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 starts the first time after customization.


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


  1. Select Menu > Policies and Profiles and click Customization Specification.
  2. Click the Create a new specification icon.
    The New Customization Specification wizard opens.
  3. On the Specify Properties page, select Windows as a target guest operating system.
  4. Enter a name and description for the customization specifications and click Next.
  5. On the Set Registration Information page, enter the virtual machine owner’s name and organization and click Next.
  6. On the Computer name page, enter a computer name for the guest operating system and a domain name.
    The operating system uses the computer name to identify itself on the network. On Linux systems, it is called the host name.
    Option Action
    Use the virtual machine name Select to 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 63 characters, it is truncated.
    Enter a name in the Clone/Deploy wizard Select to be prompted to enter a name during cloning or deployment.
    Enter a name
    1. Enter a name.

      The name can contain alphanumeric characters and a hyphen (-). It cannot contain a period (.), blank spaces, or special characters, and cannot contain digits only. Names are not case-sensitive.

    2. (Optional) To ensure that the name is unique, select the Append a numeric value check box.

      This action appends a hyphen followed by a numeric value to the virtual machine name. The name is truncated if it exceeds 63 characters when combined with the numeric value.

    Generate a name using the custom application configured with vCenter Server Optional: Enter a parameter that can be passed to the custom application.
  7. On the Enter Windows License page, provide licensing information for the Windows operating system and click Next.
    Option Action
    For nonserver operating systems Enter the Windows product key for the new guest operating system.
    For server operating systems
    1. Enter 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. If you select Per server, enter the maximum number of simultaneous connections for the server to accept.
  8. On the Set Administrator Password page, configure the administrator password for the virtual machine and click Next.
    1. Enter 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) Select the Automatically logon as Administrator check box to log users in to the guest operating system as Administrator, and select the number of times to log in automatically.
  9. On the Time zone page, 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 in to the guest operating system and click Next.
    See the Microsoft Sysprep documentation for information about RunOnce commands.
  11. On the Configure Network page, select the type of network settings to apply to the guest operating system.
    Option Action
    Standard settings

    Select Use standard network settings and click Next.

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

    Custom settings
    1. Select Manually select custom settings.
    2. Select a network adapter from the list or add a new one.
    3. For the selected network interface in the virtual machine, click the pencil icon.

      The Edit Network dialog box opens.

    4. In the Edit Network dialog box, configure the network settings for the selected network interface.
    5. Click OK to save your configuration and close the Edit Network dialog box.
  12. To specify IPv4 related settings, select IPv4 and enter an IP address and other network settings.
  13. To specify IPv6 related settings and to configure the virtual machine to use an IPv6 network, select IPv6 .
    1. Select Prompt user for an address when the specification is used.
      Selecting this option prompts you to enter IPv6 address.
    2. To choose an IPv6 address from the list, select Use the following IPv6 addresses .
      • To enter additional IPv6 address, click the Add a new adapter icon.

        You can specify the full address or shorten it by using zero compression and zero suppression. You must specify at least one IPv6 address. You can edit an existing address, but you must not duplicate existing IPv6 addresses.

      • Enter subnet mask prefix.

        The prefix length must be between 1 and 128 where the default value is 64. Gateway is enabled by default, except when you select Do not use IPv6.

  14. Select DNS, specify the DNS server address, and click OK.
  15. Select WINS and specify the primary and secondary WINS information.
  16. On the Set Workgroup or Domain page, select how the virtual machine participates in the network and click Next.
    Option Action
    Workgroup Enter a workgroup name. For example, MSHOME.
    Windows Server Domain
    1. Enter the domain name.
    2. To add a computer to the specified domain, enter the user name and password for a user account that has permission.
  17. (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.

  18. 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.