Symptoms
The following warning is displayed on Plesk pre-migration check:
Failed to dump the following data: Subscription (example.com): Web server settings. Not all data may be migrated.
Error message: Command execution failed on the source server 'source' (203.0.113.2) with non-zero exit code.
command: /usr/local/psa/admin/sbin/nginxmng --status
exit code: 1
stdout: ***hidden***
stderr: ***hidden***
Cause
Plesk Migrator extension bug with ID #PMT-4948 which will be fixed in future extension updates.
Resolution
This warning can be safely ignored, as it's only cosmetic. The migration process will skip nginx if it is not installed and should finish without any issues.