diff --git a/aos/configuration.cc b/aos/configuration.cc
index 94606ec..a1cc614 100644
--- a/aos/configuration.cc
+++ b/aos/configuration.cc
@@ -8,11 +8,59 @@
 #include <ifaddrs.h>
 #include <unistd.h>
 
-#include "aos/logging/logging.h"
-#include "aos/unique_malloc_ptr.h"
+#include "absl/container/btree_set.h"
+#include "absl/strings/string_view.h"
+#include "aos/configuration_generated.h"
+#include "aos/flatbuffer_merge.h"
+#include "aos/json_to_flatbuffer.h"
 #include "aos/once.h"
+#include "aos/unique_malloc_ptr.h"
+#include "aos/util/file.h"
+#include "glog/logging.h"
 
 namespace aos {
+
+// Define the compare and equal operators for Location and Application so we can
+// insert them in the btree below.
+//
+// These are not in headers because they are only comparing part of the
+// flatbuffer, and it seems weird to expose that as *the* compare operator.  And
+// I can't put them in an anonymous namespace because they wouldn't be found
+// that way by the btree.
+bool operator<(const Flatbuffer<Location> &lhs,
+               const Flatbuffer<Location> &rhs) {
+  int name_compare = lhs.message().name()->string_view().compare(
+      rhs.message().name()->string_view());
+  if (name_compare == 0) {
+    return lhs.message().type()->string_view() <
+           rhs.message().type()->string_view();
+  } else if (name_compare < 0) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+bool operator==(const Flatbuffer<Location> &lhs,
+                const Flatbuffer<Location> &rhs) {
+  return lhs.message().name()->string_view() ==
+             rhs.message().name()->string_view() &&
+         lhs.message().type()->string_view() ==
+             rhs.message().type()->string_view();
+}
+
+bool operator==(const Flatbuffer<Application> &lhs,
+                const Flatbuffer<Application> &rhs) {
+  return lhs.message().name()->string_view() ==
+         rhs.message().name()->string_view();
+}
+
+bool operator<(const Flatbuffer<Application> &lhs,
+               const Flatbuffer<Application> &rhs) {
+  return lhs.message().name()->string_view() <
+         rhs.message().name()->string_view();
+}
+
 namespace configuration {
 namespace {
 
@@ -23,21 +71,21 @@
   static const char *kOverrideVariable = "FRC971_IP_OVERRIDE";
   const char *override_ip = getenv(kOverrideVariable);
   if (override_ip != NULL) {
-    LOG(INFO, "Override IP is %s\n", override_ip);
+    LOG(INFO) << "Override IP is " << override_ip;
     static in_addr r;
     if (inet_aton(override_ip, &r) != 0) {
       return &r;
     } else {
-      LOG(WARNING, "error parsing %s value '%s'\n",
-          kOverrideVariable, override_ip);
+      LOG(WARNING) << "error parsing " << kOverrideVariable << " value '"
+                   << override_ip << "'";
     }
   } else {
-    LOG(INFO, "Couldn't get environmental variable.\n");
+    LOG(INFO) << "Couldn't get environmental variable.";
   }
 
   ifaddrs *addrs;
   if (getifaddrs(&addrs) != 0) {
-    PLOG(FATAL, "getifaddrs(%p) failed", &addrs);
+    PLOG(FATAL) << "getifaddrs(" << &addrs << ") failed";
   }
   // Smart pointers don't work very well for iterating through a linked list,
   // but it does do a very nice job of making sure that addrs gets freed.
@@ -54,8 +102,9 @@
       }
     }
   }
-  LOG(FATAL, "couldn't find an AF_INET interface named \"%s\"\n",
-      kLinuxNetInterface);
+  LOG(FATAL) << "couldn't find an AF_INET interface named \""
+             << kLinuxNetInterface << "\"";
+  return nullptr;
 }
 
 const char *DoGetRootDirectory() {
@@ -69,18 +118,19 @@
     ssize_t ret = readlink("/proc/self/exe", r, size);
     if (ret < 0) {
       if (ret != -1) {
-        LOG(WARNING, "it returned %zd, not -1\n", ret);
+        LOG(WARNING) << "it returned " << ret << ", not -1";
       }
-      PLOG(FATAL, "readlink(\"/proc/self/exe\", %p, %zu) failed", r, size);
+      PLOG(FATAL) << "readlink(\"/proc/self/exe\", " << r << ", " << size
+                  << ") failed";
     }
     if (ret < size) {
       void *last_slash = memrchr(r, '/', ret);
       if (last_slash == NULL) {
         r[ret] = '\0';
-        LOG(FATAL, "couldn't find a '/' in \"%s\"\n", r);
+        LOG(FATAL) << "couldn't find a '/' in \"" << r << "\"";
       }
       *static_cast<char *>(last_slash) = '\0';
-      LOG(INFO, "got a root dir of \"%s\"\n", r);
+      LOG(INFO) << "got a root dir of \"" << r << "\"";
       return r;
     }
   }
@@ -95,6 +145,225 @@
   return r;
 }
 
