diff --git a/filesystem_copier_action.cc b/filesystem_copier_action.cc
new file mode 100644
index 0000000..875df95
--- /dev/null
+++ b/filesystem_copier_action.cc
@@ -0,0 +1,305 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "update_engine/filesystem_copier_action.h"
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <algorithm>
+#include <string>
+#include <vector>
+#include "update_engine/filesystem_iterator.h"
+#include "update_engine/subprocess.h"
+#include "update_engine/utils.h"
+
+using std::min;
+using std::string;
+using std::vector;
+
+namespace chromeos_update_engine {
+
+namespace {
+const char* kMountpointTemplate = "/tmp/au_dest_mnt.XXXXXX";
+const off_t kCopyFileBufferSize = 4 * 1024 * 1024;
+const char* kCopyExclusionPrefix = "/lost+found";
+}  // namespace {}
+
+void FilesystemCopierAction::PerformAction() {
+  if (!HasInputObject()) {
+    LOG(ERROR) << "No input object. Aborting.";
+    processor_->ActionComplete(this, false);
+    return;
+  }
+  install_plan_ = GetInputObject();
+
+  if (install_plan_.is_full_update) {
+    // No copy needed.
+    processor_->ActionComplete(this, true);
+    return;
+  }
+
+  {
+    // Set up dest_path_
+    char *dest_path_temp = strdup(kMountpointTemplate);
+    CHECK(dest_path_temp);
+    CHECK_EQ(mkdtemp(dest_path_temp), dest_path_temp);
+    CHECK_NE(dest_path_temp[0], '\0');
+    dest_path_ = dest_path_temp;
+    free(dest_path_temp);
+  }
+
+  // Make sure we're properly mounted
+  if (Mount(install_plan_.install_path, dest_path_)) {
+    bool done_early = false;
+    if (utils::FileExists(
+            (dest_path_ +
+             FilesystemCopierAction::kCompleteFilesystemMarker).c_str())) {
+      // We're done!
+      done_early = true;
+      skipped_copy_ = true;
+      if (HasOutputPipe())
+        SetOutputObject(install_plan_);
+    }
+    if (!Unmount(dest_path_)) {
+      LOG(ERROR) << "Unmount failed. Aborting.";
+      processor_->ActionComplete(this, false);
+      return;
+    }
+    if (done_early) {
+      CHECK(!is_mounted_);
+      if (rmdir(dest_path_.c_str()) != 0)
+        LOG(ERROR) << "Unable to remove " << dest_path_;
+      processor_->ActionComplete(this, true);
+      return;
+    }
+  }
+  LOG(ERROR) << "not mounted; spawning thread";
+  // If we get here, mount failed or we're not done yet. Reformat and copy.
+  CHECK_EQ(pthread_create(&helper_thread_, NULL, HelperThreadMainStatic, this),
+           0);
+}
+
+void FilesystemCopierAction::TerminateProcessing() {
+  if (is_mounted_) {
+    LOG(ERROR) << "Aborted processing, but left a filesystem mounted.";
+  }
+}
+
+bool FilesystemCopierAction::Mount(const string& device,
+                                   const string& mountpoint) {
+  CHECK(!is_mounted_);
+  if(utils::MountFilesystem(device, mountpoint))
+    is_mounted_ = true;
+  return is_mounted_;
+}
+
+bool FilesystemCopierAction::Unmount(const string& mountpoint) {
+  CHECK(is_mounted_);
+  if (utils::UnmountFilesystem(mountpoint))
+    is_mounted_ = false;
+  return !is_mounted_;
+}
+
+void* FilesystemCopierAction::HelperThreadMain() {
+  // First, format the drive
+  vector<string> cmd;
+  cmd.push_back("/sbin/mkfs.ext3");
+  cmd.push_back("-F");
+  cmd.push_back(install_plan_.install_path);
+  int return_code = 1;
+  bool success = Subprocess::SynchronousExec(cmd, &return_code);
+  if (return_code != 0) {
+    LOG(INFO) << "Format of " << install_plan_.install_path
+              << " failed. Exit code: " << return_code;
+    success = false;
+  }
+  if (success) {
+    if (!Mount(install_plan_.install_path, dest_path_)) {
+      LOG(ERROR) << "Mount failed. Aborting";
+      success = false;
+    }
+  }
+  if (success) {
+    success = CopySynchronously();
+  }
+  if (success) {
+    // Place our marker to avoid copies again in the future
