# Images

#### What Is Image?

An image is an ECS template that contains an OS and may also contain proprietary software and application software, such as database software. You can use images to create ECSs.

Images can be public or private. Public images are provided by the system by default, and private images are manually created. You can use any type of image to create an ECS. You can also create a private image using an existing ECS or external image. This provides you with a simple and fast way to create ECSs tailored to your needs. For example, if you use web services, your image can contain web server configurations, static configurations, and dynamic page code. After you use this image to create an ECS, the web server will run on the newly created ECS.

#### Image Types

Image Type | Description
--- | ---

Public image

A public image is a standard, widely used image. It contains an OS and preinstalled public applications and is available to all users. Public images are very stable and their OS and any included software have been officially authorized for use. If a public image does not contain the application environments or software you need, you can use a public image to create an ECS and then deploy required software as needed.

Private image

A private image contains an OS or service data, preinstalled public applications, and a user's personal applications. Private images are only available to the users who created them.

A private image can be a system disk image, data disk image, or full-ECS image.

- A system disk image contains an OS and pre-installed software for various services. You can use a system disk image to create ECSs and migrate your services to the cloud.
- A data disk image contains only service data. You can use a data disk image to create EVS disks and use them to migrate your service data to the cloud.
- A full-ECS image contains an OS, pre-installed software, and service data. A full-ECS image is created using differential backups and the creation takes less time than creating a system or data disk image of the same size.

Shared image | A shared image is a private image another user has shared with you.

Parent topic: Service Overview