diff --git a/src/entity_manager.cpp b/src/entity_manager.cpp
new file mode 100644
index 0000000..641d3f9
--- /dev/null
+++ b/src/entity_manager.cpp
@@ -0,0 +1,1166 @@
+/*
+// Copyright (c) 2018 Intel Corporation
+//
+// 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.
+*/
+/// \file entity_manager.cpp
+
+#include "entity_manager.hpp"
+
+#include "overlay.hpp"
+#include "utils.hpp"
+#include "variant_visitors.hpp"
+
+#include <boost/algorithm/string/case_conv.hpp>
+#include <boost/algorithm/string/classification.hpp>
+#include <boost/algorithm/string/predicate.hpp>
+#include <boost/algorithm/string/replace.hpp>
+#include <boost/algorithm/string/split.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/steady_timer.hpp>
+#include <boost/container/flat_map.hpp>
+#include <boost/container/flat_set.hpp>
+#include <boost/range/iterator_range.hpp>
+#include <nlohmann/json.hpp>
+#include <sdbusplus/asio/connection.hpp>
+#include <sdbusplus/asio/object_server.hpp>
+
+#include <charconv>
+#include <filesystem>
+#include <fstream>
+#include <functional>
+#include <iostream>
+#include <map>
+#include <regex>
+#include <variant>
+constexpr const char* hostConfigurationDirectory = SYSCONF_DIR "configurations";
+constexpr const char* configurationDirectory = PACKAGE_DIR "configurations";
+constexpr const char* schemaDirectory = PACKAGE_DIR "configurations/schemas";
+constexpr const char* tempConfigDir = "/tmp/configuration/";
+constexpr const char* lastConfiguration = "/tmp/configuration/last.json";
+constexpr const char* currentConfiguration = "/var/configuration/system.json";
+constexpr const char* globalSchema = "global.json";
+
+const boost::container::flat_map<const char*, probe_type_codes, CmpStr>
+    probeTypes{{{"FALSE", probe_type_codes::FALSE_T},
+                {"TRUE", probe_type_codes::TRUE_T},
+                {"AND", probe_type_codes::AND},
+                {"OR", probe_type_codes::OR},
+                {"FOUND", probe_type_codes::FOUND},
+                {"MATCH_ONE", probe_type_codes::MATCH_ONE}}};
+
+static constexpr std::array<const char*, 6> settableInterfaces = {
+    "FanProfile", "Pid", "Pid.Zone", "Stepwise", "Thresholds", "Polling"};
+using JsonVariantType =
+    std::variant<std::vector<std::string>, std::vector<double>, std::string,
+                 int64_t, uint64_t, double, int32_t, uint32_t, int16_t,
+                 uint16_t, uint8_t, bool>;
+
+// store reference to all interfaces so we can destroy them later
+boost::container::flat_map<
+    std::string, std::vector<std::weak_ptr<sdbusplus::asio::dbus_interface>>>
+    inventory;
+
+// todo: pass this through nicer
+std::shared_ptr<sdbusplus::asio::connection> systemBus;
+nlohmann::json lastJson;
+
+boost::asio::io_context io;
+
+const std::regex illegalDbusPathRegex("[^A-Za-z0-9_.]");
+const std::regex illegalDbusMemberRegex("[^A-Za-z0-9_]");
+
+FoundProbeTypeT findProbeType(const std::string& probe)
+{
+    boost::container::flat_map<const char*, probe_type_codes,
+                               CmpStr>::const_iterator probeType;
+    for (probeType = probeTypes.begin(); probeType != probeTypes.end();
+         ++probeType)
+    {
+        if (probe.find(probeType->first) != std::string::npos)
+        {
+            return probeType;
+        }
+    }
+
+    return std::nullopt;
+}
+
+static std::shared_ptr<sdbusplus::asio::dbus_interface>
+    createInterface(sdbusplus::asio::object_server& objServer,
+                    const std::string& path, const std::string& interface,
+                    const std::string& parent, bool checkNull = false)
+{
+    // on first add we have no reason to check for null before add, as there
+    // won't be any. For dynamically added interfaces, we check for null so that
+    // a constant delete/add will not create a memory leak
+
+    auto ptr = objServer.add_interface(path, interface);
+    auto& dataVector = inventory[parent];
+    if (checkNull)
+    {
+        auto it = std::find_if(dataVector.begin(), dataVector.end(),
+                               [](const auto& p) { return p.expired(); });
+        if (it != dataVector.end())
+        {
+            *it = ptr;
+            return ptr;
+        }
+    }
+    dataVector.emplace_back(ptr);
+    return ptr;
+}
+
+// writes output files to persist data
+bool writeJsonFiles(const nlohmann::json& systemConfiguration)
+{
+    std::filesystem::create_directory(configurationOutDir);
+    std::ofstream output(currentConfiguration);
+    if (!output.good())
+    {
+        return false;
+    }
+    output << systemConfiguration.dump(4);
+    output.close();
+    return true;
+}
+
+template <typename JsonType>
+bool setJsonFromPointer(const std::string& ptrStr, const JsonType& value,
+                        nlohmann::json& systemConfiguration)
+{
+    try
+    {
+        nlohmann::json::json_pointer ptr(ptrStr);
+        nlohmann::json& ref = systemConfiguration[ptr];
+        ref = value;
+        return true;
+    }
+    catch (const std::out_of_range&)
+    {
+        return false;
+    }
+}
+
+// template function to add array as dbus property
+template <typename PropertyType>
+void addArrayToDbus(const std::string& name, const nlohmann::json& array,
