diff --git a/changelog.d/4315.feature b/changelog.d/4315.feature
new file mode 100644
index 000000000000..23e82fd02d93
--- /dev/null
+++ b/changelog.d/4315.feature
@@ -0,0 +1 @@
+Add a script to generate a clean config file
diff --git a/scripts/generate_config b/scripts/generate_config
new file mode 100755
index 000000000000..61c5f049e8aa
--- /dev/null
+++ b/scripts/generate_config
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+
+import argparse
+import sys
+
+from synapse.config.homeserver import HomeServerConfig
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--config-dir",
+        default="CONFDIR",
+
+        help="The path where the config files are kept. Used to create filenames for "
+             "things like the log config and the signing key. Default: %(default)s",
+    )
+
+    parser.add_argument(
+        "--data-dir",
+        default="DATADIR",
+        help="The path where the data files are kept. Used to create filenames for "
+             "things like the database and media store. Default: %(default)s",
+    )
+
+    parser.add_argument(
+        "--server-name",
+        default="SERVERNAME",
+        help="The server name. Used to initialise the server_name config param, but also "
+             "used in the names of some of the config files. Default: %(default)s",
+    )
+
+    parser.add_argument(
+        "--report-stats",
+        action="store",
+        help="Whether the generated config reports anonymized usage statistics",
+        choices=["yes", "no"],
+    )
+
+    parser.add_argument(
+        "--generate-secrets",
+        action="store_true",
+        help="Enable generation of new secrets for things like the macaroon_secret_key."
+             "By default, these parameters will be left unset."
+    )
+
+    parser.add_argument(
+        "-o", "--output-file",
+        type=argparse.FileType('w'),
+        default=sys.stdout,
+        help="File to write the configuration to. Default: stdout",
+    )
+
+    args = parser.parse_args()
+
+    report_stats = args.report_stats
+    if report_stats is not None:
+        report_stats = report_stats == "yes"
+
+    conf = HomeServerConfig().generate_config(
+        config_dir_path=args.config_dir,
+        data_dir_path=args.data_dir,
+        server_name=args.server_name,
+        generate_secrets=args.generate_secrets,
+        report_stats=report_stats,
+    )
+
+    args.output_file.write(conf)
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 14dae65ea078..fd2d6d52efee 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -134,10 +134,6 @@ def read_file(cls, file_path, config_name):
         with open(file_path) as file_stream:
             return file_stream.read()
 
-    @staticmethod
-    def default_path(name):
-        return os.path.abspath(os.path.join(os.path.curdir, name))
-
     @staticmethod
     def read_config_file(file_path):
         with open(file_path) as file_stream:
@@ -151,8 +147,39 @@ def invoke_all(self, name, *args, **kargs):
         return results
 
     def generate_config(
-        self, config_dir_path, server_name, is_generating_file, report_stats=None
+        self,
+        config_dir_path,
+        data_dir_path,
+        server_name,
+        generate_secrets=False,
+        report_stats=None,
     ):
+        """Build a default configuration file
+
+        This is used both when the user explicitly asks us to generate a config file
+        (eg with --generate_config), and before loading the config at runtime (to give
+        a base which the config files override)
+
+        Args:
+            config_dir_path (str): The path where the config files are kept. Used to
+                create filenames for things like the log config and the signing key.
+
+            data_dir_path (str): The path where the data files are kept. Used to create
+                filenames for things like the database and media store.
+
+            server_name (str): The server name. Used to initialise the server_name
+                config param, but also used in the names of some of the config files.
+
+            generate_secrets (bool): True if we should generate new secrets for things
+                like the macaroon_secret_key. If False, these parameters will be left
+                unset.
+
+            report_stats (bool|None): Initial setting for the report_stats setting.
+                If None, report_stats will be left unset.
+
+        Returns:
+            str: the yaml config file
+        """
         default_config = "# vim:ft=yaml\n"
 
         default_config += "\n\n".join(
@@ -160,15 +187,14 @@ def generate_config(
             for conf in self.invoke_all(
                 "default_config",
                 config_dir_path=config_dir_path,
+                data_dir_path=data_dir_path,
                 server_name=server_name,
-                is_generating_file=is_generating_file,
+                generate_secrets=generate_secrets,
                 report_stats=report_stats,
             )
         )
 
