Server Migration Center:Operating system migration (Linux)

Background information

When the operating system of your ECS instance enters the end of life (EOL) phase, as described in Overview of operating system lifecycles, you may face increased security and operational risks. We recommend that you replace the operating system as soon as possible. The operating system migration feature of Server Migration Center (SMC) provides several migration solutions. After the migration, the operating system kernel and major system packages are upgraded, while the data on the system disk is retained.

Migration solutions

Migration limitations

Usage notes for migration

Billing

During the migration, the system creates snapshots of all disks on the ECS instance to back up data. You are charged for these snapshots on a pay-as-you-go basis. For more information, see Product Billing.

Procedure

1. (Conditional) To migrate CentOS 7/8 to Red Hat 7/8, you must complete the following operations. Otherwise, skip this step.

   1. If the Security Center client is installed on the source system, you must first uninstall it.

      Note

      You can reinstall it after the migration is complete. For more information, see Manual installation.

      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 Alibaba Cloud Security Center client uninstallation interface and select the instance from which to uninstall the client. For more information, see Uninstall the client.

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

         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"; fi

         The Uninstall Success message indicates that the Security Center client is uninstalled.

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

      CentOS 7

      # Back up the original yum software source and update it to the Alibaba Cloud CentOS 7 source.
      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
      # Update and restart the system.
      yum -y update
      reboot

      CentOS 8

      # Back up the original yum software source and update it to the Alibaba Cloud CentOS 8 source.
      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
      # Update and restart the system.
      yum -y update
      reboot

2. Migrate the operating system.

   Fast migration (Recommended)

   Note

   To use this method, you must install Cloud Assistant Agent on the ECS instance if it was purchased before December 1, 2017, was created from a custom image you uploaded, or is a third-party cloud server. ECS instances created from public images after December 1, 2017 have the required Cloud Assistant Agent pre-installed, so no action is required.

   1. Go to the SMC console-Cloud Migration-OS Migration.

   2. On the OS Migration page, click Start Migration.

   3. In the Migrate Operating System dialog box, select the ECS instance to migrate by its instance ID and region, then click Pre-check.

      

   4. In the Migrate Operating System dialog box, the system automatically performs a pre-migration check, which takes about 10 seconds.

      • If the pre-check status changes from to , the pre-check is successful.

      • If the pre-check status changes from to , the pre-check failed. Follow the prompts on the interface to resolve the issue and then try migrating again.

   5. After you carefully read the notes for operating system migration, select I acknowledge and accept these risks and authorize Alibaba Cloud to create snapshots for all disks on the ECS instance, and then click Next.

      

   6. In the Migrate Operating System dialog box, you can select the destination operating system.

      • Select the Same Destination Operating System: If you perform a batch migration, you can migrate multiple instances to the same operating system.

      • Select Destination Operating System by Instance: If you perform a batch migration, you can migrate multiple instances to different operating systems.

   7. Click Check for Migratability to view the migration check result.

      The check takes about 30 seconds.

      • : The operating system can be migrated.

      • : Migration is not supported. You can view the reason for the failure in the interface prompts.

   8. Click Migrate.

      You can view the progress of the operating system migration on the Migrate Operating System page.

      Warning

      During the operating system migration, do not manually stop, restart, or release the ECS instance. Do not use O&M scripts to perform these operations. Otherwise, the migration fails.

   Staged migration

   Step 1: Import the migration source

   A migration source is the data center server, VM, or cloud host from another platform that you plan to migrate.

   Command-line one-click import of migration source (Recommended)

   Important

   • The source server must have public network access. If the source server has firewall restrictions, see What are the endpoints of SMC? to obtain the SMC domain names and ports, and add them to the firewall whitelist.

   • If your source server cannot access the public network or you want to improve migration efficiency by transferring data over a private network, see the private network migration solution.

   1. Go to SMC console - OS Migration.

   2. On the OS Migration page, click Import Migration source.

   3. Configure the parameters as prompted on the page and copy the activation code command. The parameters are described in the following table.

