Help Center> Image Management Service> User Guide> Creating a Private Image> Creating a Linux System Disk Image from an External Image File> Preparing an Image File
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Preparing an Image File

You need to prepare an image file that meets the platform requirements and understand known issues of the OS (see Known Issues).

Table 1 Linux image file requirements

Image File Property

Requirement

OS
  • SUSE, Oracle Linux, Red Hat, Ubuntu, openSUSE, CentOS, Debian, Fedora, EulerOS, and NeoKylin
  • 32-bit or 64-bit
  • The OS cannot be bound to hardware.
  • The OS must support full virtualization.

For details about the supported OS versions, see Formats and OSs Supported for External Image Files. These OSs support automatic configuration. For details, see What Changes Will Be Made to an Image File Used for Registering a Private Image? For other OSs, check and install the VirtIO driver. On the image registration page, select Other Linux. 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

The image size cannot exceed 128 GB.

If the image size is between 128 GB and 1 TB, convert the image file into the RAW or ZVHD2 format and import the image through fast import.

Network

The following operation is mandatory. If the operation is not performed, the startup or network capability will be abnormal.

The following value-added operations are optional:

  • Enabling NIC multi-queue

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

  • Configuring dynamic assignment of IPv6 addresses

    IPv6 addresses are used to deal with the problem of IPv4 address exhaustion. In the image file, ECSs are configured to dynamically acquire IPv6 addresses. The created ECSs support both IPv4 and IPv6 addresses. For details, see How Do I Configure an ECS to Dynamically Acquire IPv6 Addresses?

Tool

You are advised to install Cloud-Init.

Cloud-Init is an open-source cloud initialization tool. When creating an ECS from an image with Cloud-Init, you can use the user data injection function to inject customized initialization information (for example, setting the ECS login password). You can also configure and manage a running ECS by querying and using metadata. If Cloud-Init is not installed, you cannot configure an ECS. As a result, you can only use the password in the image file to log in to the created ECSs.

For details, see Installing Cloud-Init.

Driver

Installing native Xen and KVM drivers

File system

Other requirements
  • Currently, images with data disks cannot be created. The image file must contain only the system disk, and the system disk size must be [40 GB, 1024 GB].
  • The initial password in the image file contains at least uppercase letters, lowercase letters, digits, and special characters (!@$%^-_=+[{}]:,./?).
  • In an image, the boot partition and system partition must be on the same disk.
  • 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. Otherwise, ECSs created from the registered image may not work properly.
  • The /etc/fstab file cannot contain automatic mounting information of non-system disks. Otherwise, the login to the created ECS may fail.
  • If the external image file uses the LVM as the system disk and the private image is registered from the external image file, ECSs created from the private image do not support file injection.
  • If the VM where the external image file is located has been shut down, it must be a graceful shutdown. Otherwise, a blue screen may occur when the ECS created from the private image is started.