+                    sdbusplus::asio::dbus_interface* iface,
+                    sdbusplus::asio::PropertyPermission permission,
+                    nlohmann::json& systemConfiguration,
+                    const std::string& jsonPointerString)
+{
+    std::vector<PropertyType> values;
+    for (const auto& property : array)
+    {
+        auto ptr = property.get_ptr<const PropertyType*>();
+        if (ptr != nullptr)
+        {
+            values.emplace_back(*ptr);
+        }
+    }
+
+    if (permission == sdbusplus::asio::PropertyPermission::readOnly)
+    {
+        iface->register_property(name, values);
+    }
+    else
+    {
+        iface->register_property(
+            name, values,
+            [&systemConfiguration,
+             jsonPointerString{std::string(jsonPointerString)}](
+                const std::vector<PropertyType>& newVal,
+                std::vector<PropertyType>& val) {
+                val = newVal;
+                if (!setJsonFromPointer(jsonPointerString, val,
+                                        systemConfiguration))
+                {
+                    std::cerr << "error setting json field\n";
+                    return -1;
+                }
+                if (!writeJsonFiles(systemConfiguration))
+                {
+                    std::cerr << "error setting json file\n";
+                    return -1;
+                }
+                return 1;
+            });
+    }
+}
+
+template <typename PropertyType>
+void addProperty(const std::string& propertyName, const PropertyType& value,
+                 sdbusplus::asio::dbus_interface* iface,
+                 nlohmann::json& systemConfiguration,
+                 const std::string& jsonPointerString,
+                 sdbusplus::asio::PropertyPermission permission)
+{
+    if (permission == sdbusplus::asio::PropertyPermission::readOnly)
+    {
+        iface->register_property(propertyName, value);
+        return;
+    }
+    iface->register_property(
+        propertyName, value,
+        [&systemConfiguration,
+         jsonPointerString{std::string(jsonPointerString)}](
+            const PropertyType& newVal, PropertyType& val) {
+            val = newVal;
+            if (!setJsonFromPointer(jsonPointerString, val,
+                                    systemConfiguration))
+            {
+                std::cerr << "error setting json field\n";
+                return -1;
+            }
+            if (!writeJsonFiles(systemConfiguration))
+            {
+                std::cerr << "error setting json file\n";
+                return -1;
+            }
+            return 1;
+        });
+}
+
+void createDeleteObjectMethod(
+    const std::string& jsonPointerPath,
+    const std::shared_ptr<sdbusplus::asio::dbus_interface>& iface,
+    sdbusplus::asio::object_server& objServer,
+    nlohmann::json& systemConfiguration)
+{
+    std::weak_ptr<sdbusplus::asio::dbus_interface> interface = iface;
+    iface->register_method(
+        "Delete", [&objServer, &systemConfiguration, interface,
+                   jsonPointerPath{std::string(jsonPointerPath)}]() {
+            std::shared_ptr<sdbusplus::asio::dbus_interface> dbusInterface =
+                interface.lock();
+            if (!dbusInterface)
+            {
+                // this technically can't happen as the pointer is pointing to
+                // us
+                throw DBusInternalError();
+            }
+            nlohmann::json::json_pointer ptr(jsonPointerPath);
+            systemConfiguration[ptr] = nullptr;
+
+            // todo(james): dig through sdbusplus to find out why we can't
+            // delete it in a method call
+            io.post([&objServer, dbusInterface]() mutable {
+                objServer.remove_interface(dbusInterface);
+            });
+
+            if (!writeJsonFiles(systemConfiguration))
+            {
+                std::cerr << "error setting json file\n";
+                throw DBusInternalError();
+            }
+        });
+}
+
+// adds simple json types to interface's properties
+void populateInterfaceFromJson(
+    nlohmann::json& systemConfiguration, const std::string& jsonPointerPath,
+    std::shared_ptr<sdbusplus::asio::dbus_interface>& iface,
+    nlohmann::json& dict, sdbusplus::asio::object_server& objServer,
+    sdbusplus::asio::PropertyPermission permission =
+        sdbusplus::asio::PropertyPermission::readOnly)
+{
+    for (auto& [key, value] : dict.items())
+    {
+        auto type = value.type();
+        bool array = false;
+        if (value.type() == nlohmann::json::value_t::array)
+        {
+            array = true;
+            if (!value.size())
+            {
+                continue;
+            }
+            type = value[0].type();
+            bool isLegal = true;
+            for (const auto& arrayItem : value)
+            {
+                if (arrayItem.type() != type)
+                {
+                    isLegal = false;
+                    break;
+                }
+            }
+            if (!isLegal)
+            {
+                std::cerr << "dbus format error" << value << "\n";
+                continue;
+            }
+        }
+        if (type == nlohmann::json::value_t::object)
