Help Center/ Image Management Service/ User Guide/ Creating a Private Image/ Creating a Windows System Disk Image from an External Image File/ Preparing an Image File
Updated on 2024-10-25 GMT+08:00
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Preparing an Image File

You need to understand the constraints and known issues (see Known Issues) of your OS and prepare an image file that can be used to create a private image.

Currently, a large image file (maximum: 1 TB) can be imported only in RAW or ZVHD2 format. In addition to the requirements described in Table 2, a bitmap file needs to be generated alongside each RAW image file. The bitmap file is uploaded together with the image file. For details, see Fast Import of an Image File.

Initial Configuration for an Image File

The initial configuration must be completed on the source VM before an image file is exported from it. If you did not configure it, use the image file to create an ECS, configure the ECS, and use the ECS to create a private image. For details, see What Do I Do If a Windows Image File Is Not Pre-Configured When I Use It to Register a Private Image?

Table 1 Initial configuration for an image file

Configuration Item

How to Configure

Network

DHCP must be configured. Otherwise, the ECS startup or network capability will be abnormal. For details, see:

Configuring DHCP

The following operations are optional:

  • Enabling NIC multi-queue

    NIC multi-queue enables multiple vCPUs to process NIC interrupts, thereby improving network PPS and I/O performance. For details, see How Do I Enable NIC Multi-Queue for an Image?

  • Configuring dynamic assignment of IPv6 addresses

    IPv6 addresses are used to deal with IPv4 address exhaustion. If dynamic configuration is enabled in an image file, the ECSs created from this file will be automatically assigned an IPv6 address. These ECSs will support both IPv4 and IPv6 addresses. Configure dynamic assignment of IPv6 addresses. For details, see How Do I Configure an ECS to Dynamically Acquire IPv6 Addresses?

Tools

You are advised to install Cloudbase-Init.

Cloudbase-Init is an open-source tool for cloud instance initialization. When creating ECSs from an image with Cloudbase-Init, you can use user data injection to inject customized initialization details (for example, an ECS login password) to the ECSs. You can also configure and manage a running ECS by querying and using metadata. If Cloudbase-Init is not installed, you cannot apply custom configurations to the ECSs. You will have to use the original password in the image file to log in to the ECSs.

For details, see Installing and Configuring Cloudbase-Init.

If each of your ECSs requires a unique SID in a domain, run Sysprep after Cloudbase-Init is installed. For details, see Running Sysprep.

Plug-ins

You are advised to install the password reset plug-in CloudResetPwdAgent before creating a private image. In this way, you can reset the password of ECSs created from the image by a few clicks.

For details, see Installing the One-Click Password Reset Plug-In.

Drivers

An ECS can run properly only after Xen Guest OS drivers (PV drivers) and KVM Guest OS drivers (VirtIO drivers) are installed on it. To ensure that ECSs support both Xen and KVM and to improve network performance, PV and VirtIO drivers must be installed for the image.

Image File Properties

Table 2 Windows image file properties

Image File Property

Requirement

OS
  • Windows Server 2008, Windows Server 2012, Windows Server 2016, Windows Server 2019, Windows 10
  • 32-bit or 64-bit
  • The OS cannot be bound to specific hardware.
  • The OS must support full virtualization.

For details about the supported OS versions, see External Image File Formats and Supported OSs. These OSs support automatic configuration. For details, see What Will the System Do to an Image File When I Use the File to Register a Private Image? For other OSs, check and install Guest OS drivers. On the image registration page, select Other Windows. After the image is imported, whether the system is started depends on the driver integrity.

Image format

VMDK, VHD, QCOW2, RAW, VHDX, QED, VDI, QCOW, ZVHD2, and ZVHD

Image size

If an image is no larger than 128 GB, import it directly.

If an image is between 128 GB and 1 TB, convert the image file into RAW or ZVHD2 and import it using fast import.

Other

  • Currently, images with data disks cannot be created. The image file must contain only a system disk, and the system disk size must be [40 GB, 1024 GB].
  • The initial password in the image file must contain uppercase letters, lowercase letters, digits, and special characters (!@$%^-_=+[{}]:,./?).
  • The boot partition and system partition must be on the same disk.
  • For an external image file, you need a tenant administrator account and password combination.
  • If you use an external image file to create a Windows system disk image and then use the image to create an ECS, you cannot log in to the ECS using a key pair or obtain the password from the key pair.
  • Supported boot modes:

    Some x86 OS images support the UEFI boot mode. (For details, see OSs Supporting UEFI Boot Mode.)

    Arm OS images support only the UEFI boot mode.

  • The image file cannot be encrypted, or ECSs created from the registered image may not work properly.
  • A VMDK image file must be generated from a VM created in VMware Tools. Otherwise, the system may fail to start due to image parsing problems.