An ECS image is a template that contains the operating system and pre-configuration data needed to launch an ECS instance. Every ECS instance requires an image at creation time. An image can include only the system disk, or both the system disk and data disks.
An image is specific to:
Region — images exist within a region; not all image types are available in all regions
Architecture — 32-bit or 64-bit, with memory and CPU constraints
Instance type — the image must be compatible with the instance type you select
This topic covers image types, how to choose an image, the relationship between images and snapshots, limits, and available operations.
Image types
Alibaba Cloud provides five image types. The type determines where the image comes from and what level of technical support is available.
| Image type | Source | Trust level | Technical support |
|---|---|---|---|
| Public images | Officially provided by Alibaba Cloud; licensed and security-tested | Highest | Alibaba Cloud Linux: Alibaba Cloud. Open source images: community (Alibaba Cloud assists with troubleshooting). Commercial images: Alibaba Cloud + OS vendor jointly. |
| Custom images | Created from your ECS instances or snapshots | High | Images derived from public images: same as public image support. Imported open source images: none. Imported commercial images with an Alibaba Cloud license: Alibaba Cloud + OS vendor jointly. |
| Shared images | Shared by another Alibaba Cloud account | Medium | Contact the account that shared the image. |
| Alibaba Cloud Marketplace images | Provided by Alibaba Cloud or independent software vendors (ISVs) via Alibaba Cloud Marketplace; includes pre-installed software tested for security and stability | Medium–High | Images from Alibaba Cloud: same as public image support. Images from ISVs: the ISV. |
| Community images | Published by Alibaba Cloud users for public use | Lowest | None from Alibaba Cloud. |
Technical support applies only before the end of life (EOL) of an image. For post-EOL support options, see Operating system lifecycle.
Alibaba Cloud regularly updates public image versions to deliver new features and security patches. The ECS buy page always shows the latest version. To launch an earlier version, call the RunInstances API operation and specify the image ID. Alibaba Cloud also synchronizes images from official open source communities to the Alibaba Cloud image site.
Security is a shared responsibility. Alibaba Cloud secures the underlying cloud platform (hardware, software, and network). You are responsible for ECS instance security — including OS updates, security patches, software package configuration, and security group settings. See ECS instance security.
Choose an image
Select an image based on the following factors.
Region availability
Images are region-specific resources. Before choosing an image, confirm that the image type is available in your target region.
| Image type | Regional availability |
|---|---|
| Public images | All regions |
| Alibaba Cloud Marketplace images | Only regions where the image was released |
| Community images | Only regions where the image was released |
| Custom images | The region where you created or imported the image; copy to other regions as needed |
Operating system
Select an operating system based on your technology stack, team expertise, and compliance requirements. For a full list of available OS versions, see Public image overview.
| OS | Best for |
|---|---|
| Windows Server | Windows applications, enterprise web services, SQL Server databases, file and print services |
| Alibaba Cloud Linux | Workloads requiring a CentOS-compatible environment with Alibaba Cloud optimizations |
| Anolis OS | Open source workloads |
| CentOS | Legacy compatibility only — CentOS is no longer maintained and not recommended for new deployments |
| RHEL | Enterprise applications requiring Red Hat support — note that RHEL incurs OS license fees |
Instance type compatibility
Images specify system architecture, memory requirements, and boot program. Match these to your instance type before launching.
| System architecture | Suitable memory size | Instance type requirement |
|---|---|---|
| 32-bit | Less than 4 GiB | Memory ≤ 4 GiB; CPU up to 4 cores (Windows) |
| 64-bit | 4 GiB or more | Memory > 4 GiB |
Instance types with 4 GiB of memory or more do not support 32-bit images.
For boot mode compatibility between images and instance types, see Instance boot modes.
Use case and customization needs
| Need | Recommended image type |
|---|---|
| Clean OS environment with no pre-installed software | Public image |
| Pre-configured environment with your own software and settings | Custom image |
| Specific application stack ready to deploy | Alibaba Cloud Marketplace image |
Fees
Using a paid commercial image, or creating an instance from one, incurs OS license fees. Review image pricing before selecting a commercial image. For billing details, see Images.
Both images and snapshots capture ECS instance data, but they serve different purposes.
An image is a template used to create and launch ECS instances. A snapshot is a point-in-time backup of a cloud disk. The following figure shows how instances, snapshots, and custom images relate: a snapshot backs up an instance at a specific point in time, and both an instance and a snapshot can be used to create a custom image, which can then launch new instances.
| Image | Snapshot | |
|---|---|---|
| Definition | Full backup of an ECS instance: OS, configurations, installed software, and data | Point-in-time backup of a single cloud disk or a consistent group of cloud disks (snapshot-consistent group) |
| Create instances directly | Yes | No — convert to an image first |
| Disk coverage | Always includes system disk; optionally includes data disks | System disk and data disks independently |
| Restore scope | Replace the system disk of the source instance or another instance; or launch new instances | Restore data on the source disk |
| Typical scenarios | Batch deployment; cross-region or cross-zone instance migration; environment replication | Scheduled disk backups; pre-change backups (system updates, disk resizing); disk data migration |
How images and snapshots interact
Creating a custom image from an instance automatically creates a snapshot of the system disk and each data disk. These snapshots together constitute the custom image.
Creating a custom image from a snapshot uses only that snapshot. For details, see Create a custom image from a snapshot.
Deleting a custom image lets you choose whether to retain or delete the associated snapshots.
Deleting a snapshot that is associated with an image requires deleting the image first. For details, see Delete a snapshot.
Limits
| Item | Limit | How to raise |
|---|---|---|
| Maximum custom images per account per region | View quota via quota ID q_user-image-count | View or increase ECS quotas |
| Maximum accounts a custom image can be shared with | View quota via quota ID q_user-per-image-shared-user-count | View or increase ECS quotas |
| 32-bit image support | Not supported on instance types with 4 GiB of memory or more | N/A |
Image operations
Find an image
Search across public images, Alibaba Cloud Marketplace images, custom images, and shared images when creating an instance. See Find an image.
Manage custom images
| Operation | Description | Reference |
|---|---|---|
| Create | Create a custom image from a running instance or an existing snapshot to capture the system environment. | Create from an instance and Create from a snapshot |
| Import | Bring images from on-premises environments or other cloud providers into Alibaba Cloud as custom images. | Import an image |
| Update | Use CloudOps Orchestration Service (OOS) to update software and configurations in a custom image without recreating it. | Update a custom image |
| Copy | Replicate a custom image to another region, or change the encryption status of an image within or across regions. | Copy a custom image |
| Share | Share a custom image with other Alibaba Cloud accounts so they can launch instances from it. | Share a custom image |
| Export | Export a custom image to an OSS bucket and download it to an on-premises device. | Export a custom image |
| Modify | Update the name, description, NVMe drive settings, or boot mode of a custom image. | Modify image attributes and tags |
| Delete | Remove a custom image you no longer need. | Delete a custom image |
Use Image Builder
Image Builder provides a one-stop solution for building custom images. With Image Builder, you define an image template that specifies the source image and components, then run an image-building task. The task handles image repair, testing, cross-region distribution, and cross-account sharing based on the template configuration.