+        {
+            continue; // handled elsewhere
+        }
+
+        std::string path = jsonPointerPath;
+        path.append("/").append(key);
+        if (permission == sdbusplus::asio::PropertyPermission::readWrite)
+        {
+            // all setable numbers are doubles as it is difficult to always
+            // create a configuration file with all whole numbers as decimals
+            // i.e. 1.0
+            if (array)
+            {
+                if (value[0].is_number())
+                {
+                    type = nlohmann::json::value_t::number_float;
+                }
+            }
+            else if (value.is_number())
+            {
+                type = nlohmann::json::value_t::number_float;
+            }
+        }
+
+        switch (type)
+        {
+            case (nlohmann::json::value_t::boolean):
+            {
+                if (array)
+                {
+                    // todo: array of bool isn't detected correctly by
+                    // sdbusplus, change it to numbers
+                    addArrayToDbus<uint64_t>(key, value, iface.get(),
+                                             permission, systemConfiguration,
+                                             path);
+                }
+
+                else
+                {
+                    addProperty(key, value.get<bool>(), iface.get(),
+                                systemConfiguration, path, permission);
+                }
+                break;
+            }
+            case (nlohmann::json::value_t::number_integer):
+            {
+                if (array)
+                {
+                    addArrayToDbus<int64_t>(key, value, iface.get(), permission,
+                                            systemConfiguration, path);
+                }
+                else
+                {
+                    addProperty(key, value.get<int64_t>(), iface.get(),
+                                systemConfiguration, path,
+                                sdbusplus::asio::PropertyPermission::readOnly);
+                }
+                break;
+            }
+            case (nlohmann::json::value_t::number_unsigned):
+            {
+                if (array)
+                {
+                    addArrayToDbus<uint64_t>(key, value, iface.get(),
+                                             permission, systemConfiguration,
+                                             path);
+                }
+                else
+                {
+                    addProperty(key, value.get<uint64_t>(), iface.get(),
+                                systemConfiguration, path,
+                                sdbusplus::asio::PropertyPermission::readOnly);
+                }
+                break;
+            }
+            case (nlohmann::json::value_t::number_float):
+            {
+                if (array)
+                {
+                    addArrayToDbus<double>(key, value, iface.get(), permission,
+                                           systemConfiguration, path);
+                }
+
+                else
+                {
+                    addProperty(key, value.get<double>(), iface.get(),
+                                systemConfiguration, path, permission);
+                }
+                break;
+            }
+            case (nlohmann::json::value_t::string):
+            {
+                if (array)
+                {
+                    addArrayToDbus<std::string>(key, value, iface.get(),
+                                                permission, systemConfiguration,
+                                                path);
+                }
+                else
+                {
+                    addProperty(key, value.get<std::string>(), iface.get(),
+                                systemConfiguration, path, permission);
+                }
+                break;
+            }
+            default:
+            {
+                std::cerr << "Unexpected json type in system configuration "
+                          << key << ": " << value.type_name() << "\n";
+                break;
+            }
+        }
+    }
+    if (permission == sdbusplus::asio::PropertyPermission::readWrite)
+    {
+        createDeleteObjectMethod(jsonPointerPath, iface, objServer,
+                                 systemConfiguration);
+    }
+    iface->initialize();
+}
+
+sdbusplus::asio::PropertyPermission getPermission(const std::string& interface)
+{
+    return std::find(settableInterfaces.begin(), settableInterfaces.end(),
+                     interface) != settableInterfaces.end()
+               ? sdbusplus::asio::PropertyPermission::readWrite
+               : sdbusplus::asio::PropertyPermission::readOnly;
+}
+
+void createAddObjectMethod(const std::string& jsonPointerPath,
+                           const std::string& path,
+                           nlohmann::json& systemConfiguration,
+                           sdbusplus::asio::object_server& objServer,
+                           const std::string& board)
+{
+    std::shared_ptr<sdbusplus::asio::dbus_interface> iface = createInterface(
+        objServer, path, "xyz.openbmc_project.AddObject", board);
+
+    iface->register_method(
