Data and system changes after SMC server migration - Server Migration Center

After an SMC migration, certain system configurations and data may change on the target instance. Review the changes listed below for Linux and Windows instances and adjust settings as needed.

Linux instance changes after migration

System configuration changes

SMC makes the following changes to ensure the migrated server runs on ECS. These changes do not affect source server services.

Automated change	Reason
Fix boot files	Affected files: /boot/grub/grub.conf, /boot/grub/grub.cfg, or /boot/grub2/grub.cfg Replaces the system disk UUID so the OS can detect and boot from the correct disk.
Fix automatic mount configuration file	Affected file: etc/fstab Ensures data disks are detected and automatically mounted on instance startup.
Disable SELinux	Affected file: /etc/selinux/config Disabled to prevent application startup failures caused by its access control policies. Re-enable SELinux after migration if needed, after assessing the security impact.
Fix cloud-init configuration	Affected file: /etc/cloud/cloud.cfg Ensures the migrated instance can receive and run cloud platform initialization configurations.
Rebuild initramfs	Affected file: /boot/initramfs*.img Installs cloud environment drivers such as the virtio driver.
Install dependencies	Installs block replication dependencies: gcc and make.
Install and run the SMC client	The default installation directory for the SMC client is `/smc`.

The following items require manual changes.

Issue

Cause

SSH remote logon fails

SMC copies the NIC configuration from the source server. After migration, the original NIC name may not match the ECS naming convention (such as eth0 or eth1), preventing the network service from starting. Manually modify the configuration and restart the service.

Example: rename the NIC from ens192 to eth0. Adjust as needed:

Log on to the migrated ECS instance.

To migrate to an image, you must first create an instance from a custom image or a shared image.
1. Go to ECS console - Instances. In the top-left corner, select the region and resource group for the target resource.
2. Go to the Instance page. Click Connect in the actions column, then click Sign in now in the dialog box that appears. Log in as prompted to go to the terminal page.
Run cd /etc/sysconfig/network-scripts/ to go to the NIC configuration directory.
Find the NIC configuration file ifcfg-ens192 and rename it by running sudo mv ifcfg-ens192 ifcfg-eth0.
Run sudo vi ifcfg-eth0. Change the DEVICE parameter to eth0 and the BOOTPROTO parameter to dhcp. Then, save the file and exit.

Restart the network service to apply the configuration.

Operating system	Restart command
Alibaba Cloud Linux 2 CentOS 7 Red Hat 7 Anolis 7 SUSE Linux 11/12/15 OpenSUSE 15/42	`sudo service network restart` or `sudo systemctl restart network`
CentOS 6 Red Hat 6	`sudo service network restart`
Alibaba Cloud Linux 3 CentOS 8 Red Hat 8 Anolis 8 Fedora 33/34/35	`sudo systemctl restart NetworkManager` or `sudo reboot`
Ubuntu 18/20/22 Debian 12	`sudo netplan apply`
Ubuntu 14/16 Debian 8/9/10/11	`sudo systemctl restart networking` or `sudo reboot`

The hostname changes.

The hostname changes during migration. You can reconfigure it as needed.

Original logon password is invalid

The original password becomes invalid after migration.

Migration to an image: Set the logon password in the Logon Credentials section when you create an instance from a custom image or shared image.
Migrating to an ECS instance: Reset the password.

Storage and data changes

Issue	Reason
Disk device name changes	LVM logical volumes spanning multiple disks are converted to regular partitions. SMC preserves LVM structures only on single-disk setups. For multi-disk VGs or LVs, the logical volume (such as /dev/mapper/test-lvm1) migrates to a regular partition (such as /dev/vdb1) on a cloud disk. Data is retained. Storage device names may change after migration. NVMe or sda device names become NVMe on instances with NVMe drives, or vda on instances with virtio drives. This is expected and does not affect usage.
The size displayed by the `du` command is smaller than the size displayed by `ls -l`	By default, SMC uses the '--sparse' option. Sparse files occupy only their actual data size on the target instance, so their logical size exceeds their physical size. This does not affect usage. To fully copy sparse files, add '--no-S' to 'sync.options' in the 'client_data' file and restart the migration.
Data inconsistency after migration	Services are not stopped during migration. Active write operations during migration cause data inconsistency. Stop all disk writes before starting the migration. File filtering rules are set. SMC filters out certain files and directories by default. Temporary files are not migrated. SMC skips temporary files such as virtual memory, cache, and backup snapshot data. The file system is rebuilt. File-based copy rebuilds the partition's file system. Metadata such as inode size and storage format may change, causing up to 10% difference in reported disk usage.
Docker environment lost	SMC fully migrates the Docker environment only with block replication enabled. Considerations for enabling block replication.

Windows instance changes after migration

System configuration changes

Issue	Solution
Hostname changes	The hostname changes after migration. You can configure it as needed.
Invalid original logon password	The logon password is changed after migration. Migrate to an image: Set the logon password in the Logon Credentials section when you create an instance using a custom image or a shared image. Migrate to an ECS instance: Reset password.
Install and run the SMC client	The default installation directory for the SMC client is `C:\smc`.

Storage and data changes

Issue	Reason
Drive letter changes	On first boot, Windows reassigns drive letters sequentially, which may differ from the original assignment. You can manually reassign them. Log on to the migrated ECS instance. If you are migrating to an image, you must first create an instance from a custom image or a shared image. Go to ECS console - Instances. In the top-left corner, select the region and resource group for the target resource. Go to the Instance page. Click Connect in the actions column, then click Sign in now in the dialog box that appears. Select Terminal for Connection Method, enter your username and password, then log in. On the Windows Server desktop, right-click the icon and select Disk Management. In Disk Management, right-click the target volume and select Change Drive Letter and Paths. Follow the on-screen instructions.
A GPT partition becomes an MBR partition	This does not affect data operations. For compatibility, SMC converts GPT to MBR on data disks smaller than 2 TiB. To expand beyond 2 TiB later, you must transform the partition to a GPT partition.
The dynamic disk structure is not copied	SMC does not migrate Windows dynamic disk structures. Dynamic disks are converted to basic disks after migration.