      Parameter	Description
      Migration Source Type	Select Alibaba Cloud ECS Instance.
      Import Method	Select Use CLI To Import Server.
      Activation Quota	The number of migration sources that can be activated by the activation code. The value ranges from 1 to 1000. The default value is 200.
      Validity Period	The validity period of the activation code. The value ranges from 1 to 90 days. The default value is 90 days.
      Activation Code	After generating the activation code, copy the command. Perform the following steps: Click Generate. Click the Linux Shell tab. Click Copy to copy the activation code command.

   4. Log on to the source server, and then paste and run the copied command with administrator privileges to import the migration source.

      1. Log on to the Linux source server.

      2. Paste and run the copied command with administrator privileges to import the migration source.

         

         After you run the command, a message similar to Import Source Server [s-bp18x8751kgz2oyh****] Successfully! appears, which indicates that the migration source was imported successfully.

   5. On the Operating System Migration page of the SMC console, view the status of the migration source in the Real-time Migration Status column.

      • If the status of the migration source is Migration Source Online, the migration source is successfully imported.

      • If the migration source is in another state, the import failed. Troubleshoot the failure based on the following solutions and then import the migration source again:

        • Troubleshoot the failure based on the error message in the console or the log file in the SMC client installation directory. By default, the SMC client is installed in /smc.

        • For information about common issues and their solutions, see SMC FAQ and Troubleshoot errors.

   Import a migration source using the SMC client

   For more information about the SMC client, see SMC client usage guide.

   1. Go to SMC console - OS Migration.

   2. On the OS Migration page, click Import Migration source.

   3. On the Import Migration Source page, configure the parameters. The following table describes the parameters.

      Parameter	Description
      Migration Source Type	Alibaba Cloud ECS Instance
      Import Method	Select Client Import.
      Import Description	After the Import Description, download the corresponding SMC client based on the source server's operating system (Linux or Windows) and bit version (32-bit or 64-bit).

   4. Import the migration source.

      Important

      Do not close the SMC client during the migration. Otherwise, the migration source will lose its connection to the SMC console and the migration will fail.

      1. Use a remote connection tool that supports file transfer, such as WinSCP, to upload the SMC client to the Linux source server.

      2. Remotely connect to the Linux source server and unzip the SMC client package.

         This example uses the Linux 64-bit General-purpose Edition. If you use a different version of the SMC client, replace the package name in the command with the actual downloaded file name.

         tar -zxvf go2aliyun_client.tar.gz

         Note

         The Linux 64-bit ARM Edition supports the g6r general-purpose and c6r compute-optimized instance families. For more information about instance families, see Enterprise-level Arm-based compute instance families.

      3. (Optional) As needed, filter and exclude files or directories that do not need to be migrated.

         Important

         If you enable block replication for migration, you cannot exclude files or directories from migration.

      4. Obtain an activation code or an AccessKey pair.

         • (Recommended) In the Description section of the SMC console, click Generateand copy the activation code.

         • Obtain an AccessKey pair: An AccessKey pair for an Alibaba Cloud account includes an AccessKey ID and an AccessKey secret. If you have not created an AccessKey pair, you must create one. For more information, see Create an AccessKey pair.

      5. In the SMC client folder, run the following commands to start the SMC client.

         cd go2aliyun_client_linux_x86_64
         sudo chmod +x go2aliyun_client
         sudo ./go2aliyun_client

      6. Enter the activation code or AccessKey pair as prompted. This example uses an activation code:

         After you enter the activation code or AccessKey pair, the following prompts may appear:

         • If the source system does not have a snapshot driver installed, the SMC client prompts you, as shown in the following figure. You can choose whether to install the snapshot driver based on your needs.

           • If you enable block replication when you create the migration task, enter yes to automatically install the snapshot driver.

           • If you do not enable block replication when you create the migration task, enter no.

           Important

           If the snapshot driver fails to install, do not enable block replication when you create the migration task. Otherwise, the migration will fail.

           

         • Most mainstream source systems have rsync installed by default. If it is not installed, the SMC client prompts you. Enter yes to automatically install rsync, as shown in the following figure.

         • If SELinux is enabled on the source system, the SMC client prompts you to disable it. Enter yes to automatically disable SELinux, as shown in the following figure.

         When a message similar to Import Source Server [s-bp11npxndknsycqj****] Successfully! appears, it indicates that the migration source was imported successfully.