-        config = yaml.load(default_config)
-
-        return default_config, config
+        return default_config
 
     @classmethod
     def load_config(cls, description, argv):
@@ -274,12 +300,14 @@ def load_or_generate_config(cls, description, argv):
                 if not cls.path_exists(config_dir_path):
                     os.makedirs(config_dir_path)
                 with open(config_path, "w") as config_file:
-                    config_str, config = obj.generate_config(
+                    config_str = obj.generate_config(
                         config_dir_path=config_dir_path,
+                        data_dir_path=os.getcwd(),
                         server_name=server_name,
                         report_stats=(config_args.report_stats == "yes"),
-                        is_generating_file=True,
+                        generate_secrets=True,
                     )
+                    config = yaml.load(config_str)
                     obj.invoke_all("generate_files", config)
                     config_file.write(config_str)
                 print(
@@ -350,11 +378,13 @@ def read_config_files(self, config_files, keys_directory=None, generate_keys=Fal
             raise ConfigError(MISSING_SERVER_NAME)
 
         server_name = specified_config["server_name"]
-        _, config = self.generate_config(
+        config_string = self.generate_config(
             config_dir_path=config_dir_path,
+            data_dir_path=os.getcwd(),
             server_name=server_name,
-            is_generating_file=False,
+            generate_secrets=False,
         )
+        config = yaml.load(config_string)
         config.pop("log_config")
         config.update(specified_config)
 
diff --git a/synapse/config/database.py b/synapse/config/database.py
index e915d9d09b01..c8890147a648 100644
--- a/synapse/config/database.py
+++ b/synapse/config/database.py
@@ -12,6 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import os
 
 from ._base import Config
 
@@ -45,8 +46,8 @@ def read_config(self, config):
 
         self.set_databasepath(config.get("database_path"))
 
-    def default_config(self, **kwargs):
-        database_path = self.abspath("homeserver.db")
+    def default_config(self, data_dir_path, **kwargs):
+        database_path = os.path.join(data_dir_path, "homeserver.db")
         return """\
         # Database configuration
         database:
diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index 9d740c7a71f2..5aad062c36ac 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -53,10 +53,3 @@ class HomeServerConfig(TlsConfig, ServerConfig, DatabaseConfig, LoggingConfig,
                        ServerNoticesConfig, RoomDirectoryConfig,
                        ):
     pass
-
-
-if __name__ == '__main__':
-    import sys
-    sys.stdout.write(
-        HomeServerConfig().generate_config(sys.argv[1], sys.argv[2], True)[0]
-    )
diff --git a/synapse/config/key.py b/synapse/config/key.py
index 279c47bb48ad..53f48fe2dd91 100644
--- a/synapse/config/key.py
+++ b/synapse/config/key.py
@@ -66,26 +66,35 @@ def read_config(self, config):
         # falsification of values
         self.form_secret = config.get("form_secret", None)
 
-    def default_config(self, config_dir_path, server_name, is_generating_file=False,
+    def default_config(self, config_dir_path, server_name, generate_secrets=False,
                        **kwargs):
         base_key_name = os.path.join(config_dir_path, server_name)
 
-        if is_generating_file:
-            macaroon_secret_key = random_string_with_symbols(50)
-            form_secret = '"%s"' % random_string_with_symbols(50)
+        if generate_secrets:
+            macaroon_secret_key = 'macaroon_secret_key: "%s"' % (
+                random_string_with_symbols(50),
+            )
+            form_secret = 'form_secret: "%s"' % random_string_with_symbols(50)
         else:
-            macaroon_secret_key = None
-            form_secret = 'null'
+            macaroon_secret_key = "# macaroon_secret_key: <PRIVATE STRING>"
+            form_secret = "# form_secret: <PRIVATE STRING>"
 
         return """\
-        macaroon_secret_key: "%(macaroon_secret_key)s"
+        # a secret which is used to sign access tokens. If none is specified,
+        # the registration_shared_secret is used, if one is given; otherwise,
+        # a secret key is derived from the signing key.
+        #
+        # Note that changing this will invalidate any active access tokens, so
+        # all clients will have to log back in.
+        %(macaroon_secret_key)s
 
         # Used to enable access token expiration.
         expire_access_token: False
 
         # a secret which is used to calculate HMACs for form values, to stop
-        # falsification of values
-        form_secret: %(form_secret)s
+        # falsification of values. Must be specified for the User Consent
+        # forms to work.
+        %(form_secret)s
 
