Type the virtual machine owner’s name and organization and click Next.
  6. Enter the guest operating system's computer name and click Next.
    The operating system uses this name to identify itself on the network. On Linux systems, it is called the host name.
    Option Action
    Enter a name
    1. Type a name.

      The name can contain alphanumeric characters and the hyphen (-) character. It cannot contain periods (.) or blank spaces and cannot be made up of digits only. Names are not case-sensitive.

    2. (Optional) To ensure that the name is unique, select Append a numeric value to ensure uniqueness. This appends a hyphen followed by a numeric value to the virtual machine name. The name is truncated if it exceeds 15 characters when combined with the numeric value.
    Use the virtual machine name The computer name that vCenter Server creates is identical to the name of the virtual machine on which the guest operating system is running. If the name exceeds 15 characters, it is truncated.
    Enter a name in the Deploy wizard The vSphere Web Client prompts you to enter a name after the cloning or deployment is complete.
    Generate a name using the custom application configured with vCenter Server Enter a parameter that can be passed to the custom application.
  7. Provide licensing information for the Windows operating system and click Next.
    Option Action
    For non-server operating systems Type the Windows product key for the new guest operating system.
    For server operating systems
    1. Type the Windows product key for the new guest operating system.
    2. Select Include Server License Information.
    3. Select either Per seat or Per server.
    4. (Optional) If you select Per server, enter the maximum number of simultaneous connections for the server to accept.
  8. Configure the administrator password for the virtual machine and click Next.
    1. Type a password for the administrator account and confirm the password by typing it again.
      Note: You can change the administrator password only if the administrator password on the source Windows virtual machine is blank. If the source Windows virtual machine or template already has a password, the administrator password does not change.
    2. (Optional) To log users into the guest operating system as Administrator, select the check box, and select the number of times to log in automatically.
  9. Select the time zone for the virtual machine and click Next.
  10. (Optional) On the Run Once page, specify commands to run the first time a user logs into the guest operating system and click Next.
    See the Microsoft Sysprep documentation for information about RunOnce commands.
  11. Select the type of network settings to apply to the guest operating system.
    Option Action
    Typical settings

    Select Typical settings and click Next.

    vCenter Server configures all network interfaces from a DHCP server using default settings.

    Custom settings
    1. Select Custom settings and click Next.
    2. For each network interface in the virtual machine, click the ellipsis button (...) .
    3. Enter IP address and other network settings and click OK.
    4. When all network interfaces are configured, click Next.
  12. Select how the virtual machine will participate in the network and click Next.
    Option Action
    Workgroup Type a workgroup name. For example, MSHOME.
    Windows Server Domain
    1. Type the domain name.
    2. Type the user name and password for a user account that has permission to add a computer to the specified domain.
  13. (Optional) Select Generate New Security ID (SID) and click Next.
    A Windows Security ID (SID) is used in some Windows operating systems to uniquely identify systems and users. If you do not select this option, the new virtual machine has the same SID as the virtual machine or template from which it was cloned or deployed.

    Duplicate SIDs do not cause problems when the computers are part of a domain and only domain user accounts are used. However, if the computers are part of a Workgroup or local user accounts are used, duplicate SIDs can compromise file access controls. For more information, see the documentation for your Microsoft Windows operating system.

  14. Click Finish to save your changes.


The customization specification that you created is listed in the Customization Specification Manager. You can use the specification to customize virtual machine guest operating systems.