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    :Troubleshoot post-migration instance downtime

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    :Troubleshoot post-migration instance downtime

    Last Updated:Apr 27, 2026

    Resolve boot failures after ECS instance migration, such as kernel panics, blue screens, or driver incompatibilities.

    Background

    ECS instance families and public images use different virtualization technologies. Drivers must match the virtualization architecture:

    • Legacy families (ecs.t1, ecs.s1): Use Xen virtualization. Images must contain Xen drivers.

    • KVM families (e.g., ecs.g5): Use KVM virtualization. Images must contain virtio drivers.

    • Shenlong architecture (e.g., ecs.g7): Use the proprietary Shenlong architecture. Images must contain optimized virtio drivers.

    These drivers are built into the OS kernel. Older kernels may lack required drivers or contain outdated versions. In such cases, manually install or update the drivers.

    Before you begin

    Existing issues in the source instance can cause registry corruption, file system errors, or boot failures after migration. Complete the following before you migrate:

    Shenlong architecture incompatibility with legacy OS

    The Shenlong architecture does not support the following legacy operating systems due to kernel limitations:

    • Windows: Windows Server 2003 and earlier. Windows Server 2008 Standard requires clearing Xen registry keys.

    • CentOS / Red Hat: 5.8 and earlier (kernel 2.6.18-348 or older).

    • Debian: Earlier than 6.09. Upgrade to 6.09+ to resolve KVM compatibility issues.

    • FreeBSD: Earlier than 11. FreeBSD 11/12 require Alibaba Cloud patches.

    • Ubuntu: 10 and earlier. Ubuntu 12 boots on kernel 3.2.

    • SUSE Linux Enterprise Server: 10 and earlier.

    • OpenSUSE: Earlier than 13.

    • Gentoo: Alibaba Cloud images support Xen only. Upgrade to the latest version for KVM.

    This list applies to 6th-generation instances. 7th-generation and later instances have stricter requirements.

    Upgrade the OS by replacing the system disk

    Legacy operating systems have reached End of Maintenance (EOM) and pose significant security risks. Upgrade to a supported OS. See Operating system lifecycle.

    Alibaba Cloud provides public images for mainstream Linux and Windows distributions. Replace the system disk with a public image to upgrade.

    To migrate data and applications, replace the operating system.

    • Recover data.

      Detach the old system disk and attach it to the new instance as a data disk to copy your files.

    • Migrate services and applications.

      • Reinstall applications and services on the new system disk.

      • Move database files and configurations from the data disk to the new environment.

    Pros & Cons:

    • Pros: Latest features, security patches, and official support. One-click replacement via the console.

    • Cons: Manual data backup and application redeployment required.

    Upgrade the OS to the latest minor version

    If you cannot replace the OS, update to the final minor release (e.g., CentOS 5 to 5.11).

    Pros & Cons:

    • Pros: Preserves existing data and configurations.

    • Cons: The OS remains EOL. Security vulnerabilities persist, and modern features (CentOS 7/8) are unavailable.

    Use an earlier-generation instance

    If your legacy application requires an older environment, downgrade to a 5th-generation instance family (e.g., ecs.n, ecs.xn, ecs.c5) that does not use the Shenlong architecture.

    Virtio driver configuration failure

    If the KVM virtio driver is missing or misconfigured, the instance may fail to boot after migration. Common causes:

    • Linux: The virtio driver is not installed or configured.

    • Windows: Drivers failed to install during the ISO phase.

    • Windows: The Windows registry is corrupted.

    • Security software: Third-party tools (e.g., 360 Total Security) blocked the driver installation.

    Solutions

    • Install virtio driver.

    • Linux: If the kernel is corrupted, reinstall the official distribution kernel.

    • Windows: Contact technical support to attach the WinPE 3.0 ISO. Boot into WinPE and check the virtio driver in Device Manager. Install the driver manually if missing.

    • Windows: Run SFC (System File Checker) to verify system integrity. Uninstall third-party security software (e.g., 360 Total Security) that may block driver installation.