+        "AddObject",
+        [&systemConfiguration, &objServer,
+         jsonPointerPath{std::string(jsonPointerPath)}, path{std::string(path)},
+         board](const boost::container::flat_map<std::string, JsonVariantType>&
+                    data) {
+            nlohmann::json::json_pointer ptr(jsonPointerPath);
+            nlohmann::json& base = systemConfiguration[ptr];
+            auto findExposes = base.find("Exposes");
+
+            if (findExposes == base.end())
+            {
+                throw std::invalid_argument("Entity must have children.");
+            }
+
+            // this will throw invalid-argument to sdbusplus if invalid json
+            nlohmann::json newData{};
+            for (const auto& item : data)
+            {
+                nlohmann::json& newJson = newData[item.first];
+                std::visit([&newJson](auto&& val) { newJson = std::move(val); },
+                           item.second);
+            }
+
+            auto findName = newData.find("Name");
+            auto findType = newData.find("Type");
+            if (findName == newData.end() || findType == newData.end())
+            {
+                throw std::invalid_argument("AddObject missing Name or Type");
+            }
+            const std::string* type = findType->get_ptr<const std::string*>();
+            const std::string* name = findName->get_ptr<const std::string*>();
+            if (type == nullptr || name == nullptr)
+            {
+                throw std::invalid_argument("Type and Name must be a string.");
+            }
+
+            bool foundNull = false;
+            size_t lastIndex = 0;
+            // we add in the "exposes"
+            for (const auto& expose : *findExposes)
+            {
+                if (expose.is_null())
+                {
+                    foundNull = true;
+                    continue;
+                }
+
+                if (expose["Name"] == *name && expose["Type"] == *type)
+                {
+                    throw std::invalid_argument(
+                        "Field already in JSON, not adding");
+                }
+
+                if (foundNull)
+                {
+                    continue;
+                }
+
+                lastIndex++;
+            }
+
+            std::ifstream schemaFile(std::string(schemaDirectory) + "/" +
+                                     *type + ".json");
+            // todo(james) we might want to also make a list of 'can add'
+            // interfaces but for now I think the assumption if there is a
+            // schema avaliable that it is allowed to update is fine
+            if (!schemaFile.good())
+            {
+                throw std::invalid_argument(
+                    "No schema avaliable, cannot validate.");
+            }
+            nlohmann::json schema =
+                nlohmann::json::parse(schemaFile, nullptr, false);
+            if (schema.is_discarded())
+            {
+                std::cerr << "Schema not legal" << *type << ".json\n";
+                throw DBusInternalError();
+            }
+            if (!validateJson(schema, newData))
+            {
+                throw std::invalid_argument("Data does not match schema");
+            }
+            if (foundNull)
+            {
+                findExposes->at(lastIndex) = newData;
+            }
+            else
+            {
+                findExposes->push_back(newData);
+            }
+            if (!writeJsonFiles(systemConfiguration))
+            {
+                std::cerr << "Error writing json files\n";
+                throw DBusInternalError();
+            }
+            std::string dbusName = *name;
+
+            std::regex_replace(dbusName.begin(), dbusName.begin(),
+                               dbusName.end(), illegalDbusMemberRegex, "_");
+
+            std::shared_ptr<sdbusplus::asio::dbus_interface> interface =
+                createInterface(objServer, path + "/" + dbusName,
+                                "xyz.openbmc_project.Configuration." + *type,
+                                board, true);
+            // permission is read-write, as since we just created it, must be
+            // runtime modifiable
+            populateInterfaceFromJson(
+                systemConfiguration,
+                jsonPointerPath + "/Exposes/" + std::to_string(lastIndex),
+                interface, newData, objServer,
+                sdbusplus::asio::PropertyPermission::readWrite);
+        });
+    iface->initialize();
+}
+
+void postToDbus(const nlohmann::json& newConfiguration,
+                nlohmann::json& systemConfiguration,
+                sdbusplus::asio::object_server& objServer)
+
+{
+    // iterate through boards
+    for (auto& [boardId, boardConfig] : newConfiguration.items())
+    {
+        std::string boardKey = boardConfig["Name"];
+        std::string boardKeyOrig = boardConfig["Name"];
+        std::string jsonPointerPath = "/" + boardId;
+        // loop through newConfiguration, but use values from system
+        // configuration to be able to modify via dbus later
+        auto boardValues = systemConfiguration[boardId];
+        auto findBoardType = boardValues.find("Type");
