diff --git a/Makefile.am b/Makefile.am
index a341233..c78a537 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -43,6 +43,7 @@
 	firmware_handler.cpp \
 	file_handler.cpp \
 	internal/sys.cpp \
+	prepare_systemd.cpp \
 	verify_systemd.cpp \
 	update_systemd.cpp
 
diff --git a/README.md b/README.md
index 1fc6027..c4e199b 100644
--- a/README.md
+++ b/README.md
@@ -108,6 +108,7 @@
 `STATIC_HANDLER_STAGED_NAME` | `/run/initramfs/bmc-image` | The filename where to write the staged firmware image for static updates.
 `TARBALL_STAGED_NAME`        | `/tmp/image-update.tar`    | The filename where to write the UBI update tarball.
 `HASH_FILENAME`              | `/tmp/bmc.sig`             | The file to use for the hash provided.
+`PREPARATION_DBUS_SERVICE`   | `prepare_update.service`   | The systemd service started when the host starts to send an update.
 `VERIFY_STATUS_FILENAME`     | `/tmp/bmc.verify`          | The file checked for the verification status.
 `VERIFY_DBUS_SERVICE`        | `verify_image.service`     | The systemd service started for verification.
 `UPDATE_DBUS_SERVICE`        | `update-bmc.service`       | The systemd service started for updating the BMC.
diff --git a/configure.ac b/configure.ac
index 8db7aa6..63c0bad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -189,6 +189,10 @@
 AS_IF([test "x$HASH_FILENAME" == "x"], [HASH_FILENAME="/tmp/bmc.sig"])
 AC_DEFINE_UNQUOTED([HASH_FILENAME], ["$HASH_FILENAME"], [The file to use for the hash provided.])
 
+AC_ARG_VAR(PREPARATION_DBUS_SERVICE, [The systemd service started when the host starts to send an update.])
+AS_IF([test "x$PREPARATION_DBUS_SERVICE" == "x"], [PREPARATION_DBUS_SERVICE="prepare_update.service"])
+AC_DEFINE_UNQUOTED([PREPARATION_DBUS_SERVICE], ["$PREPARATION_DBUS_SERVICE"], [The systemd service started when the host starts to send an update.])
+
 AC_ARG_VAR(VERIFY_STATUS_FILENAME, [The file checked for the verification status.])
 AS_IF([test "x$VERIFY_STATUS_FILENAME" == "x"], [VERIFY_STATUS_FILENAME="/tmp/bmc.verify"])
 AC_DEFINE_UNQUOTED([VERIFY_STATUS_FILENAME], ["$VERIFY_STATUS_FILENAME"], [The file checked for the verification status.])
diff --git a/firmware_handler.cpp b/firmware_handler.cpp
index 4967536..aaabe83 100644
--- a/firmware_handler.cpp
+++ b/firmware_handler.cpp
@@ -39,6 +39,7 @@
     FirmwareBlobHandler::CreateFirmwareBlobHandler(
         const std::vector<HandlerPack>& firmwares,
         const std::vector<DataHandlerPack>& transports,
+        std::unique_ptr<TriggerableActionInterface> preparation,
         std::unique_ptr<TriggerableActionInterface> verification,
         std::unique_ptr<TriggerableActionInterface> update)
 {
@@ -72,8 +73,8 @@
     }
 
     return std::make_unique<FirmwareBlobHandler>(
-        firmwares, blobs, transports, bitmask, std::move(verification),
-        std::move(update));
+        firmwares, blobs, transports, bitmask, std::move(preparation),
+        std::move(verification), std::move(update));
 }
 
 /* Check if the path is in our supported list (or active list). */
@@ -712,6 +713,21 @@
 void FirmwareBlobHandler::changeState(UpdateState next)
 {
     state = next;
+
+    if (state == UpdateState::notYetStarted)
+    {
+        /* Going back to notyetstarted, let them trigger preparation again. */
+        preparationTriggered = false;
+    }
+    else if (state == UpdateState::uploadInProgress)
+    {
+        /* Store this transition logic here instead of ::open() */
+        if (!preparationTriggered)
+        {
+            preparation->trigger();
+            preparationTriggered = true;
+        }
+    }
 }
 
 bool FirmwareBlobHandler::expire(uint16_t session)
diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index de37e20..8c7cb04 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -104,6 +104,7 @@
         CreateFirmwareBlobHandler(
             const std::vector<HandlerPack>& firmwares,
             const std::vector<DataHandlerPack>& transports,
+            std::unique_ptr<TriggerableActionInterface> preparation,
             std::unique_ptr<TriggerableActionInterface> verification,
             std::unique_ptr<TriggerableActionInterface> update);
 