         ## Signing Keys ##
 
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index 7081868963d4..f87efecbf8f6 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -80,9 +80,7 @@ def read_config(self, config):
         self.log_file = self.abspath(config.get("log_file"))
 
     def default_config(self, config_dir_path, server_name, **kwargs):
-        log_config = self.abspath(
-            os.path.join(config_dir_path, server_name + ".log.config")
-        )
+        log_config = os.path.join(config_dir_path, server_name + ".log.config")
         return """
         # A yaml python logging config file
         log_config: "%(log_config)s"
diff --git a/synapse/config/metrics.py b/synapse/config/metrics.py
index 61155c99d057..718c43ae0395 100644
--- a/synapse/config/metrics.py
+++ b/synapse/config/metrics.py
@@ -24,10 +24,16 @@ def read_config(self, config):
         self.metrics_bind_host = config.get("metrics_bind_host", "127.0.0.1")
 
     def default_config(self, report_stats=None, **kwargs):
-        suffix = "" if report_stats is None else "report_stats: %(report_stats)s\n"
-        return ("""\
+        res = """\
         ## Metrics ###
 
         # Enable collection and rendering of performance metrics
         enable_metrics: False
-        """ + suffix) % locals()
+        """
+
+        if report_stats is None:
+            res += "# report_stats: true|false\n"
+        else:
+            res += "report_stats: %s\n" % ('true' if report_stats else 'false')
+
+        return res
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index e365f0c30b3d..6c2b543b8cdf 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -50,8 +50,13 @@ def read_config(self, config):
                 raise ConfigError('Invalid auto_join_rooms entry %s' % (room_alias,))
         self.autocreate_auto_join_rooms = config.get("autocreate_auto_join_rooms", True)
 
-    def default_config(self, **kwargs):
-        registration_shared_secret = random_string_with_symbols(50)
+    def default_config(self, generate_secrets=False, **kwargs):
+        if generate_secrets:
+            registration_shared_secret = 'registration_shared_secret: "%s"' % (
+                random_string_with_symbols(50),
+            )
+        else:
+            registration_shared_secret = '# registration_shared_secret: <PRIVATE STRING>'
 
         return """\
         ## Registration ##
@@ -78,7 +83,7 @@ def default_config(self, **kwargs):
 
         # If set, allows registration by anyone who also has the shared
         # secret, even if registration is otherwise disabled.
-        registration_shared_secret: "%(registration_shared_secret)s"
+        %(registration_shared_secret)s
 
         # Set the number of bcrypt rounds used to generate password hash.
         # Larger numbers increase the work factor needed to generate the hash.
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 06c62ab62c0b..76e3340a9146 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -12,7 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
+import os
 from collections import namedtuple
 
 from synapse.util.module_loader import load_module
@@ -175,9 +175,9 @@ def read_config(self, config):
                 "url_preview_url_blacklist", ()
             )
 
-    def default_config(self, **kwargs):
-        media_store = self.default_path("media_store")
-        uploads_path = self.default_path("uploads")
+    def default_config(self, data_dir_path, **kwargs):
+        media_store = os.path.join(data_dir_path, "media_store")
+        uploads_path = os.path.join(data_dir_path, "uploads")
         return r"""
         # Directory where uploaded images and attachments are stored.
         media_store_path: "%(media_store)s"
diff --git a/synapse/config/server.py b/synapse/config/server.py
index a9154ad462bb..2bc406df1488 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import logging
+import os.path
 
 from synapse.http.endpoint import parse_and_validate_server_name
 
@@ -203,7 +204,7 @@ def read_config(self, config):
                 ]
             })
 
-    def default_config(self, server_name, **kwargs):
+    def default_config(self, server_name, data_dir_path, **kwargs):
         _, bind_port = parse_and_validate_server_name(server_name)
         if bind_port is not None:
             unsecure_port = bind_port - 400
@@ -211,7 +212,7 @@ def default_config(self, server_name, **kwargs):
             bind_port = 8448
             unsecure_port = 8008
 
-        pid_file = self.abspath("homeserver.pid")
+        pid_file = os.path.join(data_dir_path, "homeserver.pid")
         return """\
         ## Server ##