# Product Introduction

#### Image Management Service

An image is a server or disk template that contains an operating system (OS) or service data and necessary software, such as database software. IMS provides public, private, and shared images.

Image Management Service (IMS) allows you to manage the entire lifecycle of your images. You can create ECSs or BMSs from public, private, or shared images. You can also create a private image from a cloud server or an external image file to make it easier to migrate workloads to the cloud or on the cloud.

#### Basic Concepts

Public image

A public image is a standard OS image provided by the cloud platform and is visible to all users. It consists of an OS and pre-installed public applications. You can deploy personal applications as needed.

Private image

A private image is an image available only to the image owner. It contains an OS, pre-installed public applications, and the image owner's private applications. Using a private image to create servers removes the need to configure multiple servers repeatedly.

External image file

An external image file is a template that can be used to create ECSs or BMSs. The template provides information required to create the servers, including the OS and pre-installed applications.