add swap check command before setup instructions

README.md

@@ -58,7 +58,13 @@ cat /etc/os-release
 
 ### Swap (recommended)
 
-If your VPS has no swap, add a 2 GB swapfile to prevent OOM kills:
+Check current memory and swap:
+
+```bash
+free -h
+```
+
+If swap shows `0B`, add a 2 GB swapfile to prevent OOM kills:
 
 ```bash
 sudo fallocate -l 2G /swapfile