A custom sysprep answer file is a file that stores a number of customization settings such as computer name, licensing information, and workgroup or domain settings. You can supply a custom sysprep answer file as an alternative to specifying many of the settings in the Guest Customization wizard.

Windows Server 2003, and Windows XP use a text file called sysprep.inf. Windows Server 2008, Windows Vista, and Windows 7 use an XML file called sysprep.xml. You can create these files using a text editor, or use the Microsoft Setup Manager utility to generate them. For more information about how to create a custom sysprep answer file, see the documentation for the relevant operating system.

You can prevent Windows from assigning new virtual machines or templates with the same Security IDs (SIDs) as the original virtual machine. 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.


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


  1. From the vSphere Web Client Home inventory page, select Policies and Profiles > Customization Specification Manager.
  2. Click the Create New Specification icon.
  3. In the Guest Customization wizard, select Windows from the Target Virtual Machine OS menu.
  4. (Optional) Select Use Custom Sysprep Answer File.
  5. Under Customization Specification Information, enter a name for the specification and an optional description and click Next.
  6. Select the option to import or create a sysprep answer file and click Next.



    Import a Sysprep answer file

    Click Browse and browse to the file.

    Create a Sysprep answer file

    Type the contents of the file in the text box.

  7. Select the type of network settings to apply to the guest operating system.



    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.

  8. To specify IPv4 related settings, select IPv4 and enter IP address and other network settings.
  9. To specify IPv6 related settings, select IPv6 to configure the virtual machine to use IPv6 network.
    1. Select Prompt user for an address when the specification is used. Selecting this option prompts you to enter IPv4 or IPv6 address.
    2. Select Use the following IPv6 addresses to choose an IPv6 address from the list.
      • Click the pencil icon to enter additional IPv6 addresses. You can specify the full address or shorten it by using zero compression and zero suppression. You should specify at least one IPv6 address. You can edit an existing address, but should not duplicate existing IPv6 addresses.

      • Enter subnet mask prefix. The prefix length should be between 1 to 128 where the default value is 64. Gateway is enabled by default, except when you choose Do not use IPv6.

  10. Select DNS and specify DNS server address and OK.
  11. Select WINS and specify primary and secondary WINS information.
  12. 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.

  13. 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.