+        std::string boardType;
+        if (findBoardType != boardValues.end() &&
+            findBoardType->type() == nlohmann::json::value_t::string)
+        {
+            boardType = findBoardType->get<std::string>();
+            std::regex_replace(boardType.begin(), boardType.begin(),
+                               boardType.end(), illegalDbusMemberRegex, "_");
+        }
+        else
+        {
+            std::cerr << "Unable to find type for " << boardKey
+                      << " reverting to Chassis.\n";
+            boardType = "Chassis";
+        }
+        std::string boardtypeLower = boost::algorithm::to_lower_copy(boardType);
+
+        std::regex_replace(boardKey.begin(), boardKey.begin(), boardKey.end(),
+                           illegalDbusMemberRegex, "_");
+        std::string boardName = "/xyz/openbmc_project/inventory/system/";
+        boardName += boardtypeLower;
+        boardName += "/";
+        boardName += boardKey;
+
+        std::shared_ptr<sdbusplus::asio::dbus_interface> inventoryIface =
+            createInterface(objServer, boardName,
+                            "xyz.openbmc_project.Inventory.Item", boardKey);
+
+        std::shared_ptr<sdbusplus::asio::dbus_interface> boardIface =
+            createInterface(objServer, boardName,
+                            "xyz.openbmc_project.Inventory.Item." + boardType,
+                            boardKeyOrig);
+
+        createAddObjectMethod(jsonPointerPath, boardName, systemConfiguration,
+                              objServer, boardKeyOrig);
+
+        populateInterfaceFromJson(systemConfiguration, jsonPointerPath,
+                                  boardIface, boardValues, objServer);
+        jsonPointerPath += "/";
+        // iterate through board properties
+        for (auto& [propName, propValue] : boardValues.items())
+        {
+            if (propValue.type() == nlohmann::json::value_t::object)
+            {
+                std::shared_ptr<sdbusplus::asio::dbus_interface> iface =
+                    createInterface(objServer, boardName, propName,
+                                    boardKeyOrig);
+
+                populateInterfaceFromJson(systemConfiguration,
+                                          jsonPointerPath + propName, iface,
+                                          propValue, objServer);
+            }
+        }
+
+        auto exposes = boardValues.find("Exposes");
+        if (exposes == boardValues.end())
+        {
+            continue;
+        }
+        // iterate through exposes
+        jsonPointerPath += "Exposes/";
+
+        // store the board level pointer so we can modify it on the way down
+        std::string jsonPointerPathBoard = jsonPointerPath;
+        size_t exposesIndex = -1;
+        for (auto& item : *exposes)
+        {
+            exposesIndex++;
+            jsonPointerPath = jsonPointerPathBoard;
+            jsonPointerPath += std::to_string(exposesIndex);
+
+            auto findName = item.find("Name");
+            if (findName == item.end())
+            {
+                std::cerr << "cannot find name in field " << item << "\n";
+                continue;
+            }
+            auto findStatus = item.find("Status");
+            // if status is not found it is assumed to be status = 'okay'
+            if (findStatus != item.end())
+            {
+                if (*findStatus == "disabled")
+                {
+                    continue;
+                }
+            }
+            auto findType = item.find("Type");
+            std::string itemType;
+            if (findType != item.end())
+            {
+                itemType = findType->get<std::string>();
+                std::regex_replace(itemType.begin(), itemType.begin(),
+                                   itemType.end(), illegalDbusPathRegex, "_");
+            }
+            else
+            {
+                itemType = "unknown";
+            }
+            std::string itemName = findName->get<std::string>();
+            std::regex_replace(itemName.begin(), itemName.begin(),
+                               itemName.end(), illegalDbusMemberRegex, "_");
+            std::string ifacePath = boardName;
+            ifacePath += "/";
+            ifacePath += itemName;
+
+            std::shared_ptr<sdbusplus::asio::dbus_interface> itemIface =
+                createInterface(objServer, ifacePath,
+                                "xyz.openbmc_project.Configuration." + itemType,
+                                boardKeyOrig);
+
+            populateInterfaceFromJson(systemConfiguration, jsonPointerPath,
+                                      itemIface, item, objServer,
+                                      getPermission(itemType));
+
+            for (auto& [name, config] : item.items())
+            {
+                jsonPointerPath = jsonPointerPathBoard;
+                jsonPointerPath.append(std::to_string(exposesIndex))
+                    .append("/")
+                    .append(name);
+                if (config.type() == nlohmann::json::value_t::object)
+                {
+                    std::string ifaceName =
+                        "xyz.openbmc_project.Configuration.";