+    int r = open((dest_path_ +
+                  FilesystemCopierAction::kCompleteFilesystemMarker).c_str(),
+                 O_CREAT | O_WRONLY, 0644);
+    if (r >= 0)
+      close(r);
+  }
+  // Unmount
+  if (!Unmount(dest_path_)) {
+    LOG(ERROR) << "Unmount failed. Aborting";
+    success = false;
+  }
+  if (HasOutputPipe())
+    SetOutputObject(install_plan_);
+
+  // Tell main thread that we're done
+  g_timeout_add(0, CollectThreadStatic, this);
+  return reinterpret_cast<void*>(success ? 0 : 1);
+}
+
+void FilesystemCopierAction::CollectThread() {
+  void *thread_ret_value = NULL;
+  CHECK_EQ(pthread_join(helper_thread_, &thread_ret_value), 0);
+  bool success = (thread_ret_value == 0);
+  CHECK(!is_mounted_);
+  if (rmdir(dest_path_.c_str()) != 0)
+    LOG(INFO) << "Unable to remove " << dest_path_;
+  LOG(INFO) << "FilesystemCopierAction done";
+  processor_->ActionComplete(this, success);
+}
+
+bool FilesystemCopierAction::CreateDirSynchronously(const std::string& new_path,
+                                                    const struct stat& stbuf) {
+  int r = mkdir(new_path.c_str(), stbuf.st_mode);
+  TEST_AND_RETURN_FALSE_ERRNO(r == 0);
+  return true;
+}
+
+bool FilesystemCopierAction::CopyFileSynchronously(const std::string& old_path,
+                                                   const std::string& new_path,
+                                                   const struct stat& stbuf) {
+  int fd_out = open(new_path.c_str(), O_CREAT | O_EXCL | O_WRONLY,
+                    stbuf.st_mode);
+  TEST_AND_RETURN_FALSE_ERRNO(fd_out >= 0);
+  ScopedFdCloser fd_out_closer(&fd_out);
+  int fd_in = open(old_path.c_str(), O_RDONLY, 0);
+  TEST_AND_RETURN_FALSE_ERRNO(fd_in >= 0);
+  ScopedFdCloser fd_in_closer(&fd_in);
+
+  vector<char> buf(min(kCopyFileBufferSize, stbuf.st_size));
+  off_t bytes_written = 0;
+  while (true) {
+    // Make sure we don't need to abort early:
+    TEST_AND_RETURN_FALSE(!g_atomic_int_get(&thread_should_exit_));
+
+    ssize_t read_size = read(fd_in, &buf[0], buf.size());
+    TEST_AND_RETURN_FALSE_ERRNO(read_size >= 0);
+    if (0 == read_size)  // EOF
+      break;
+
+    ssize_t write_size = 0;
+    while (write_size < read_size) {
+      ssize_t r = write(fd_out, &buf[write_size], read_size - write_size);
+      TEST_AND_RETURN_FALSE_ERRNO(r >= 0);
+      write_size += r;
+    }
+    CHECK_EQ(write_size, read_size);
+    bytes_written += write_size;
+    CHECK_LE(bytes_written, stbuf.st_size);
+    if (bytes_written == stbuf.st_size)
+      break;
+  }
+  CHECK_EQ(bytes_written, stbuf.st_size);
+  return true;
+}
+
+bool FilesystemCopierAction::CreateHardLinkSynchronously(
+    const std::string& old_path,
+    const std::string& new_path) {
+  int r = link(old_path.c_str(), new_path.c_str());
+  TEST_AND_RETURN_FALSE_ERRNO(r == 0);
+  return true;
+}
+
+bool FilesystemCopierAction::CopySymlinkSynchronously(
+    const std::string& old_path,
+    const std::string& new_path,
+    const struct stat& stbuf) {
+  vector<char> buf(PATH_MAX + 1);
+  ssize_t r = readlink(old_path.c_str(), &buf[0], buf.size());
+  TEST_AND_RETURN_FALSE_ERRNO(r >= 0);
+  // Make sure we got the entire link
+  TEST_AND_RETURN_FALSE(static_cast<unsigned>(r) < buf.size());
+  buf[r] = '\0';
+  int rc = symlink(&buf[0], new_path.c_str());
+  TEST_AND_RETURN_FALSE_ERRNO(rc == 0);
+  return true;
+}
+
+bool FilesystemCopierAction::CreateNodeSynchronously(
+    const std::string& new_path,
+    const struct stat& stbuf) {
+  int r = mknod(new_path.c_str(), stbuf.st_mode, stbuf.st_rdev);
+  TEST_AND_RETURN_FALSE_ERRNO(r == 0);
+  return true;
+}
+
+// Returns true on success
+bool FilesystemCopierAction::CopySynchronously() {
+  // This map is a map from inode # to new_path.
