Create all-domains-show-nginx-502-error.md

documentation/docs/articles/domains/all-domains-show-nginx-502-error.md

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+# All Domains show Nginx 502 error
+
+This happens when a third party user/service restarted docker and the floatingip service failed to reload the `/etc/hosts` file with new docker private IP addresses.
+
+To resolve this issue, run:
+
+```bash
+opecncli server-recreate_hosts
+```
+
+Then restart Nginx service:
+
+- soft restart (reload without downtime):
+  ```bash
+  docker exec nginx bash -c "nginx -t && nginx -s reload"
+  ```
+- hard restart (stop and start again):
+  ```bash
+  docker restart nginx
+  ```