@@ -121,13 +122,14 @@
         const std::vector<HandlerPack>& firmwares,
         const std::vector<std::string>& blobs,
         const std::vector<DataHandlerPack>& transports, std::uint16_t bitmask,
+        std::unique_ptr<TriggerableActionInterface> preparation,
         std::unique_ptr<TriggerableActionInterface> verification,
         std::unique_ptr<TriggerableActionInterface> update) :
         handlers(firmwares),
         blobIDs(blobs), transports(transports), bitmask(bitmask),
         activeImage(activeImageBlobId), activeHash(activeHashBlobId),
         verifyImage(verifyBlobId), updateImage(updateBlobId), lookup(),
-        state(UpdateState::notYetStarted),
+        state(UpdateState::notYetStarted), preparation(std::move(preparation)),
         verification(std::move(verification)), update(std::move(update))
     {
     }
@@ -221,6 +223,12 @@
     /** The firmware update state. */
     UpdateState state;
 
+    /* preparation is triggered once we go into uploadInProgress(), but only
+     * once per full cycle, going back to notYetStarted resets this.
+     */
+    bool preparationTriggered = false;
+    std::unique_ptr<TriggerableActionInterface> preparation;
+
     std::unique_ptr<TriggerableActionInterface> verification;
 
     std::unique_ptr<TriggerableActionInterface> update;
diff --git a/main.cpp b/main.cpp
index c857a6a..d28ecba 100644
--- a/main.cpp
+++ b/main.cpp
@@ -23,6 +23,7 @@
 #include "lpc_handler.hpp"
 #include "lpc_nuvoton.hpp"
 #include "pci_handler.hpp"
+#include "prepare_systemd.hpp"
 #include "status.hpp"
 #include "update_systemd.hpp"
 #include "util.hpp"
@@ -113,6 +114,8 @@
 
     auto handler = ipmi_flash::FirmwareBlobHandler::CreateFirmwareBlobHandler(
         ipmi_flash::supportedFirmware, ipmi_flash::supportedTransports,
+        ipmi_flash::SystemdPreparation::CreatePreparation(
+            sdbusplus::bus::new_default(), PREPARATION_DBUS_SERVICE),
         ipmi_flash::SystemdVerification::CreateVerification(
             sdbusplus::bus::new_default(), VERIFY_STATUS_FILENAME,
             VERIFY_DBUS_SERVICE),
diff --git a/prepare_systemd.cpp b/prepare_systemd.cpp
new file mode 100644
index 0000000..b16bc99
--- /dev/null
+++ b/prepare_systemd.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * 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.
+ */
+
+#include "prepare_systemd.hpp"
+
+#include "status.hpp"
+
+#include <memory>
+
+namespace ipmi_flash
+{
+
+std::unique_ptr<TriggerableActionInterface>
+    SystemdPreparation::CreatePreparation(sdbusplus::bus::bus&& bus,
+                                          const std::string& service)
+{
+    return std::make_unique<SystemdPreparation>(std::move(bus), service);
+}
+
+bool SystemdPreparation::trigger()
+{
+    static constexpr auto systemdService = "org.freedesktop.systemd1";
+    static constexpr auto systemdRoot = "/org/freedesktop/systemd1";
+    static constexpr auto systemdInterface = "org.freedesktop.systemd1.Manager";
+
+    auto method = bus.new_method_call(systemdService, systemdRoot,
+                                      systemdInterface, "StartUnit");
+    method.append(triggerService);
+    method.append("replace");
+
+    try
+    {
+        bus.call_noreply(method);
+    }
+    catch (const sdbusplus::exception::SdBusError& ex)
+    {
+        /* TODO: Once logging supports unit-tests, add a log message to test
+         * this failure.
+         */
+        state = ActionStatus::failed;
+        return false;
+    }
+
+    state = ActionStatus::success;
+    return true;
+}
+
+void SystemdPreparation::abort()
+{
+    return;
+}
+
+ActionStatus SystemdPreparation::status()
+{
+    return state;
+}
+
+} // namespace ipmi_flash
diff --git a/prepare_systemd.hpp b/prepare_systemd.hpp
new file mode 100644
index 0000000..af8e065
--- /dev/null
+++ b/prepare_systemd.hpp
@@ -0,0 +1,40 @@
+#pragma once
+
+#include "status.hpp"
+
+#include <memory>
+#include <sdbusplus/bus.hpp>
+#include <string>
+
+namespace ipmi_flash
+{
+
+class SystemdPreparation : public TriggerableActionInterface
+{
+  public:
+    static std::unique_ptr<TriggerableActionInterface>
+        CreatePreparation(sdbusplus::bus::bus&& bus,
+                          const std::string& service);
+
+    SystemdPreparation(sdbusplus::bus::bus&& bus, const std::string& service) :
+        bus(std::move(bus)), triggerService(service)
+    {
+    }
+
+    ~SystemdPreparation() = default;
+    SystemdPreparation(const SystemdPreparation&) = delete;
+    SystemdPreparation& operator=(const SystemdPreparation&) = delete;
+    SystemdPreparation(SystemdPreparation&&) = default;
+    SystemdPreparation& operator=(SystemdPreparation&&) = default;
+
+    bool trigger() override;
+    void abort() override;
+    ActionStatus status() override;
+
+  private:
+    sdbusplus::bus::bus bus;
+    const std::string triggerService;
+    ActionStatus state = ActionStatus::unknown;
+};
+
+} // namespace ipmi_flash
diff --git a/test/firmware_canhandle_unittest.cpp b/test/firmware_canhandle_unittest.cpp
index 7fb4c7f..dabf8ef 100644
--- a/test/firmware_canhandle_unittest.cpp
+++ b/test/firmware_canhandle_unittest.cpp
@@ -33,7 +33,8 @@
     };
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, CreateTriggerMock(), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
 