+                    ifaceName.append(itemType).append(".").append(name);
+
+                    std::shared_ptr<sdbusplus::asio::dbus_interface>
+                        objectIface = createInterface(objServer, ifacePath,
+                                                      ifaceName, boardKeyOrig);
+
+                    populateInterfaceFromJson(
+                        systemConfiguration, jsonPointerPath, objectIface,
+                        config, objServer, getPermission(name));
+                }
+                else if (config.type() == nlohmann::json::value_t::array)
+                {
+                    size_t index = 0;
+                    if (!config.size())
+                    {
+                        continue;
+                    }
+                    bool isLegal = true;
+                    auto type = config[0].type();
+                    if (type != nlohmann::json::value_t::object)
+                    {
+                        continue;
+                    }
+
+                    // verify legal json
+                    for (const auto& arrayItem : config)
+                    {
+                        if (arrayItem.type() != type)
+                        {
+                            isLegal = false;
+                            break;
+                        }
+                    }
+                    if (!isLegal)
+                    {
+                        std::cerr << "dbus format error" << config << "\n";
+                        break;
+                    }
+
+                    for (auto& arrayItem : config)
+                    {
+                        std::string ifaceName =
+                            "xyz.openbmc_project.Configuration.";
+                        ifaceName.append(itemType).append(".").append(name);
+                        ifaceName.append(std::to_string(index));
+
+                        std::shared_ptr<sdbusplus::asio::dbus_interface>
+                            objectIface = createInterface(
+                                objServer, ifacePath, ifaceName, boardKeyOrig);
+
+                        populateInterfaceFromJson(
+                            systemConfiguration,
+                            jsonPointerPath + "/" + std::to_string(index),
+                            objectIface, arrayItem, objServer,
+                            getPermission(name));
+                        index++;
+                    }
+                }
+            }
+        }
+    }
+}
+
+// reads json files out of the filesystem
+bool loadConfigurations(std::list<nlohmann::json>& configurations)
+{
+    // find configuration files
+    std::vector<std::filesystem::path> jsonPaths;
+    if (!findFiles(
+            std::vector<std::filesystem::path>{configurationDirectory,
+                                               hostConfigurationDirectory},
+            R"(.*\.json)", jsonPaths))
+    {
+        std::cerr << "Unable to find any configuration files in "
+                  << configurationDirectory << "\n";
+        return false;
+    }
+
+    std::ifstream schemaStream(std::string(schemaDirectory) + "/" +
+                               globalSchema);
+    if (!schemaStream.good())
+    {
+        std::cerr
+            << "Cannot open schema file,  cannot validate JSON, exiting\n\n";
+        std::exit(EXIT_FAILURE);
+        return false;
+    }
+    nlohmann::json schema = nlohmann::json::parse(schemaStream, nullptr, false);
+    if (schema.is_discarded())
+    {
+        std::cerr
+            << "Illegal schema file detected, cannot validate JSON, exiting\n";
+        std::exit(EXIT_FAILURE);
+        return false;
+    }
+
+    for (auto& jsonPath : jsonPaths)
+    {
+        std::ifstream jsonStream(jsonPath.c_str());
+        if (!jsonStream.good())
+        {
+            std::cerr << "unable to open " << jsonPath.string() << "\n";
+            continue;
+        }
+        auto data = nlohmann::json::parse(jsonStream, nullptr, false);
+        if (data.is_discarded())
+        {
+            std::cerr << "syntax error in " << jsonPath.string() << "\n";
+            continue;
+        }
+        /*
+         * todo(james): reenable this once less things are in flight
+         *
+        if (!validateJson(schema, data))
+        {
+            std::cerr << "Error validating " << jsonPath.string() << "\n";
+            continue;
+        }
+        */
+
+        if (data.type() == nlohmann::json::value_t::array)
+        {
+            for (auto& d : data)
+            {
+                configurations.emplace_back(d);
+            }
+        }
+        else
+        {
+            configurations.emplace_back(data);
+        }
+    }
+    return true;
+}
+
+static bool deviceRequiresPowerOn(const nlohmann::json& entity)
+{
+    auto powerState = entity.find("PowerState");
+    if (powerState == entity.end())
+    {
+        return false;
+    }
+
+    auto ptr = powerState->get_ptr<const std::string*>();
+    if (!ptr)
+    {
+        return false;
+    }
+
+    return *ptr == "On" || *ptr == "BiosPost";
+}
+
+static void pruneDevice(const nlohmann::json& systemConfiguration,
+                        const bool powerOff, const bool scannedPowerOff,
