diff --git a/main.py b/main.py
index 99f0ba8..05f4c8a 100644
--- a/main.py
+++ b/main.py
@@ -32,18 +32,55 @@ log = logging.getLogger("rich")
 log.setLevel(logging.DEBUG)
 
 
-config = configparser.ConfigParser()
+class ConfigParser(configparser.ConfigParser):
+    """Can get options() without defaults
+
+    Taken from https://stackoverflow.com/a/12600066.
+    """
+
+    def options(self, section, no_defaults=False, **kwargs):
+        if no_defaults:
+            try:
+                return list(self._sections[section].keys())
+            except KeyError:
+                raise configparser.NoSectionError(section)
+        else:
+            return super().options(section)
+
+
+ini_defaults = []
+internal_defaults = {
+    "self_name": "mvw-dl",
+    "tmp_base_dir": "/tmp/%(self_name)s",
+    "state_base_dir": "/var/lib/%(self_name)s",
+    "state_files_dir": "%(state_base_dir)s/state",
+    "state_file_retention": "50",
+    "state_file_name_prefix": "state-",
+    "state_file_name_suffix": ".log"
+}
+config = ConfigParser(defaults=internal_defaults)
 config.read(CONST.CFG_DEFAULT_FILENAME)
 
 
-def validate_config_defaults(config_obj: configparser.ConfigParser()) -> None:
+def print_section_header(header: str) -> str:
+    return f"Loading config section '[{header}]' ..."
+
+
+def validate_default_section(config_obj: configparser.ConfigParser()) -> None:
     log.debug(f"Loading config from file '{CONST.CFG_DEFAULT_ABS_PATH}' ...")
     if not config_obj.sections():
         log.error(f"No config sections found in '{CONST.CFG_DEFAULT_ABS_PATH}'. Exiting 1 ...")
         sys.exit(1)
     if config.defaults():
+        log.debug(f"Symbol legend:\n"
+                  f"* Global default from section '[{config_obj.default_section}]'\n"
+                  f"~ Local option, doesn't exist in '[{config_obj.default_section}]'\n"
+                  f"+ Local override of a value from '[{config_obj.default_section}]'\n"
+                  f"= Local override, same value as in '[{config_obj.default_section}]'")
+        log.debug(print_section_header(config_obj.default_section))
         for default in config_obj.defaults():
-            log.debug(f"    {default} = {config_obj[config_obj.default_section][default]}")
+            ini_defaults.append({default: config_obj[config_obj.default_section][default]})
+            log.debug(f"* {default} = {config_obj[config_obj.default_section][default]}")
     else:
         log.debug(f"No defaults defined")
 
@@ -57,22 +94,32 @@ def config_has_valid_section(config_obj: configparser.ConfigParser()) -> bool:
     return has_valid_section
 
 
-#def option_has_default_value(config_option: configparser.ConfigParser(), section: str) -> bool:
-#
-#~ local option that doesn't exist in defaults section
-#+ local option that overrides a default
-#* global option
+def is_default(config_key: str) -> bool:
+    return any(config_key in ini_default for ini_default in ini_defaults)
+
+
+def is_same_as_default(config_kv_pair: dict) -> bool:
+    return config_kv_pair in ini_defaults
+
 
 def validate_config_sections(config_obj: configparser.ConfigParser()) -> None:
     for section in config_obj.sections():
-        log.debug(f"Loading config '[{section}]' ...")
-        for key in config_obj[section]:
-            # log.debug(config_obj.has_option(section, key))
-            is_local_option = True if config_obj.has_option(section, key) else False
-            log.debug(f"""    {key}{"/" if is_local_option else ".."} = {config_obj[section][key]}""")
+        log.debug(print_section_header(section))
+        if CONST.CFG_MANDATORY not in config_obj.options(section, no_defaults=True):
+            log.warning(f"Config section '[{section}]' does not have mandatory option '{CONST.CFG_MANDATORY}' set, "
+                        f"skipping section ...")
+            config_obj.remove_section(section)
+        else:
+            for key in config_obj.options(section, no_defaults=True):
+                kv_prefix = "~"
+                if is_default(key):
+                    kv_prefix = "+"
+                    if is_same_as_default({key: config_obj[section][key]}):
+                        kv_prefix = "="
+                log.debug(f"{kv_prefix} {key} = {config_obj[section][key]}")
 
 
-validate_config_defaults(config)
+validate_default_section(config)
 if config_has_valid_section(config):
     validate_config_sections(config)
 else:
@@ -80,10 +127,9 @@ else:
               f"option set. Exiting 2 ...")
     sys.exit(2)
 
-
-# https://stackoverflow.com/a/2451872
 quit()
 
+
 # This is a sample Python script.
 
 # Press Umschalt+F10 to execute it or replace it with your code.