Creating a System Disk Image from a Linux ECS

Scenarios

If you have created and configured a Linux ECS based on your service requirements (for example, by installing software and setting up an application environment), you can create a system disk image based on this configured ECS. Then, all new ECSs created from this image will have the same software and environment preinstalled.

Creating a system disk image does not affect the running of services on the ECS or cause data loss.

Background

The following figure shows the process of creating a system disk image from an ECS.

Figure 1 Creating a system disk image and using it to create ECSs

• System disk images are often used for application scale-out. They can also be used for hybrid cloud deployment. You can create system disk images for resource synchronization on and off cloud. The procedure is as follows:
  1. Create a system disk image from an ECS.
     

     If the ECS is created from any of the following images, the system disk image cannot be exported:

     • ISO image

     • Private image created from an Ubuntu public image
  2. Export the image to an OBS bucket. For details, see Exporting an Image.
  3. Download the image file from the OBS bucket.
• You can create an image from a running ECS.

  The image creation does not affect service running on the ECS.

  In this process, do not stop, start, or restart the ECS, or the image creation may fail.

• The time required for creating an image depends on the ECS system disk size, network quality, and the number of concurrent tasks.
• A system disk image will be created in the same region as the ECS that was used to create it.
• If an ECS has expired or been released, you can use the system disk image created from the ECS to restore it.

Prerequisites

Before creating a private image from an ECS:

• Delete any sensitive data the ECS may contain.
• Ensure that the ECS is in the Running or Stopped state.
• Check network configuration of the ECS and ensure that DHCP is configured for the NICs. For details, see Setting the NIC to DHCP.
• Check whether the one-click password reset plug-in has been installed on the ECS. The password reset function on the management console is only available for new ECSs that have this plug-in installed.
• Check whether Cloud-Init has been installed on the ECS. The user data injection function on the management console is only available for new ECSs that have this tool installed. You can use data injection, for example, to set the login password for a new ECS. For details, see Installing Cloud-Init and Configuring Cloud-Init.
• Delete any network rules to prevent NIC name drift on the ECSs created from the image. For details, see Deleting Files from the Network Rule Directory.
• To ensure that the ECSs created from the image support both Xen and KVM virtualization, the Linux ECS used to create the image has to be modified. For instance, the disk IDs in the GRUB and fstab files need to be UUID and native Xen and KVM drivers need to be installed.

  For details, see steps 2 to 6 in Optimization Process.

• If multiple data disks are attached to an ECS used to create a private image, the ECSs created from the image may be unavailable. You need to detach all data disks from the ECS before using it to create an image. For details, see Detaching Data Disks from an ECS.
• If data disks have been attached to the ECS and automatic partition mounting has been configured in the fstab file for the ECS, delete these configurations from the file before using the ECS to create a system disk image.
• Ensure that the system disk capacity of the ECS used to create a system disk image must be no greater than 1 TB.

  If the capacity is greater than 1 TB, you can only use it to create a full-ECS image.

If an ECS is created from a public image, the one-click password reset plug-in and Cloud-Init have been installed by default. You can follow the guide to verify the installation.

Procedure

1. Access the IMS console.
   1. Log in to the management console.
   2. Under Compute, click Image Management Service.

      The IMS console is displayed.

2. Create a system disk image.
   1. Click Create Image in the upper right corner.
   2. Set image parameters.

      Table 1 and Table 2 list the parameters in the Image Type and Source and Image Information areas, respectively.

      Table 1 Image type and source

      Parameter	Description
      Type	Select System disk image.
      Source	Select ECS and select an ECS with required configurations.

      Table 2 Image information

      Parameter	Description
      Encryption	This parameter specifies whether the image will be encrypted. The value is provided by the system and cannot be changed. Only an unencrypted private image can be created from an unencrypted ECS. Only an encrypted private image can be created from an encrypted ECS.
      Name	Set a name for the image.
      Enterprise Project	Select an enterprise project from the drop-down list. This parameter is available only if you have enabled enterprise projects or your account is an enterprise account. To enable this function, contact your customer manager. An enterprise project provides central management of cloud resources on a project.
      Tag	(Optional) Set a tag key and a tag value for the image to make identification and management of your images easier.
      Description	(Optional) Enter a description of the image.

   3. Read and agree to the disclaimer, and click Next.
   4. Confirm the settings and click Submit.

3. Go back to the Private Images page and view the new system disk image.

   The time required for creating an image depends on the ECS system disk size, network quality, and the number of concurrent tasks. When the image status changes to Normal, the image creation is complete.

   

   • Do not perform any operations on the selected ECS or its associated resources during image creation.
   • An ECS created from an encrypted image is also encrypted. The key used for encrypting the ECS is the same as that used for encrypting the image.
   • An image created from an encrypted ECS is also encrypted. The key used for encrypting the image is the same as that used for encrypting the ECS.

Follow-up Procedure

After a system disk image is created, you can:

• Use the image to create new ECSs. For details, see Creating an ECS from an Image.
• Use the image to change the OSs of existing ECSs. For details, see Changing the OS.