diff --git a/openct/setup/__main__.py b/openct/setup/__main__.py
index 59acb2a..0e2d199 100644
--- a/openct/setup/__main__.py
+++ b/openct/setup/__main__.py
@@ -1,7 +1,18 @@
 """Config file generator."""
 
+import os
+
 import yaml
 
+CONFIG_FILE = "config.yml"
+
+if os.path.exists(CONFIG_FILE):
+    user_input = input(
+        f"The config file '{CONFIG_FILE}' already exists. Do you want to overwrite it? (yes/no): "
+    ).lower()
+    if user_input != "yes" and user_input != "y":
+        print("Config file not overwritten. Exiting.")
+        exit()
 
 mt_backup_config = {
     "identity": {
@@ -21,5 +32,5 @@
     },
 }
 
-with open(file="config.yml", mode="a", encoding="utf-8") as file:
+with open(file=CONFIG_FILE, mode="w", encoding="utf-8") as file:
     yaml.dump(mt_backup_config, file, default_flow_style=False)