An error message that indicates insufficient disk space or memory appears - Server Migration Center

Problem description

During the migration of an operating system, one of the following error messages appears:

Available system memory is less than 300M, memory requirement is not satisfied.
Total system memory is less than 512M, memory requirement is not satisfied.
Available system storage is less than 2G, storge requirement is not satisfied.
To ensure the migration, this machine must have 2G free space on disk and 300MB RAM available.
To ensure the migration, this machine must have 512MB RAM at least totally.
To ensure the migration, this machine must have 4G free space on disk and 600M RAM available
Memory detected: *MiB, required: *MiB

Cause

The disk space of the root directory in the operating system to be migrated is insufficient or the available memory is insufficient. Therefore, the operating system failed to be migrated. The following table lists the causes of different error messages.

Migration scenario	Error message	Cause
CentOS 7 -> Alibaba Cloud Linux 2 CentOS 8 -> Alibaba Cloud Linux 3 Red Hat 8 -> Alibaba Cloud Linux 3	Available system memory is less than 300M, memory requirement is not satisfied.	The available memory of the server is less than 300 MiB.
	Total system memory is less than 512M, memory requirement is not satisfied.	The total memory of the server is less than 512 MiB.
	Available system storage is less than 2G, storge requirement is not satisfied.	The available space of the system disk is less than 2 GiB.
CentOS 7 -> AnolisOS 7 CentOS 8 -> AnolisOS 8	To ensure the migration, this machine must have 2G free space on disk and 300MB RAM available.	The available space of the system disk is less than 2 GiB and the available memory is less than 300 GiB.
CentOS 7 -> AnolisOS 7 CentOS 8 -> AnolisOS 8	To ensure the migration, this machine must have 512MB RAM at least totally.	The total memory of the server is less than 512 MiB.
CentOS 7 -> Alibaba Cloud Linux 3 CentOS 7 -> AnolisOS 8 Red Hat 7 -> Alibaba Cloud Linux 3 Alibaba Cloud Linux 2 -> Alibaba Cloud Linux 3	To ensure the migration, this machine must have 4G free space on disk and 600M RAM available	The available space of the system disk is less than 4 GiB and the available memory is less than 600 GiB.
	Memory detected: MiB, required: MiB	The total memory of the server of the x86_64 architecture is less than 1.5 GiB. The total memory of the server of the aarch64 architecture is less than 2 GiB.

Solution

Connect to the Elastic Compute Service (ECS) instance whose operating system you want to migrate. For more information, see Connect to a Linux instance by using a password or key.
Clean up disk space or suspend some service programs.
- If the disk space of the root directory is insufficient, perform the following operation:
  Run the following command to clean up the /tmp and /var/log directories to release the disk space:
  Warning
  Make sure that the files are no longer needed before you delete the files. Otherwise, your business may be affected.
```
rm -rf /tmp/*
rm -rf /var/log/syslog.*    # Delete the earlier syslog files.
```
- If the memory is insufficient, perform the following operation:
  Suspend some service programs, such as the Java program or NGINX process, to release the memory. After you migrate the operating system, manually restart the suspended service programs. For example, run the following commands to suspend the NGINX process:
```
ps aux | grep nginx # View the Process Identifier (PID) of the NGINX process.
kill -SIGSTOP <nginx-pid> # Suspend the NGINX process.
```
After the error is resolved, run the SMC client and retry the migration job. For more information, see Run the SMC client.
If you have suspended a process, manually start the suspended process after migration.
For example, run the following command to start the NGINX process:
```
kill -SIGCONT <nginx-pid>
```