+// Extracts the folder part of a path.  Returns ./ if there is no path.
+absl::string_view ExtractFolder(const absl::string_view filename) {
+  auto last_slash_pos = filename.find_last_of("/\\");
+
+  return last_slash_pos == absl::string_view::npos
+             ? absl::string_view("./")
+             : filename.substr(0, last_slash_pos + 1);
+}
+
+Flatbuffer<Configuration> ReadConfig(
+    const absl::string_view path, absl::btree_set<std::string> *visited_paths) {
+  Flatbuffer<Configuration> config(JsonToFlatbuffer(
+      util::ReadFileToStringOrDie(path), ConfigurationTypeTable()));
+  // Depth first.  Take the following example:
+  //
+  // config1.json:
+  // {
+  //   "locations": [
+  //     {
+  //       "name": "/foo",
+  //       "type": ".aos.bar",
+  //       "max_size": 5
+  //     }
+  //   ],
+  //   "imports": [
+  //     "config2.json",
+  //   ]
+  // }
+  //
+  // config2.json:
+  // {
+  //   "locations": [
+  //     {
+  //       "name": "/foo",
+  //       "type": ".aos.bar",
+  //       "max_size": 7
+  //     }
+  //   ],
+  // }
+  //
+  // We want the main config (config1.json) to be able to override the imported
+  // config.  That means that it needs to be merged into the imported configs,
+  // not the other way around.
+
+  // Track that we have seen this file before recursing.
+  visited_paths->insert(::std::string(path));
+
+  if (config.message().has_imports()) {
+    // Capture the imports.
+    const flatbuffers::Vector<flatbuffers::Offset<flatbuffers::String>> *v =
+        config.message().imports();
+
+    // And then wipe them.  This gets GCed when we merge later.
+    config.mutable_message()->clear_imports();
+
+    // Start with an empty configuration to merge into.
+    Flatbuffer<Configuration> merged_config =
+        Flatbuffer<Configuration>::Empty();
+
+    const ::std::string folder(ExtractFolder(path));
+
+    for (const flatbuffers::String *str : *v) {
+      const ::std::string included_config = folder + str->c_str();
+      // Abort on any paths we have already seen.
+      CHECK(visited_paths->find(included_config) == visited_paths->end())
+          << ": Found duplicate file " << included_config << " while reading "
+          << path;
+
+      // And them merge everything in.
+      merged_config = MergeFlatBuffers(
+          merged_config, ReadConfig(included_config, visited_paths));
+    }
+
+    // Finally, merge this file in.
+    config = MergeFlatBuffers(merged_config, config);
+  }
+  return config;
+}
+
+// Remove duplicate entries, and handle overrides.
+Flatbuffer<Configuration> MergeConfiguration(
+    const Flatbuffer<Configuration> &config) {
+  // Store all the locations in a sorted set.  This lets us track locations we
+  // have seen before and merge the updates in.
+  absl::btree_set<Flatbuffer<Location>> locations;
+
+  if (config.message().has_locations()) {
+    for (const Location *l : *config.message().locations()) {
+      // Ignore malformed entries.
+      if (!l->has_name()) {
+        continue;
+      }
+      if (!l->has_type()) {
+        continue;
+      }
+
+      // Attempt to insert the location.
+      auto result = locations.insert(CopyFlatBuffer(l));
+      if (!result.second) {
+        // Already there, so merge the new table into the original.
+        *result.first = MergeFlatBuffers(*result.first, CopyFlatBuffer(l));
+      }
+    }
+  }
+
+  // Now repeat this for the application list.
+  absl::btree_set<Flatbuffer<Application>> applications;
+  if (config.message().has_applications()) {
+    for (const Application *a : *config.message().applications()) {
+      if (!a->has_name()) {
+        continue;
+      }
+
+      auto result = applications.insert(CopyFlatBuffer(a));
+      if (!result.second) {
+        *result.first = MergeFlatBuffers(*result.first, CopyFlatBuffer(a));
+      }
+    }
+  }
+
+  flatbuffers::FlatBufferBuilder fbb;
+  fbb.ForceDefaults(1);
+
+  // Start by building the vectors.  They need to come before the final table.
+  // Locations
+  flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Location>>>
+      locations_offset;
+  {
+    ::std::vector<flatbuffers::Offset<Location>> location_offsets;
+    for (const Flatbuffer<Location> &l : locations) {
+      location_offsets.emplace_back(
+          CopyFlatBuffer<Location>(&l.message(), &fbb));
+    }
+    locations_offset = fbb.CreateVector(location_offsets);
+  }
+
+  // Applications
+  flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
+      applications_offset;
+  {
+    ::std::vector<flatbuffers::Offset<Application>> applications_offsets;
+    for (const Flatbuffer<Application> &a : applications) {
+      applications_offsets.emplace_back(
+          CopyFlatBuffer<Application>(&a.message(), &fbb));
+    }
+    applications_offset = fbb.CreateVector(applications_offsets);
+  }
+
+  // Just copy the maps
+  flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Map>>>
+      maps_offset;
+  {
+    ::std::vector<flatbuffers::Offset<Map>> map_offsets;
+    if (config.message().has_maps()) {
+      for (const Map *m : *config.message().maps()) {
+        map_offsets.emplace_back(CopyFlatBuffer<Map>(m, &fbb));
+      }
+      maps_offset = fbb.CreateVector(map_offsets);
+    }
+  }
+
+  // And then build a Configuration with them all.
+  ConfigurationBuilder configuration_builder(fbb);
+  configuration_builder.add_locations(locations_offset);
+  if (config.message().has_maps()) {
+    configuration_builder.add_maps(maps_offset);
+  }
+  configuration_builder.add_applications(applications_offset);
+
+  fbb.Finish(configuration_builder.Finish());
+  return fbb.Release();
+}
+
+// Compares (l < p) a location, and a name, type tuple.
+bool CompareLocations(const Location *l,
+                      ::std::pair<absl::string_view, absl::string_view> p) {
+  int name_compare = l->name()->string_view().compare(p.first);
+  if (name_compare == 0) {
+    return l->type()->string_view() < p.second;
+  } else if (name_compare < 0) {
+    return true;
+  } else {
+    return false;
+  }
+};
+
+// Compares for equality (l == p) a location, and a name, type tuple.
+bool EqualsLocations(const Location *l,
+                     ::std::pair<absl::string_view, absl::string_view> p) {
+  return l->name()->string_view() == p.first &&
+         l->type()->string_view() == p.second;
+}
+
+// Compares (l < p) an application, and a name;
+bool CompareApplications(const Application *a, absl::string_view name) {
+  return a->name()->string_view() < name;
+};
+
+// Compares for equality (l == p) an application, and a name;
+bool EqualsApplications(const Application *a, absl::string_view name) {
+  return a->name()->string_view() == name;
+}
+
+// Maps name for the provided maps.  Modifies name.
+void HandleMaps(const flatbuffers::Vector<flatbuffers::Offset<aos::Map>> *maps,
+                absl::string_view *name) {
+  // For the same reason we merge configs in reverse order, we want to process
+  // maps in reverse order.  That lets the outer config overwrite locations from
+  // the inner configs.
+  for (auto i = maps->rbegin(); i != maps->rend(); ++i) {
+    if (i->has_match() && i->match()->has_name() && i->has_rename() &&
+        i->rename()->has_name() && i->match()->name()->string_view() == *name) {
+      VLOG(1) << "Renamed \"" << *name << "\" to \""
+              << i->rename()->name()->string_view() << "\"";
+      *name = i->rename()->name()->string_view();
+    }
+  }
+}
+
 }  // namespace
 
