Elastic Compute Service:Operating system migration

Scenarios

When the operating system of your ECS instance enters the end of life (EOL) phase as described in Operating system lifecycle overview, you may face increased security and usage risks. In this case, we recommend that you replace the operating system that is in the EOL phase as soon as possible. The operating system migration feature lets you retain your existing application data after replacing the operating system, but provides only some operating system migration options.

If you do not need to retain the data on the system disk or require more operating system conversion options, you can change the operating system by replacing the system disk. You can also refer to Operating system maintenance cycle and EOL guidance to obtain the recommended migration solution and detailed handling methods for your current operating system.

Pre-migration assessment

Before performing the migration, we strongly recommend that you understand the migration limits of the corresponding operating system and perform comprehensive testing and validation of all your business applications in the target operating system environment in advance. This helps ensure compatibility and performance between the applications and the target operating system, effectively avoiding issues such as business operation problems or function failures that may occur after migration.

The operating system migration tool does not support hot migration. During migration, the system kernel and software packages of the source instance will be installed or updated, and the instance will automatically restart multiple times, causing business interruptions. Therefore, before migration, you need to create snapshots to back up data and isolate the operating system environment to be migrated to avoid affecting normal business operations.

Migration procedure

1. Optional. Perform the following operations if you want to migrate a CentOS 7 or CentOS 8 operating system to RHEL 7 or RHEL 8. Otherwise, skip this step.

   1. If the Security Center agent is installed on the source operating system, uninstall it.

      Note

      You can reinstall the Security Center agent after the migration and system upgrade are complete. For more information, see the "Manually install the Security Center agent" section of the Install the Security Center agent topic.

      After the agent is uninstalled, Security Center still protects your server for 24 hours. If you want to reinstall the agent, install the agent 24 hours later. If you want to reinstall the agent within 24 hours after the agent is uninstalled, you must run the installation command at least three times and ignore the error messages during the installation. Otherwise, the reinstalled agent is automatically uninstalled.

      1. Go to the Feature Settings page of the Security Center console. Find the server from which you want to uninstall the Security Center agent and uninstall the Security Center agent. For more information, see Uninstall the Security Center agent.

      2. Use a remote connection tool to connect to the server and run the following commands:

         wget "http://update2.aegis.aliyun.com/download/uninstall.sh" && chmod +x uninstall.sh && ./uninstall.sh if ! lsmod | grep AliSecGuard; then echo 'Uninstall Success'; else echo "Uninstall Failed"; f

         If Uninstall Success is returned, the Security Center agent is uninstalled.

   2. Run the following command to upgrade the source operating system to the latest kernel version:

   CentOS 7

   # Back up the source YUM software repository and replace it with the Alibaba Cloud repository of CentOS 7. mv /etc/yum.repos.d/ /etc/yum.repos.d.backup/ mkdir -p /etc/yum.repos.d/ wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo yum clean all yum makecache # Upgrade and restart the operating system. yum -y update reboot

   CentOS 8

   # Back up the source YUM software repository and replace it with the Alibaba Cloud repository of CentOS 8. mv /etc/yum.repos.d/ /etc/yum.repos.d.backup/ mkdir -p /etc/yum.repos.d/ wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.cloud.aliyuncs.com/repo/Centos-8.repo wget -O /etc/yum.repos.d/epel-archive-8.repo http://mirrors.cloud.aliyuncs.com/repo/epel-archive-8.repo yum clean all yum makecache # Upgrade and restart the operating system. yum -y update reboot

2. Open the Replace Operating System dialog box.

   1. Go to ECS console - Instance.

   2. In the top navigation bar, select the region of the ECS instance.

   3. Click the ID of the target instance to go to the instance details page, click All Actions to expand all operation panels, then search for and click Replace Operating System.

3. Select Migrate Operating System. Wait for the system to automatically perform a pre-migration check, which takes about 10 seconds. When the pre-check status changes from to , it indicates that the pre-check has passed.

4. Read the operating system migration notes carefully, select I Acknowledge And Accept These Risks And Authorize Alibaba Cloud To Create Snapshots For All Disks On The ECS Instance. Then click Next.

   Note

   To migrate the operating systems of multiple ECS instances at a time, select the ECS instances whose operating systems you want to migrate.

5. In the Replace Operating System dialog box, select a destination operating system based on your requirements.

   1. Select The Same Destination Operating System: If you migrate the operating systems of multiple ECS instances at a time, you can select this option and specify a destination operating system for all the selected instances.

   2. Select Destination Operating System By Instance: If you migrate the operating systems of multiple ECS instances at a time, you can select this option and specify a destination operating system for each selected instance.

6. Click Check For Migratability to view the migration check results. The check takes about 30 seconds, please be patient. When the status shows , click Migrate.

Migration validation

1. In the Replace Operating System dialog box, click the instance ID. On the Instance Details tab, check whether the operating system of the ECS instance is migrated based on the value of the Instance Status parameter.

   Note

   Approximately 15 to 30 minutes are required to migrate the operating system. This excludes the time that is required to create snapshots. During the migration, you can move the pointer over Replacing Operating System to view the progress of the migration task.

2. If the operating system is migrated, the value of the Instance Status parameter changes from Running (Replacing Operating System) to Running.

   Important

   If the instance status shows Running (Operating System Replacement Failed), it indicates that the operating system migration has failed. You can move the pointer over Operating System Replacement Failed to view the cause of the failure, click Identify Issue & Contact Us to resolve the issue. After the issue is resolved, click Retry Replacement to migrate the operating system of the ECS instance again.

3. After the migration is complete, the instance automatically restarts. The instance ID, image ID, VPC, public and private IP addresses, and hostname remain unchanged. The operating system is changed to the destination operating system. The data on the original system disk is retained. However, your applications may not function as expected due to changes in the environment or dependencies, which can affect your services. Therefore, you must perform tests to verify the outcome of the migration. To roll back the data on the source system disk, you can use the snapshot that was automatically created for backup to roll back a disk.

What to do next

• When you migrate the operating system of an ECS instance, snapshots are automatically created for the instance. After you migrate the operating system of the instance, if you confirm that you no longer need these snapshots, we recommend that you delete the snapshots at the earliest opportunity to prevent additional costs. To keep the snapshots, you can check Snapshots to understand the specific billing rules.

• You can view and manage the history records of operating system migration tasks in the SMC console, or visit Server Migration Center (SMC) to explore more SMC features.

• For migration issues, you can refer to Operating system migration issues (Windows), Operating system migration issues (Linux), and Red Hat migration troubleshooting official documentation.