diff --git a/lib/runtime.py b/lib/runtime.py
index 2d65ef0baa185b3904638b59d0668bc191b59dc1..4d5e3efc624861e138c08e393c4c0febbd26f540 100644
--- a/lib/runtime.py
+++ b/lib/runtime.py
@@ -28,6 +28,7 @@ import threading
 
 from ganeti import constants
 from ganeti import errors
+from ganeti import utils
 
 
 _priv = None
@@ -91,11 +92,79 @@ class GetentResolver:
     self.rapi_gid = GetGid(constants.RAPI_GROUP, _getgrnam)
 
     self.noded_uid = GetUid(constants.NODED_USER, _getpwnam)
+    self.noded_gid = GetGid(constants.NODED_GROUP, _getgrnam)
 
     # Misc Ganeti groups
     self.daemons_gid = GetGid(constants.DAEMONS_GROUP, _getgrnam)
     self.admin_gid = GetGid(constants.ADMIN_GROUP, _getgrnam)
 
+    self._uid2user = {
+      self.masterd_uid: constants.MASTERD_USER,
+      self.confd_uid: constants.CONFD_USER,
+      self.rapi_uid: constants.RAPI_USER,
+      self.noded_uid: constants.NODED_USER,
+      }
+
+    self._gid2group = {
+      self.masterd_gid: constants.MASTERD_GROUP,
+      self.confd_gid: constants.CONFD_GROUP,
+      self.rapi_gid: constants.RAPI_GROUP,
+      self.noded_gid: constants.NODED_GROUP,
+      self.daemons_gid: constants.DAEMONS_GROUP,
+      self.admin_gid: constants.ADMIN_GROUP,
+      }
+
+    self._user2uid = utils.InvertDict(self._uid2user)
+    self._group2gid = utils.InvertDict(self._gid2group)
+
+  def LookupUid(self, uid):
+    """Looks which Ganeti user belongs to this uid.
+
+    @param uid: The uid to lookup
+    @returns The user name associated with that uid
+
+    """
+    try:
+      return self._uid2user[uid]
+    except KeyError:
+      raise errors.ConfigurationError("Unknown Ganeti uid '%d'" % uid)
+
+  def LookupGid(self, gid):
+    """Looks which Ganeti group belongs to this gid.
+
+    @param gid: The gid to lookup
+    @returns The group name associated with that gid
+
+    """
+    try:
+      return self._gid2group[gid]
+    except KeyError:
+      raise errors.ConfigurationError("Unknown Ganeti gid '%d'" % gid)
+
+  def LookupUser(self, name):
+    """Looks which uid belongs to this name.
+
+    @param name: The name to lookup
+    @returns The uid associated with that user name
+
+    """
+    try:
+      return self._user2uid[name]
+    except KeyError:
+      raise errors.ConfigurationError("Unknown Ganeti user '%s'" % name)
+
+  def LookupGroup(self, name):
+    """Looks which gid belongs to this name.
+
+    @param name: The name to lookup
+    @returns The gid associated with that group name
+
+    """
+    try:
+      return self._group2gid[name]
+    except KeyError:
+      raise errors.ConfigurationError("Unknown Ganeti group '%s'" % name)
+
 
 def GetEnts(resolver=GetentResolver):
   """Singleton wrapper around resolver instance.
diff --git a/test/ganeti.runtime_unittest.py b/test/ganeti.runtime_unittest.py
index 3ba9ac873b68b20f2c1d0c3bb26f7c01128d194d..79ede58bc71730c96af7208cbf82173cd3f4257e 100755
--- a/test/ganeti.runtime_unittest.py
+++ b/test/ganeti.runtime_unittest.py
@@ -25,6 +25,7 @@ from ganeti import errors
 from ganeti import runtime
 
 import testutils
+import unittest
 
 
 class _EntStub:
@@ -50,6 +51,7 @@ def _StubGetgrnam(group):
     constants.RAPI_GROUP: _EntStub(gid=2),
     constants.DAEMONS_GROUP: _EntStub(gid=3),
     constants.ADMIN_GROUP: _EntStub(gid=4),
+    constants.NODED_GROUP: _EntStub(gid=5),
     }
   return groups[group]
 
@@ -67,29 +69,30 @@ class ResolverStubRaising(object):
     raise errors.ConfigurationError("No entries")
 