     for (const auto& item : items)
     {
diff --git a/test/firmware_commit_unittest.cpp b/test/firmware_commit_unittest.cpp
index 11ce3fc..b8c651e 100644
--- a/test/firmware_commit_unittest.cpp
+++ b/test/firmware_commit_unittest.cpp
@@ -49,7 +49,8 @@
         std::make_unique<StrictMock<TriggerMock>>();
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, std::move(verifyMock), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), std::move(verifyMock),
+        CreateTriggerMock());
 
     EXPECT_CALL(imageMock2, open("asdf")).WillOnce(Return(true));
 
@@ -71,7 +72,8 @@
         std::make_unique<StrictMock<TriggerMock>>();
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, std::move(verifyMock), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), std::move(verifyMock),
+        CreateTriggerMock());
 
     EXPECT_CALL(imageMock1, open(StrEq(hashBlobId))).WillOnce(Return(true));
 
diff --git a/test/firmware_createhandler_unittest.cpp b/test/firmware_createhandler_unittest.cpp
index dc6d968..dd09cbe 100644
--- a/test/firmware_createhandler_unittest.cpp
+++ b/test/firmware_createhandler_unittest.cpp
@@ -31,7 +31,8 @@
     };
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, CreateTriggerMock(), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
 
     //    EXPECT_EQ(handler, nullptr);
     EXPECT_FALSE(handler == nullptr);
diff --git a/test/firmware_handler_unittest.cpp b/test/firmware_handler_unittest.cpp
index a5d60f5..27bd517 100644
--- a/test/firmware_handler_unittest.cpp
+++ b/test/firmware_handler_unittest.cpp
@@ -22,7 +22,8 @@
     };
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        {}, data, CreateTriggerMock(), CreateTriggerMock());
+        {}, data, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
     EXPECT_EQ(handler, nullptr);
 }
 TEST(FirmwareHandlerTest, CreateEmptyDataHandlerListFails)
@@ -35,7 +36,8 @@
     };
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, {}, CreateTriggerMock(), CreateTriggerMock());
+        blobs, {}, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
     EXPECT_EQ(handler, nullptr);
 }
 TEST(FirmwareHandlerTest, VerifyHashRequiredForHappiness)
@@ -51,13 +53,15 @@
     };
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, CreateTriggerMock(), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
     EXPECT_EQ(handler, nullptr);
 
     blobs.push_back({hashBlobId, &imageMock});
 
     handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, CreateTriggerMock(), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
     auto result = handler->getBlobIds();
     std::vector<std::string> expectedBlobs = {"asdf", hashBlobId};
     EXPECT_THAT(result, UnorderedElementsAreArray(expectedBlobs));
diff --git a/test/firmware_stat_unittest.cpp b/test/firmware_stat_unittest.cpp
index 4efae94..99ae770 100644
--- a/test/firmware_stat_unittest.cpp
+++ b/test/firmware_stat_unittest.cpp
@@ -29,7 +29,8 @@
     };
 
     auto handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-        blobs, data, CreateTriggerMock(), CreateTriggerMock());
+        blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+        CreateTriggerMock());
 
     blobs::BlobMeta meta;
     EXPECT_TRUE(handler->stat("asdf", &meta));
diff --git a/test/firmware_state_notyetstarted_tarball_unittest.cpp b/test/firmware_state_notyetstarted_tarball_unittest.cpp
index 5aa2baa..275763c 100644
--- a/test/firmware_state_notyetstarted_tarball_unittest.cpp
+++ b/test/firmware_state_notyetstarted_tarball_unittest.cpp
@@ -36,7 +36,8 @@
         updateMockPtr = reinterpret_cast<TriggerMock*>(updateMock.get());
 
         handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-            blobs, data, std::move(verifyMock), std::move(updateMock));
+            blobs, data, CreateTriggerMock(), std::move(verifyMock),
+            std::move(updateMock));
     }
 
