diff --git a/compositediskconfig/src/lib.rs b/compositediskconfig/src/lib.rs
index 3546dd3..dc199e4 100644
--- a/compositediskconfig/src/lib.rs
+++ b/compositediskconfig/src/lib.rs
@@ -15,7 +15,6 @@
 //! JSON configuration for composite disks, as used for running `mk_cdisk` and by the `vm` tool.
 
 use serde::{Deserialize, Serialize};
-use std::io::Write;
 use std::path::PathBuf;
 
 /// Configuration for running `mk_cdisk`.
@@ -36,10 +35,3 @@
     #[serde(default)]
     pub writable: bool,
 }
-
-impl Config {
-    /// Write the configuration as JSON, in the format used by `mk_cdisk`.
-    pub fn write_json(&self, writer: impl Write) -> serde_json::Result<()> {
-        serde_json::to_writer(writer, self)
-    }
-}
diff --git a/microdroid/payload/metadata/Android.bp b/microdroid/payload/metadata/Android.bp
new file mode 100644
index 0000000..4b23394
--- /dev/null
+++ b/microdroid/payload/metadata/Android.bp
@@ -0,0 +1,16 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+rust_library {
+    name: "libmicrodroid_metadata",
+    host_supported: true,
+    crate_name: "microdroid_metadata",
+    srcs: ["src/lib.rs"],
+    prefer_rlib: true,
+    edition: "2018",
+    rustlibs: [
+        "libmicrodroid_metadata_proto_rust",
+        "libprotobuf",
+    ],
+}
diff --git a/microdroid/payload/metadata/src/lib.rs b/microdroid/payload/metadata/src/lib.rs
new file mode 100644
index 0000000..9c97411
--- /dev/null
+++ b/microdroid/payload/metadata/src/lib.rs
@@ -0,0 +1,42 @@
+// Copyright 2021, 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.
+
+//! Read/write metadata blob for VM payload image. The blob is supposed to be used as a metadata
+//! partition in the VM payload image.
+//! The layout of metadata blob is like:
+//!   4 bytes : size(N) in big endian
+//!   N bytes : protobuf message for Metadata
+
+use protobuf::Message;
+use std::io;
+use std::io::Read;
+use std::io::Write;
+
+pub use microdroid_metadata::metadata::{ApexPayload, ApkPayload, Metadata};
+
+/// Reads a metadata from a reader
+pub fn read_metadata<T: Read>(mut r: T) -> io::Result<Metadata> {
+    let mut buf = [0u8; 4];
+    r.read_exact(&mut buf)?;
+    let size = i32::from_be_bytes(buf);
+    Ok(Metadata::parse_from_reader(&mut r.take(size as u64))?)
+}
+
+/// Writes a metadata to a writer
+pub fn write_metadata<T: Write>(metadata: &Metadata, mut w: T) -> io::Result<()> {
+    let mut buf = Vec::new();
+    metadata.write_to_writer(&mut buf)?;
+    w.write_all(&(buf.len() as i32).to_be_bytes())?;
+    w.write_all(&buf)
+}
diff --git a/microdroid_manager/Android.bp b/microdroid_manager/Android.bp
index 5cf94a1..267147f 100644
--- a/microdroid_manager/Android.bp
+++ b/microdroid_manager/Android.bp
@@ -13,7 +13,7 @@
         "libkernlog",
         "libkeystore2_system_property-rust",
         "liblog_rust",
-        "libmicrodroid_metadata_proto_rust",
+        "libmicrodroid_metadata",
         "libmicrodroid_payload_config",
         "libprotobuf",
         "libserde",
diff --git a/microdroid_manager/src/metadata.rs b/microdroid_manager/src/metadata.rs
index 4f7d7af..81d9cc4 100644
--- a/microdroid_manager/src/metadata.rs
+++ b/microdroid_manager/src/metadata.rs
@@ -15,25 +15,14 @@
 //! Payload metadata from /dev/block/by-name/metadata
 
 use log::info;
-use microdroid_metadata::metadata::Metadata;
-use protobuf::Message;
+use microdroid_metadata::{read_metadata, Metadata};
 use std::fs::File;
 use std::io;
-use std::io::Read;
 
 const METADATA_PATH: &str = "/dev/block/by-name/metadata";
 
 /// loads payload metadata from /dev/block/by-name/metadata
 pub fn load() -> io::Result<Metadata> {
     info!("loading payload metadata...");
-
-    let mut f = File::open(METADATA_PATH)?;
-    // metadata partition is
-    //  4 bytes : size(N) in big endian
-    //  N bytes : message for Metadata
-    let mut buf = [0u8; 4];
-    f.read_exact(&mut buf)?;
-    let size = i32::from_be_bytes(buf);
-
-    Ok(Metadata::parse_from_reader(&mut f.take(size as u64))?)
+    read_metadata(File::open(METADATA_PATH)?)
 }