 
-class TestErrors(testutils.GanetiTestCase):
-  def testEverythingSuccessful(self):
-    resolver = runtime.GetentResolver(_getpwnam=_StubGetpwnam,
-                                      _getgrnam=_StubGetgrnam)
+class TestErrors(unittest.TestCase):
+  def setUp(self):
+    self.resolver = runtime.GetentResolver(_getpwnam=_StubGetpwnam,
+                                           _getgrnam=_StubGetgrnam)
 
-    self.assertEqual(resolver.masterd_uid,
+  def testEverythingSuccessful(self):
+    self.assertEqual(self.resolver.masterd_uid,
                      _StubGetpwnam(constants.MASTERD_USER).pw_uid)
-    self.assertEqual(resolver.masterd_gid,
+    self.assertEqual(self.resolver.masterd_gid,
                      _StubGetgrnam(constants.MASTERD_GROUP).gr_gid)
-    self.assertEqual(resolver.confd_uid,
+    self.assertEqual(self.resolver.confd_uid,
                      _StubGetpwnam(constants.CONFD_USER).pw_uid)
-    self.assertEqual(resolver.confd_gid,
+    self.assertEqual(self.resolver.confd_gid,
                      _StubGetgrnam(constants.CONFD_GROUP).gr_gid)
-    self.assertEqual(resolver.rapi_uid,
+    self.assertEqual(self.resolver.rapi_uid,
                      _StubGetpwnam(constants.RAPI_USER).pw_uid)
-    self.assertEqual(resolver.rapi_gid,
+    self.assertEqual(self.resolver.rapi_gid,
                      _StubGetgrnam(constants.RAPI_GROUP).gr_gid)
-    self.assertEqual(resolver.noded_uid,
+    self.assertEqual(self.resolver.noded_uid,
                      _StubGetpwnam(constants.NODED_USER).pw_uid)
 
-    self.assertEqual(resolver.daemons_gid,
+    self.assertEqual(self.resolver.daemons_gid,
                      _StubGetgrnam(constants.DAEMONS_GROUP).gr_gid)
-    self.assertEqual(resolver.admin_gid,
+    self.assertEqual(self.resolver.admin_gid,
                      _StubGetgrnam(constants.ADMIN_GROUP).gr_gid)
 
   def testUserNotFound(self):
@@ -104,6 +107,36 @@ class TestErrors(testutils.GanetiTestCase):
     self.assertRaises(errors.ConfigurationError, runtime.GetEnts,
                       resolver=ResolverStubRaising)
 
+  def testLookupForUser(self):
+    master_stub = _StubGetpwnam(constants.MASTERD_USER)
+    rapi_stub = _StubGetpwnam(constants.RAPI_USER)
+    self.assertEqual(self.resolver.LookupUid(master_stub.pw_uid),
+                     constants.MASTERD_USER)
+    self.assertEqual(self.resolver.LookupUid(rapi_stub.pw_uid),
+                     constants.RAPI_USER)
+    self.assertEqual(self.resolver.LookupUser(constants.MASTERD_USER),
+                     master_stub.pw_uid)
+    self.assertEqual(self.resolver.LookupUser(constants.RAPI_USER),
+                     rapi_stub.pw_uid)
+
+  def testLookupForGroup(self):
+    master_stub = _StubGetgrnam(constants.MASTERD_GROUP)
+    rapi_stub = _StubGetgrnam(constants.RAPI_GROUP)
+    self.assertEqual(self.resolver.LookupGid(master_stub.gr_gid),
+                     constants.MASTERD_GROUP)
+    self.assertEqual(self.resolver.LookupGid(rapi_stub.gr_gid),
+                     constants.RAPI_GROUP)
+
+  def testLookupForUserNotFound(self):
+    self.assertRaises(errors.ConfigurationError, self.resolver.LookupUid, 9999)
+    self.assertRaises(errors.ConfigurationError,
+                      self.resolver.LookupUser, "does-not-exist-foo")
+
+  def testLookupForGroupNotFound(self):
+    self.assertRaises(errors.ConfigurationError, self.resolver.LookupGid, 9999)
+    self.assertRaises(errors.ConfigurationError,
+                      self.resolver.LookupGroup, "does-not-exist-foo")
+
 
 if __name__ == "__main__":
   testutils.GanetiTestProgram()