# Overview

#### What Is an Image?

An image is a template of the BMS running environment. It contains an OS and runtime environment, and some pre-installed applications. An image file is equivalent to a copy file that contains all data in the system disk.

#### Image Types

Images can be classified into public images, private images, and shared images.

Table 1 Image types
Image Type | Description
--- | ---
Public image | A public image is provided by the cloud platform and is available to all users. It contains an OS and preinstalled public applications.
Private image | A private image is created by a user and is available only to the user who created it. It contains an OS, pre-installed public applications, and the user's private applications. Using a private image to create BMSs frees you from repeatedly configuring BMSs.
Shared image | A shared image is a private image other users share with you.

#### Public Images

Public images are provided by the system. These images are available to all users, compatible with BMSs and most mainstream OSs, and are pre-installed with necessary plug-ins. Public images available to you vary depending on the BMS flavor you selected. For details, see OSs Supported by Different Types of BMSs.

Characteristics

- OS types: Linux and Windows OSs that are updated and maintained periodically
- Pre-installed software: plug-ins that BMS storage, networks, and basic functions depend on

  These plug-ins are necessary for BMSs to run properly. Do not delete or modify any of them. Otherwise, basic BMS functions will be affected.

  Table 2 Pre-installed software
  Software | Description
  --- | ---
  Cloud-Init | Cloud-Init is an open-source cloud initialization program, which initializes specific configurations, such as the host name, key, and user data, of a newly created BMS.
  bms-network-config | This plug-in is used to automatically configure BMS networks during BMS provisioning and restore the BMS network when the network is interrupted due to faults.
  SDI iNIC frontend driver plug-in | This plug-in is installed in the image so that EVS disks can be attached to BMSs. In this way, BMSs can be booted from EVS disks, facilitating quick BMS provisioning.

- Compatibility: compatible with server hardware
- Security: highly stable and licensed
- Restrictions: no restrictions on usage

#### Private Images

A private image contains an OS, preinstalled public applications, and a user's private applications. You can use a private image to create BMSs without having to repeatedly configure them.

Characteristics

- Compatibility: Private images can be used to deploy servers that are of the same model as the source BMS and may fail to deploy servers of other models.
- Functions: You can create and delete private images, as well as create BMSs and reinstall the BMS OS using private images.
- Restrictions: You can create a maximum of 50 private images.

#### Shared Images

A shared image is a private image other users share with you.

#### Application Scenarios

- Deploying software environments in a batch

  Prepare a BMS with an OS, the partition arrangement you prefer, and software installed to create a private image. You can use the image to create batch clones of your custom BMS.

- Backing up a BMS

  Create an image from a BMS to back up the BMS. If the software of the BMS becomes faulty, you can use the image to restore the BMS.

Parent topic: Image