 const char *GetRootDirectory() {
@@ -112,5 +381,55 @@
   return *once.Get();
 }
 
+Flatbuffer<Configuration> ReadConfig(const absl::string_view path) {
+  // We only want to read a file once.  So track the visited files in a set.
+  absl::btree_set<std::string> visited_paths;
+  return MergeConfiguration(ReadConfig(path, &visited_paths));
+}
+
+const Location *GetLocation(const Flatbuffer<Configuration> &config,
+                            absl::string_view name, absl::string_view type,
+                            absl::string_view application_name) {
+  VLOG(1) << "Looking up { \"name\": \"" << name << "\", \"type\": \"" << type
+          << "\" }";
+
+  // First handle application specific maps.  Only do this if we have a matching
+  // application name, and it has maps.
+  if (config.message().has_applications()) {
+    auto application_iterator =
+        std::lower_bound(config.message().applications()->cbegin(),
+                         config.message().applications()->cend(),
+                         application_name, CompareApplications);
+    if (application_iterator != config.message().applications()->cend() &&
+        EqualsApplications(*application_iterator, application_name)) {
+      if (application_iterator->has_maps()) {
+        HandleMaps(application_iterator->maps(), &name);
+      }
+    }
+  }
+
+  // Now do global maps.
+  if (config.message().has_maps()) {
+    HandleMaps(config.message().maps(), &name);
+  }
+
+  // Then look for the location.
+  auto location_iterator =
+      std::lower_bound(config.message().locations()->cbegin(),
+                       config.message().locations()->cend(),
+                       std::make_pair(name, type), CompareLocations);
+
+  // Make sure we actually found it, and it matches.
+  if (location_iterator != config.message().locations()->cend() &&
+      EqualsLocations(*location_iterator, std::make_pair(name, type))) {
+    VLOG(1) << "Found: " << FlatbufferToJson(*location_iterator);
+    return *location_iterator;
+  } else {
+    VLOG(1) << "No match for { \"name\": \"" << name << "\", \"type\": \""
+            << type << "\" }";
+    return nullptr;
+  }
+}
+
 }  // namespace configuration
 }  // namespace aos