diff --git a/nova/flags.py b/nova/flags.py
index f35f5fa1..b3bdd088 100644
--- a/nova/flags.py
+++ b/nova/flags.py
@@ -21,16 +21,145 @@ Package-level global flags are defined here, the rest are defined
 where they're used.
 """
 
+import getopt
 import socket
+import sys
+
+import gflags
 
 
-from gflags import *
+class FlagValues(gflags.FlagValues):
+    """Extension of gflags.FlagValues that allows undefined and runtime flags.
+
+    Unknown flags will be ignored when parsing the command line, but the
+    command line will be kept so that it can be replayed if new flags are
+    defined after the initial parsing.
+    
+    """
+
+    def __init__(self):
+        gflags.FlagValues.__init__(self)
+        self.__dict__['__dirty'] = []
+        self.__dict__['__was_already_parsed'] = False
+        self.__dict__['__stored_argv'] = []
+
+    def __call__(self, argv):
+        # We're doing some hacky stuff here so that we don't have to copy
+        # out all the code of the original verbatim and then tweak a few lines.
+        # We're hijacking the output of getopt so we can still return the
+        # leftover args at the end
+        sneaky_unparsed_args = {"value": None}
+        original_argv = list(argv)
+        
+        if self.IsGnuGetOpt():
+            orig_getopt = getattr(getopt, 'gnu_getopt')
+            orig_name = 'gnu_getopt'
+        else:
+            orig_getopt = getattr(getopt, 'getopt')
+            orig_name = 'getopt'
+
+        def _sneaky(*args, **kw):
+            optlist, unparsed_args = orig_getopt(*args, **kw)
+            sneaky_unparsed_args['value'] = unparsed_args
+            return optlist, unparsed_args
+
+        try:
+            setattr(getopt, orig_name, _sneaky)
+            args = gflags.FlagValues.__call__(self, argv)
+        except gflags.UnrecognizedFlagError:
+            # Undefined args were found, for now we don't care so just
+            # act like everything went well
+            # (these three lines are copied pretty much verbatim from the end
+            # of the __call__ function we are wrapping)
+            unparsed_args = sneaky_unparsed_args['value']
+            if unparsed_args:
+                if self.IsGnuGetOpt():
+                    args = argv[:1] + unparsed
+                else:
+                    args = argv[:1] + original_argv[-len(unparsed_args):]
+            else:
+                args = argv[:1]
+        finally:
+            setattr(getopt, orig_name, orig_getopt)
+        
+        # Store the arguments for later, we'll need them for new flags
+        # added at runtime
+        self.__dict__['__stored_argv'] = original_argv
+        self.__dict__['__was_already_parsed'] = True
+        self.ClearDirty()
+        return args
+
+    def SetDirty(self, name):
+        """Mark a flag as dirty so that accessing it will case a reparse."""
+        self.__dict__['__dirty'].append(name)
+    
+    def IsDirty(self, name):
+        return name in self.__dict__['__dirty']
+
+    def ClearDirty(self):
+        self.__dict__['__is_dirty'] = []
+
+    def WasAlreadyParsed(self):
+        return self.__dict__['__was_already_parsed']
+
+    def ParseNewFlags(self):
+        if '__stored_argv' not in self.__dict__:
+            return
+        new_flags = FlagValues()
+        for k in self.__dict__['__dirty']:
+            new_flags[k] = gflags.FlagValues.__getitem__(self, k)
+
+        new_flags(self.__dict__['__stored_argv'])
+        for k in self.__dict__['__dirty']:
+            setattr(self, k, getattr(new_flags, k))
+        self.ClearDirty()
+        
+    def __setitem__(self, name, flag):
+        gflags.FlagValues.__setitem__(self, name, flag)
+        if self.WasAlreadyParsed():
+            self.SetDirty(name)
+    
+    def __getitem__(self, name):
+        if self.IsDirty(name):
+            self.ParseNewFlags()
+        return gflags.FlagValues.__getitem__(self, name)
+
+    def __getattr__(self, name):
+        if self.IsDirty(name):
+            self.ParseNewFlags()
+        return gflags.FlagValues.__getattr__(self, name)
+
+
+FLAGS = FlagValues()
+
+
+def _wrapper(func):
+    def _wrapped(*args, **kw):
+        kw.setdefault('flag_values', FLAGS)
+        func(*args, **kw)
+    _wrapped.func_name = func.func_name
+    return _wrapped
+
+
+DEFINE_string = _wrapper(gflags.DEFINE_string)
+DEFINE_integer = _wrapper(gflags.DEFINE_integer)
+DEFINE_bool = _wrapper(gflags.DEFINE_bool)
+DEFINE_boolean = _wrapper(gflags.DEFINE_boolean)
+DEFINE_float = _wrapper(gflags.DEFINE_float)
+DEFINE_enum = _wrapper(gflags.DEFINE_enum)
+DEFINE_list = _wrapper(gflags.DEFINE_list)
+DEFINE_spaceseplist = _wrapper(gflags.DEFINE_spaceseplist)
+DEFINE_multistring = _wrapper(gflags.DEFINE_multistring)
+DEFINE_multi_int = _wrapper(gflags.DEFINE_multi_int)
+
+
+def DECLARE(name, module_string, flag_values=FLAGS):
+    if module_string not in sys.modules:
+        __import__(module_string, globals(), locals())
+    if name not in flag_values:
+        raise gflags.UnrecognizedFlag(
+                "%s not defined by %s" % (name, module_string))
 