+  map<ino_t, string> hard_links;
+  FilesystemIterator iter(copy_source_,
+                          utils::SetWithValue<string>(kCopyExclusionPrefix));
+  bool success = true;
+  for (; !g_atomic_int_get(&thread_should_exit_) &&
+           !iter.IsEnd(); iter.Increment()) {
+    const string old_path = iter.GetFullPath();
+    const string new_path = dest_path_ + iter.GetPartialPath();
+    LOG(INFO) << "copying " << old_path << " to " << new_path;
+    const struct stat stbuf = iter.GetStat();
+    success = false;
+
+    // Skip lost+found
+    CHECK_NE(kCopyExclusionPrefix, iter.GetPartialPath());
+
+    // Directories can't be hard-linked, so check for directories first
+    if (iter.GetPartialPath().empty()) {
+      // Root has an empty path.
+      // We don't need to create anything for the root, which is the first
+      // thing we get from the iterator.
+      success = true;
+    } else if (S_ISDIR(stbuf.st_mode)) {
+      success = CreateDirSynchronously(new_path, stbuf);
+    } else {
+      if (stbuf.st_nlink > 1 &&
+          utils::MapContainsKey(hard_links, stbuf.st_ino)) {
+        success = CreateHardLinkSynchronously(hard_links[stbuf.st_ino],
+                                              new_path);
+      } else {
+        if (stbuf.st_nlink > 1)
+          hard_links[stbuf.st_ino] = new_path;
+        if (S_ISREG(stbuf.st_mode)) {
+          success = CopyFileSynchronously(old_path, new_path, stbuf);
+        } else if (S_ISLNK(stbuf.st_mode)) {
+          success = CopySymlinkSynchronously(old_path, new_path, stbuf);
+        } else if (S_ISFIFO(stbuf.st_mode) ||
+                   S_ISCHR(stbuf.st_mode) ||
+                   S_ISBLK(stbuf.st_mode) ||
+                   S_ISSOCK(stbuf.st_mode)) {
+          success = CreateNodeSynchronously(new_path, stbuf);
+        } else {
+          CHECK(false) << "Unable to copy file " << old_path << " with mode "
+                       << stbuf.st_mode;
+        }
+      }
+    }
+    TEST_AND_RETURN_FALSE(success);
+
+    // chmod new file
+    if (!S_ISLNK(stbuf.st_mode)) {
+      int r = chmod(new_path.c_str(), stbuf.st_mode);
+      TEST_AND_RETURN_FALSE_ERRNO(r == 0);
+    }
+
+    // Set uid/gid.
+    int r = lchown(new_path.c_str(), stbuf.st_uid, stbuf.st_gid);
+    TEST_AND_RETURN_FALSE_ERRNO(r == 0);
+  }
+  TEST_AND_RETURN_FALSE(!iter.IsErr());
+  // Success!
+  return true;
+}
+
+const char* FilesystemCopierAction::kCompleteFilesystemMarker(
+    "/update_engine_copy_success");
+
+}  // namespace chromeos_update_engine