     void expectedState(FirmwareBlobHandler::UpdateState state)
diff --git a/test/firmware_state_notyetstarted_unittest.cpp b/test/firmware_state_notyetstarted_unittest.cpp
index 528e47f..54ab7f8 100644
--- a/test/firmware_state_notyetstarted_unittest.cpp
+++ b/test/firmware_state_notyetstarted_unittest.cpp
@@ -93,6 +93,7 @@
 TEST_F(FirmwareHandlerNotYetStartedTest, OpenStaticImageFileVerifyStateChange)
 {
     EXPECT_CALL(imageMock, open(staticLayoutBlobId)).WillOnce(Return(true));
+    EXPECT_CALL(*prepareMockPtr, trigger()).WillOnce(Return(true));
 
     EXPECT_TRUE(handler->open(session, flags, staticLayoutBlobId));
 
@@ -104,6 +105,7 @@
 TEST_F(FirmwareHandlerNotYetStartedTest, OpenHashFileVerifyStateChange)
 {
     EXPECT_CALL(imageMock, open(hashBlobId)).WillOnce(Return(true));
+    EXPECT_CALL(*prepareMockPtr, trigger()).WillOnce(Return(true));
 
     EXPECT_TRUE(handler->open(session, flags, hashBlobId));
 
diff --git a/test/firmware_state_verificationpending_unittest.cpp b/test/firmware_state_verificationpending_unittest.cpp
index 92ba15b..dd2df27 100644
--- a/test/firmware_state_verificationpending_unittest.cpp
+++ b/test/firmware_state_verificationpending_unittest.cpp
@@ -214,6 +214,9 @@
     EXPECT_THAT(handler->getBlobIds(),
                 UnorderedElementsAreArray(expectedBlobs));
 
+    /* Verifies it isn't triggered again. */
+    EXPECT_CALL(*prepareMockPtr, trigger()).Times(0);
+
     EXPECT_CALL(imageMock, open(staticLayoutBlobId)).WillOnce(Return(true));
     EXPECT_TRUE(handler->open(session, flags, staticLayoutBlobId));
     expectedState(FirmwareBlobHandler::UpdateState::uploadInProgress);
diff --git a/test/firmware_unittest.hpp b/test/firmware_unittest.hpp
index e36081d..8d92fe8 100644
--- a/test/firmware_unittest.hpp
+++ b/test/firmware_unittest.hpp
@@ -29,6 +29,10 @@
             {staticLayoutBlobId, &imageMock},
         };
 
+        std::unique_ptr<TriggerableActionInterface> prepareMock =
+            std::make_unique<TriggerMock>();
+        prepareMockPtr = reinterpret_cast<TriggerMock*>(prepareMock.get());
+
         std::unique_ptr<TriggerableActionInterface> verifyMock =
             std::make_unique<TriggerMock>();
         verifyMockPtr = reinterpret_cast<TriggerMock*>(verifyMock.get());
@@ -38,7 +42,8 @@
         updateMockPtr = reinterpret_cast<TriggerMock*>(updateMock.get());
 
         handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-            blobs, data, std::move(verifyMock), std::move(updateMock));
+            blobs, data, std::move(prepareMock), std::move(verifyMock),
+            std::move(updateMock));
     }
 
     void expectedState(FirmwareBlobHandler::UpdateState state)
@@ -50,6 +55,7 @@
     void openToInProgress(const std::string& blobId)
     {
         EXPECT_CALL(imageMock, open(blobId)).WillOnce(Return(true));
+        EXPECT_CALL(*prepareMockPtr, trigger()).WillOnce(Return(true));
         EXPECT_TRUE(handler->open(session, flags, blobId));
         expectedState(FirmwareBlobHandler::UpdateState::uploadInProgress);
     }
@@ -117,6 +123,7 @@
     std::vector<DataHandlerPack> data = {
         {FirmwareBlobHandler::UpdateFlags::ipmi, nullptr}};
     std::unique_ptr<blobs::GenericBlobInterface> handler;
+    TriggerMock* prepareMockPtr;
     TriggerMock* verifyMockPtr;
     TriggerMock* updateMockPtr;
 
@@ -143,7 +150,8 @@
             {"asdf", &imageMock},
         };
         handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-            blobs, data, CreateTriggerMock(), CreateTriggerMock());
+            blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+            CreateTriggerMock());
     }
 };
 
@@ -167,7 +175,8 @@
             {FirmwareBlobHandler::UpdateFlags::lpc, &dataMock},
         };
         handler = FirmwareBlobHandler::CreateFirmwareBlobHandler(
-            blobs, data, CreateTriggerMock(), CreateTriggerMock());
+            blobs, data, CreateTriggerMock(), CreateTriggerMock(),
+            CreateTriggerMock());
     }
 };