+                        const std::string& name, const nlohmann::json& device)
+{
+    if (systemConfiguration.contains(name))
+    {
+        return;
+    }
+
+    if (deviceRequiresPowerOn(device) && (powerOff || scannedPowerOff))
+    {
+        return;
+    }
+
+    logDeviceRemoved(device);
+}
+
+void startRemovedTimer(boost::asio::steady_timer& timer,
+                       nlohmann::json& systemConfiguration)
+{
+    static bool scannedPowerOff = false;
+    static bool scannedPowerOn = false;
+
+    if (systemConfiguration.empty() || lastJson.empty())
+    {
+        return; // not ready yet
+    }
+    if (scannedPowerOn)
+    {
+        return;
+    }
+
+    if (!isPowerOn() && scannedPowerOff)
+    {
+        return;
+    }
+
+    timer.expires_after(std::chrono::seconds(10));
+    timer.async_wait(
+        [&systemConfiguration](const boost::system::error_code& ec) {
+            if (ec == boost::asio::error::operation_aborted)
+            {
+                return;
+            }
+
+            bool powerOff = !isPowerOn();
+            for (const auto& [name, device] : lastJson.items())
+            {
+                pruneDevice(systemConfiguration, powerOff, scannedPowerOff,
+                            name, device);
+            }
+
+            scannedPowerOff = true;
+            if (!powerOff)
+            {
+                scannedPowerOn = true;
+            }
+        });
+}
+
+static std::vector<std::weak_ptr<sdbusplus::asio::dbus_interface>>&
+    getDeviceInterfaces(const nlohmann::json& device)
+{
+    return inventory[device["Name"].get<std::string>()];
+}
+
+static void pruneConfiguration(nlohmann::json& systemConfiguration,
+                               sdbusplus::asio::object_server& objServer,
+                               bool powerOff, const std::string& name,
+                               const nlohmann::json& device)
+{
+    if (powerOff && deviceRequiresPowerOn(device))
+    {
+        // power not on yet, don't know if it's there or not
+        return;
+    }
+
+    auto& ifaces = getDeviceInterfaces(device);
+    for (auto& iface : ifaces)
+    {
+        auto sharedPtr = iface.lock();
+        if (!!sharedPtr)
+        {
+            objServer.remove_interface(sharedPtr);
+        }
+    }
+
+    ifaces.clear();
+    systemConfiguration.erase(name);
+    logDeviceRemoved(device);
+}
+
+static void deriveNewConfiguration(const nlohmann::json& oldConfiguration,
+                                   nlohmann::json& newConfiguration)
+{
+    for (auto it = newConfiguration.begin(); it != newConfiguration.end();)
+    {
+        auto findKey = oldConfiguration.find(it.key());
+        if (findKey != oldConfiguration.end())
+        {
+            it = newConfiguration.erase(it);
+        }
+        else
+        {
+            it++;
+        }
+    }
+}
+
+static void publishNewConfiguration(
+    const size_t& instance, const size_t count,
+    boost::asio::steady_timer& timer, nlohmann::json& systemConfiguration,
+    // Gerrit discussion:
+    // https://gerrit.openbmc-project.xyz/c/openbmc/entity-manager/+/52316/6
+    //
+    // Discord discussion:
+    // https://discord.com/channels/775381525260664832/867820390406422538/958048437729910854
+    //
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
+    const nlohmann::json newConfiguration,
+    sdbusplus::asio::object_server& objServer)
+{
+    loadOverlays(newConfiguration);
+
+    io.post([systemConfiguration]() {
+        if (!writeJsonFiles(systemConfiguration))
+        {
+            std::cerr << "Error writing json files\n";
+        }
+    });
+
+    io.post([&instance, count, &timer, newConfiguration, &systemConfiguration,
+             &objServer]() {
+        postToDbus(newConfiguration, systemConfiguration, objServer);
+        if (count == instance)
+        {
+            startRemovedTimer(timer, systemConfiguration);
+        }
+    });
+}
+
+// main properties changed entry
+void propertiesChangedCallback(nlohmann::json& systemConfiguration,
+                               sdbusplus::asio::object_server& objServer)
+{
+    static bool inProgress = false;
+    static boost::asio::steady_timer timer(io);
+    static size_t instance = 0;
+    instance++;
+    size_t count = instance;
+
+    timer.expires_after(std::chrono::seconds(5));
+
+    // setup an async wait as we normally get flooded with new requests
+    timer.async_wait([&systemConfiguration, &objServer,
+                      count](const boost::system::error_code& ec) {
+        if (ec == boost::asio::error::operation_aborted)
+        {
+            // we were cancelled
+            return;
+        }
+        if (ec)
+        {
+            std::cerr << "async wait error " << ec << "\n";
+            return;
+        }
+
+        if (inProgress)
+        {
+            propertiesChangedCallback(systemConfiguration, objServer);
+            return;
+        }
+        inProgress = true;
+
+        nlohmann::json oldConfiguration = systemConfiguration;
+        auto missingConfigurations = std::make_shared<nlohmann::json>();
+        *missingConfigurations = systemConfiguration;
+
+        std::list<nlohmann::json> configurations;
+        if (!loadConfigurations(configurations))
+        {
