diff --git a/model/StubVolume.cpp b/model/StubVolume.cpp
new file mode 100644
index 0000000..edd0861
--- /dev/null
+++ b/model/StubVolume.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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 "StubVolume.h"
+
+#include <android-base/logging.h>
+#include <android-base/stringprintf.h>
+
+using android::base::StringPrintf;
+
+namespace android {
+namespace vold {
+
+StubVolume::StubVolume(int id, const std::string& sourcePath, const std::string& mountPath,
+                       const std::string& fsType, const std::string& fsUuid,
+                       const std::string& fsLabel)
+    : VolumeBase(Type::kStub),
+      mSourcePath(sourcePath),
+      mMountPath(mountPath),
+      mFsType(fsType),
+      mFsUuid(fsUuid),
+      mFsLabel(fsLabel) {
+    setId(StringPrintf("stub:%d", id));
+}
+
+StubVolume::~StubVolume() {}
+
+status_t StubVolume::doCreate() {
+    return OK;
+}
+
+status_t StubVolume::doDestroy() {
+    return OK;
+}
+
+status_t StubVolume::doMount() {
+    auto listener = getListener();
+    if (listener) listener->onVolumeMetadataChanged(getId(), mFsType, mFsUuid, mFsLabel);
+    setInternalPath(mSourcePath);
+    setPath(mMountPath);
+    return OK;
+}
+
+status_t StubVolume::doUnmount() {
+    return OK;
+}
+
+// TODO: return error instead.
+status_t StubVolume::doFormat(const std::string& fsType) {
+    return OK;
+}
+
+}  // namespace vold
+}  // namespace android
diff --git a/model/StubVolume.h b/model/StubVolume.h
new file mode 100644
index 0000000..538cae9
--- /dev/null
+++ b/model/StubVolume.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef ANDROID_VOLD_STUB_VOLUME_H
+#define ANDROID_VOLD_STUB_VOLUME_H
+
+#include "VolumeBase.h"
+
+namespace android {
+namespace vold {
+
+/*
+ * A vold representation of volumes managed from outside Android (e.g., ARC++).
+ *
+ * Used for the case when events such that mounting and unmounting are
+ * actually handled from outside vold, and vold only need to keep track on those
+ * vents instead of talking to kernel directly.
+ */
+class StubVolume : public VolumeBase {
+  public:
+    StubVolume(int id, const std::string& sourcePath, const std::string& mountPath,
+               const std::string& fsType, const std::string& fsUuid, const std::string& fsLabel);
+    virtual ~StubVolume();
+
+  protected:
+    status_t doCreate() override;
+    status_t doDestroy() override;
+    status_t doMount() override;
+    status_t doUnmount() override;
+    status_t doFormat(const std::string& fsType) override;
+
+  private:
+    const std::string mSourcePath;
+    const std::string mMountPath;
+    const std::string mFsType;
+    const std::string mFsUuid;
+    const std::string mFsLabel;
+
+    DISALLOW_COPY_AND_ASSIGN(StubVolume);
+};
+
+}  // namespace vold
+}  // namespace android
+
+#endif
diff --git a/model/VolumeBase.h b/model/VolumeBase.h
index 6532a80..92a83f0 100644
--- a/model/VolumeBase.h
+++ b/model/VolumeBase.h
@@ -54,6 +54,7 @@
         kEmulated,
         kAsec,
         kObb,
+        kStub,
     };
 
     enum MountFlags {