Overview of Mirroring

What mirroring is

An image is a cloud or bare metal server template that contains the software and the necessary configuration. It contains the operating system or business data. It can also contain application software (e.g., database software) and proprietary software. There are public images, private images, shared images, and marketplace images. The public image is the operating system image provided by the system by default; Private image is the image created by users based on the ECS instance they are using. Shared images are private images that are shared to you by other users; Marketplace images are images provided by third-party service providers, including pre-installed operating systems, application environments, and various software.

Image Management Service provides a simple and convenient self-management function of images. Users can apply for cloud server using public image, private image or shared image flexibly and conveniently. At the same time, users can also create private images through existing cloud servers or use external image files to realize business migration to the cloud or cloud migration.

What is the difference between backup, snapshot and image?

Public Image

A public image is an image that contains the common standard operating system, visible to all users, including the operating system and pre-installed public applications. It supports mainstream operating systems such as Ubuntu, CentOS, Debian, etc. Users can select or create private images from a rich public image library, so as to quickly create or batch copy elastic cloud servers. Please self-configure the application environment or related software according to your actual situation.

For more information on public images, see "Overview of Public Images".

Private Mirroring

Private images contain images of operating system or business data, pre-installed public apps, and the user's private apps, visible only to the user personally.

Types of images	Instructions
System disk image	Contains the image of the operating system and application software required by the user to run the business. The system disk image can be used to create a cloud server and migrate user business to the cloud.
Data disk image	A mirror containing only the user's business data. A data image can be used to create a cloud hard drive to migrate a user's business data to the cloud.
Whole machine mirror	Also known as the full image, it contains the image of the operating system, application software and business data required by the user to run the business. The whole machine image contains the system disk and all the data disks mounted on it. The whole machine image is made based on the difference backup, which is more efficient than the system disk image and the data disk image with the same disk capacity.
ISO image	Register the ISO file of the external image to the private image of the cloud platform. ISO images are special images that can only be issued as a temporary transitional cloud server.

How to choose an image

When creating an instance of ECS, you must choose a mirror. The mirror selection needs to consider the following factors:

Table 2 Influencing factors of mirror selection

Influencing factors	Instructions
Zones and availability zones	An image is a regional resource, and you cannot use an image to create an instance across regions. For example, when you create an instance in region A, you can only select the mirror located in region A. For more information about zones, see Zones and Availability Zones. To create an instance with an image from another region, you can first copy the image to the current region, see Copying Images Across Regions for details.
Type of mirror	There is a simple rule of judgment when it comes to actually choosing the mirror type: • If you need a clean version of OS, choose a public image. • If you want to replicate a new instance based on your current cloud server instance, choose a private image. • If you want to use an image shared by someone else, select Shared Image. • If you need a full software environment, such as the Magento e-commerce system, choose the Marketplace mirror.
Operating system	Refer to Elastic cloud server type and supported operating system versions to choose the right operating system for your business requirements.
Mirroring Fees	Using mirrors, there may be a fee. See billing standards for mirrors for details.
Built-in software	The running environment or application software of the instance is pre-installed in the market image, and you can choose the corresponding image to create the instance according to your needs. For more information, see the Marketplace Mirror Class.

Guidelines for Using Mirror

Operation Instructions	Relevant documentation	Relevant documentation
Creating Mirrors	If you need an image of a designated elastic cloud server, create a private image using the designated elastic cloud server in advance.	Creating an image
Import the image	If you need to use a local image file, import the image file in advance and register it as a private image of the cloud platform.	Create a private image through the image file  Formats and operating system types supported by external image files
Copying the image	• If you need to use a private image in another region, you can do so with the cross-region copy image feature. • If you need to convert an encrypted image to an unencrypted image, you can do so through the intra-zone copy image function. • If you need to create a shared image as a private image, you can do so through the Copy Shared Image feature.	• Copy the image across regions • Copy the mirror within the region • Copy shared image
Export image	After creating a private image, you can export the image to the OBS standard bucket and download it for local use.	Exporting the image
Modify the mirror	To facilitate the management of private images, you can modify the information of private images such as name, description, memory, and how the image is started as needed.	Modifying the image properties
Deleting an image	A private image can be deleted when you no longer need it.	Deleting an image