+            std::cerr << "Could not load configurations\n";
+            inProgress = false;
+            return;
+        }
+
+        auto perfScan = std::make_shared<PerformScan>(
+            systemConfiguration, *missingConfigurations, configurations,
+            objServer,
+            [&systemConfiguration, &objServer, count, oldConfiguration,
+             missingConfigurations]() {
+                // this is something that since ac has been applied to the bmc
+                // we saw, and we no longer see it
+                bool powerOff = !isPowerOn();
+                for (const auto& [name, device] :
+                     missingConfigurations->items())
+                {
+                    pruneConfiguration(systemConfiguration, objServer, powerOff,
+                                       name, device);
+                }
+
+                nlohmann::json newConfiguration = systemConfiguration;
+
+                deriveNewConfiguration(oldConfiguration, newConfiguration);
+
+                for (const auto& [_, device] : newConfiguration.items())
+                {
+                    logDeviceAdded(device);
+                }
+
+                inProgress = false;
+
+                io.post(std::bind_front(
+                    publishNewConfiguration, std::ref(instance), count,
+                    std::ref(timer), std::ref(systemConfiguration),
+                    newConfiguration, std::ref(objServer)));
+            });
+        perfScan->run();
+    });
+}
+
+int main()
+{
+    // setup connection to dbus
+    systemBus = std::make_shared<sdbusplus::asio::connection>(io);
+    systemBus->request_name("xyz.openbmc_project.EntityManager");
+
+    sdbusplus::asio::object_server objServer(systemBus);
+
+    std::shared_ptr<sdbusplus::asio::dbus_interface> entityIface =
+        objServer.add_interface("/xyz/openbmc_project/EntityManager",
+                                "xyz.openbmc_project.EntityManager");
+
+    // to keep reference to the match / filter objects so they don't get
+    // destroyed
+
+    nlohmann::json systemConfiguration = nlohmann::json::object();
+
+    // We need a poke from DBus for static providers that create all their
+    // objects prior to claiming a well-known name, and thus don't emit any
+    // org.freedesktop.DBus.Properties signals.  Similarly if a process exits
+    // for any reason, expected or otherwise, we'll need a poke to remove
+    // entities from DBus.
+    sdbusplus::bus::match::match nameOwnerChangedMatch(
+        static_cast<sdbusplus::bus::bus&>(*systemBus),
+        sdbusplus::bus::match::rules::nameOwnerChanged(),
+        [&](sdbusplus::message::message&) {
+            propertiesChangedCallback(systemConfiguration, objServer);
+        });
+    // We also need a poke from DBus when new interfaces are created or
+    // destroyed.
+    sdbusplus::bus::match::match interfacesAddedMatch(
+        static_cast<sdbusplus::bus::bus&>(*systemBus),
+        sdbusplus::bus::match::rules::interfacesAdded(),
+        [&](sdbusplus::message::message&) {
+            propertiesChangedCallback(systemConfiguration, objServer);
+        });
+    sdbusplus::bus::match::match interfacesRemovedMatch(
+        static_cast<sdbusplus::bus::bus&>(*systemBus),
+        sdbusplus::bus::match::rules::interfacesRemoved(),
+        [&](sdbusplus::message::message&) {
+            propertiesChangedCallback(systemConfiguration, objServer);
+        });
+
+    io.post(
+        [&]() { propertiesChangedCallback(systemConfiguration, objServer); });
+
+    entityIface->register_method("ReScan", [&]() {
+        propertiesChangedCallback(systemConfiguration, objServer);
+    });
+    entityIface->initialize();
+
+    if (fwVersionIsSame())
+    {
+        if (std::filesystem::is_regular_file(currentConfiguration))
+        {
+            // this file could just be deleted, but it's nice for debug
+            std::filesystem::create_directory(tempConfigDir);
+            std::filesystem::remove(lastConfiguration);
+            std::filesystem::copy(currentConfiguration, lastConfiguration);
+            std::filesystem::remove(currentConfiguration);
+
+            std::ifstream jsonStream(lastConfiguration);
+            if (jsonStream.good())
+            {
+                auto data = nlohmann::json::parse(jsonStream, nullptr, false);
+                if (data.is_discarded())
+                {
+                    std::cerr << "syntax error in " << lastConfiguration
+                              << "\n";
+                }
+                else
+                {
+                    lastJson = std::move(data);
+                }
+            }
+            else
+            {
+                std::cerr << "unable to open " << lastConfiguration << "\n";
+            }
+        }
+    }
+    else
+    {
+        // not an error, just logging at this level to make it in the journal
+        std::cerr << "Clearing previous configuration\n";
+        std::filesystem::remove(currentConfiguration);
+    }
+
+    // some boards only show up after power is on, we want to not say they are
+    // removed until the same state happens
+    setupPowerMatch(systemBus);
+
+    io.run();
+
+    return 0;
+}