diff --git a/bistu_wifi/__main__.py b/bistu_wifi/__main__.py
index 6b3fe90..45201f3 100644
--- a/bistu_wifi/__main__.py
+++ b/bistu_wifi/__main__.py
@@ -16,7 +16,7 @@ else:
     XDG_CONFIG_HOME = os.path.join(os.environ['HOME'], '.config')
 
 DEFAULT_HOST = '10.1.206.13'
-DEFAULT_CONFIG_LOCATION = os.path.join(XDG_CONFIG_HOME, 'bistu-wifi/auth.ini')
+DEFAULT_CONFIG_LOCATION = [ os.path.join(XDG_CONFIG_HOME, 'bistu-wifi/auth.ini'), '/etc/bistu-wifi/auth.ini' ]
 
 
 def main():
@@ -39,31 +39,53 @@ def main():
                         type=str, help='host to send login/logout request to, default use 10.1.206.13')
     parser.add_argument('-o', '--logout', action='store_true',
                         help='logout bistu wifi. try to login if not privided')
-    parser.add_argument('-c', '--config', nargs='?', default=DEFAULT_CONFIG_LOCATION,
-                        type=str, help='load info(username, password, host) from config file. '
+    parser.add_argument('-c', '--config', nargs='?', default=None,
+                        type=str, help=f'load info(username, password, host) from config file.'
                         f'Will try {DEFAULT_CONFIG_LOCATION} if not provided.')
-    parser.add_argument('--notime', action='store_true',
+    parser.add_argument('--no-config', action='store_true',
+                        help='don\'t use any config file')
+    parser.add_argument('--no-time', action='store_true',
                         help='don\'t output time field in log')
 
     args = parser.parse_args()
 
     log_level = logging.DEBUG if 'BISTU_WIFI_DEBUG' in os.environ else logging.INFO
     log_fmt = '%(levelname)s : %(funcName)s : %(message)s'
-    if not args.notime:
+    if not args.no_time:
         log_fmt = '%(asctime)s : ' + log_fmt
 
     logging.basicConfig(level=log_level, format=log_fmt)
 
-    username = None
-    password = None
-    host = DEFAULT_HOST
+    username  = None
+    password  = None
+    host      = DEFAULT_HOST
     is_logout = False
 
+    # Load config from file
+    #   Try files [ global_default, user_default ] if args.config not provided,
+    #   Try file specified by user                 if args.config provided
+    #
+    # After these judgements, the config file must exist or is None
+    config_file = None
     if args.config is not None:
-        logger.info('loading info from config file %s ...', args.config)
+        config_file = args.config
 
+        if not os.path.exists(config_file):
+            logger.error('config file not exists: %s', config_file)
+    else:
+        for f in DEFAULT_CONFIG_LOCATION:
+            if os.path.exists(f):
+                config_file = f
+                break
+
+    if args.no_config:
+        config_file = None
+
+    # the config_file must exists now
+    if config_file is not None:
+        logger.info('loading info from config file %s ...', config_file)
         config = configparser.ConfigParser()
-        config.read(args.config)
+        config.read(config_file)
 
         d_section = config['DEFAULT']
 
@@ -71,6 +93,7 @@ def main():
         password = str(d_section['password']) if 'password' in d_section else password
         host     = str(d_section['host'])     if 'host'     in d_section else host
 
+    # override with command paramter
     username = args.username if args.username is not None else username
     password = args.password if args.password is not None else password
     host     = args.host     if args.host     is not None else host