-# This keeps pylint from barfing on the imports
-FLAGS = FLAGS
-DEFINE_string = DEFINE_string
-DEFINE_integer = DEFINE_integer
-DEFINE_bool = DEFINE_bool
 
 # __GLOBAL FLAGS ONLY__
 # Define any app-specific flags in their own files, docs at:
diff --git a/nova/tests/declare_flags.py b/nova/tests/declare_flags.py
new file mode 100644
index 00000000..51a55ec7
--- /dev/null
+++ b/nova/tests/declare_flags.py
@@ -0,0 +1,23 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, 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.
+
+from nova import flags
+
+FLAGS = flags.FLAGS
+
+flags.DEFINE_integer('answer', 42, 'test flag')
diff --git a/nova/tests/flags_unittest.py b/nova/tests/flags_unittest.py
new file mode 100644
index 00000000..d49d5dc4
--- /dev/null
+++ b/nova/tests/flags_unittest.py
@@ -0,0 +1,87 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, 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.
+
+from nova import exception
+from nova import flags
+from nova import test
+
+
+class FlagsTestCase(test.TrialTestCase):
+    def setUp(self):
+        super(FlagsTestCase, self).setUp()
+        self.FLAGS = flags.FlagValues()
+        self.global_FLAGS = flags.FLAGS
+
+    def test_define(self):
+        self.assert_('string' not in self.FLAGS)
+        self.assert_('int' not in self.FLAGS)
+        self.assert_('false' not in self.FLAGS)
+        self.assert_('true' not in self.FLAGS)
+
+        flags.DEFINE_string('string', 'default', 'desc', flag_values=self.FLAGS)
+        flags.DEFINE_integer('int', 1, 'desc', flag_values=self.FLAGS)
+        flags.DEFINE_bool('false', False, 'desc', flag_values=self.FLAGS)
+        flags.DEFINE_bool('true', True, 'desc', flag_values=self.FLAGS)
+
+        self.assert_(self.FLAGS['string'])
+        self.assert_(self.FLAGS['int'])
+        self.assert_(self.FLAGS['false'])
+        self.assert_(self.FLAGS['true'])
+        self.assertEqual(self.FLAGS.string, 'default')
+        self.assertEqual(self.FLAGS.int, 1)
+        self.assertEqual(self.FLAGS.false, False)
+        self.assertEqual(self.FLAGS.true, True)
+
+        argv = ['flags_test',
+                '--string', 'foo',
+                '--int', '2',
+                '--false',
+                '--notrue']
+
+        self.FLAGS(argv)
+        self.assertEqual(self.FLAGS.string, 'foo')
+        self.assertEqual(self.FLAGS.int, 2)
+        self.assertEqual(self.FLAGS.false, True)
+        self.assertEqual(self.FLAGS.true, False)
+
+    def test_declare(self):
+        self.assert_('answer' not in self.global_FLAGS)
+        flags.DECLARE('answer', 'nova.tests.declare_flags')
+        self.assert_('answer' in self.global_FLAGS)
+        self.assertEqual(self.global_FLAGS.answer, 42)
+
+        # Make sure we don't overwrite anything
+        self.global_FLAGS.answer = 256
+        self.assertEqual(self.global_FLAGS.answer, 256)
+        flags.DECLARE('answer', 'nova.tests.declare_flags')
+        self.assertEqual(self.global_FLAGS.answer, 256)
+
+    def test_runtime_and_unknown_flags(self):
+        self.assert_('runtime_answer' not in self.global_FLAGS)
+
+        argv = ['flags_test', '--runtime_answer=60', 'extra_arg']
+        args = self.global_FLAGS(argv)
+        self.assertEqual(len(args), 2)
+        self.assertEqual(args[1], 'extra_arg')
+
+        self.assert_('runtime_answer' not in self.global_FLAGS)
+
+        import nova.tests.runtime_flags
+
+        self.assert_('runtime_answer' in self.global_FLAGS)
+        self.assertEqual(self.global_FLAGS.runtime_answer, 60)
diff --git a/nova/tests/runtime_flags.py b/nova/tests/runtime_flags.py
new file mode 100644
index 00000000..1eb50140
--- /dev/null
+++ b/nova/tests/runtime_flags.py
@@ -0,0 +1,23 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, 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.
+
+from nova import flags
+
+FLAGS = flags.FLAGS
+
+flags.DEFINE_integer('runtime_answer', 54, 'test flag')
diff --git a/run_tests.py b/run_tests.py
index f6208825..7fe6e73e 100644
--- a/run_tests.py
+++ b/run_tests.py
@@ -54,6 +54,7 @@ from nova.tests.auth_unittest import *
 from nova.tests.api_unittest import *
 from nova.tests.cloud_unittest import *
 from nova.tests.compute_unittest import *
+from nova.tests.flags_unittest import *
 from nova.tests.model_unittest import *
 from nova.tests.network_unittest import *
 from nova.tests.objectstore_unittest import *