         Note

         If importing the migration source fails, you can troubleshoot the issue based on the displayed message, and then run the following commands in sequence to exit the background program and re-import the migration source. For more information about common issues and solutions, see SMC FAQ and Troubleshooting.

         sudo ./go2aliyun_client --abort
         sudo ./go2aliyun_client

   5. On the Operating System Migration page of the SMC console, view the status of the migration source in the Real-time Migration Status column.

      • A status of Migration SourceOnline indicates a successful import.

      • If the status is not Source Online, the import failed. Troubleshoot the issue using the following methods and then re-import the source.

        • Troubleshoot the failure based on the error message in the console or the log file in the SMC client installation directory. By default, the SMC client is installed in /smc.

        • For common issues and solutions, see SMC FAQ and Troubleshooting.

   Step 2: Migration configuration

   1. Find the migration source that you want to manage and click Start Migration in the Actions column.

   2. In the Migration Configuration dialog box, configure the parameters.

      The following table describes the operating system migration parameters:

      • Current Operating System: The current operating system is displayed by default and cannot be modified. Example: CentOS 7.

      • Destination Operating System: From the drop-down list, select the operating system to which you want to migrate. Example: Alibaba Cloud Linux 3.

      • Migration Drill (Optional):

        Decide whether to enable Migration Drill. This feature is enabled by default and is supported only for Linux operating system migrations. For more information, see Configure a migration drill.

        Note

        A migration drill simulates and verifies a migration solution before the actual migration. It helps you understand the feasibility and risks of the migration solution, which reduces potential problems and data loss during the actual migration.

        A migration drill can help you quickly identify potential problems, provide solutions, and improve the success rate of the migration.

      • Execution Method (Conditional):

        If Migration Drill is enabled, you can select a migration drill execution method from the Execution Method drop-down list. The default option is Drill And Migrate.

        The following list describes the differences between the two methods:

        • Drill Only: Creates only a migration drill task. After the migration drill is complete, if an operating system migration is required, you must manually start the migration task.

        • Drill And Migrate: After the migration drill is complete, if no drill items are in the Critical state, the system automatically starts the operating system migration task.

   3. Click Start Migration. In the Please Confirm Operating System Migration dialog box, carefully read the notes and then click I Confirm I Have Been Informed.

   4. On the Operating System Migration page, view the real-time migration status.

      Warning

      During the operating system migration, do not manually stop, restart, or release the Linux instance. Do not use O&M scripts to perform these operations. Otherwise, the migration fails.

Verify the migration result

• If the real-time migration status is Completed, the operating system migration is successful.

  

  Note

  After the migration task is complete, the ECS instance automatically restarts. During the system initialization phase, operations such as updating software packages are performed. Do not perform any operations on the ECS instance until the system successfully starts. The system initialization phase takes about 15 to 30 minutes. The specific duration depends on the number of system software packages.

  In the Actions column for the destination migration source, click View Destination Instance. Then, on the instance details page, check whether the operating system is migrated to the destination operating system.

  Important

  After the migration, the source instance is migrated to the new system kernel and software packages. The original system disk data remains unchanged. However, applications may not run as expected due to changes in the environment or dependencies, which can cause business failures. You must perform thorough testing and verification.

• If the Real-time Migration Status is Error, the migration task has encountered an error.

  In this case, you need to troubleshoot the problem and retry the migration:

  1. In the Actions column, click Troubleshoot Errors. Use the error code and error message to resolve the issue. For more information, see SMC FAQ and Troubleshooting.

  2. After you resolve the issue, click Retry Migration Job in the Actions column. The migration will resume.

     Important

     If the intermediate instance has been released, you must start the migration again. For more information, see What do I do if I accidentally release the intermediate instance?.

  To roll back the data on the source system disk, you can use the automatically created backup snapshot to restore the data. The steps are as follows:

  1. Go to the ECS console - Snapshots.

  2. In the Actions column of the automatically created backup snapshot, click Roll Back Disk.

  3. In the Roll Back Disk dialog box, click Confirm.

Clean up resources

During the migration, SMC creates pay-as-you-go snapshots named SMC_Backup_Snapshot_XXX to back up the data on the ECS instance's cloud disks. If you no longer need these snapshots, delete them promptly to avoid unnecessary charges. For more information, see Delete a snapshot.