diff --git a/otautil/roots.cpp b/otautil/roots.cpp
new file mode 100644
index 0000000..815d644
--- /dev/null
+++ b/otautil/roots.cpp
@@ -0,0 +1,285 @@
+/*
+ * Copyright (C) 2007 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 "otautil/roots.h"
+
+#include <ctype.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/stringprintf.h>
+#include <android-base/unique_fd.h>
+#include <cryptfs.h>
+#include <ext4_utils/wipe.h>
+#include <fs_mgr.h>
+#include <fs_mgr/roots.h>
+#include <fs_mgr_dm_linear.h>
+
+#include "otautil/mounts.h"
+#include "otautil/sysutil.h"
+
+using android::fs_mgr::Fstab;
+using android::fs_mgr::FstabEntry;
+using android::fs_mgr::ReadDefaultFstab;
+
+static Fstab fstab;
+
+void load_volume_table() {
+  if (!ReadDefaultFstab(&fstab)) {
+    LOG(ERROR) << "Failed to read default fstab";
+    return;
+  }
+
+  fstab.emplace_back(FstabEntry{
+      .mount_point = "/tmp", .fs_type = "ramdisk", .blk_device = "ramdisk", .length = 0 });
+
+  std::cout << "recovery filesystem table" << std::endl << "=========================" << std::endl;
+  for (size_t i = 0; i < fstab.size(); ++i) {
+    const auto& entry = fstab[i];
+    std::cout << "  " << i << " " << entry.mount_point << " "
+              << " " << entry.fs_type << " " << entry.blk_device << " " << entry.length
+              << std::endl;
+  }
+  std::cout << std::endl;
+}
+
+Volume* volume_for_mount_point(const std::string& mount_point) {
+  return android::fs_mgr::GetEntryForMountPoint(&fstab, mount_point);
+}
+
+// Mount the volume specified by path at the given mount_point.
+int ensure_path_mounted_at(const std::string& path, const std::string& mount_point) {
+  return android::fs_mgr::EnsurePathMounted(&fstab, path, mount_point) ? 0 : -1;
+}
+
+int ensure_path_mounted(const std::string& path) {
+  // Mount at the default mount point.
+  return android::fs_mgr::EnsurePathMounted(&fstab, path) ? 0 : -1;
+}
+
+int ensure_path_unmounted(const std::string& path) {
+  return android::fs_mgr::EnsurePathUnmounted(&fstab, path) ? 0 : -1;
+}
+
+static int exec_cmd(const std::vector<std::string>& args) {
+  CHECK(!args.empty());
+  auto argv = StringVectorToNullTerminatedArray(args);
+
+  pid_t child;
+  if ((child = fork()) == 0) {
+    execv(argv[0], argv.data());
+    _exit(EXIT_FAILURE);
+  }
+
+  int status;
+  waitpid(child, &status, 0);
+  if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+    LOG(ERROR) << args[0] << " failed with status " << WEXITSTATUS(status);
+  }
+  return WEXITSTATUS(status);
+}
+
+static int64_t get_file_size(int fd, uint64_t reserve_len) {
+  struct stat buf;
+  int ret = fstat(fd, &buf);
+  if (ret) return 0;
+
+  int64_t computed_size;
+  if (S_ISREG(buf.st_mode)) {
+    computed_size = buf.st_size - reserve_len;
+  } else if (S_ISBLK(buf.st_mode)) {
+    uint64_t block_device_size = get_block_device_size(fd);
+    if (block_device_size < reserve_len ||
+        block_device_size > std::numeric_limits<int64_t>::max()) {
+      computed_size = 0;
+    } else {
+      computed_size = block_device_size - reserve_len;
+    }
+  } else {
+    computed_size = 0;
+  }
+
+  return computed_size;
+}
+
+int format_volume(const std::string& volume, const std::string& directory) {
+  const FstabEntry* v = android::fs_mgr::GetEntryForPath(&fstab, volume);
+  if (v == nullptr) {
+    LOG(ERROR) << "unknown volume \"" << volume << "\"";
+    return -1;
+  }
+  if (v->fs_type == "ramdisk") {
+    LOG(ERROR) << "can't format_volume \"" << volume << "\"";
+    return -1;
+  }
+  if (v->mount_point != volume) {
+    LOG(ERROR) << "can't give path \"" << volume << "\" to format_volume";
+    return -1;
+  }
+  if (ensure_path_unmounted(volume) != 0) {
+    LOG(ERROR) << "format_volume: Failed to unmount \"" << v->mount_point << "\"";
+    return -1;
+  }
+  if (v->fs_type != "ext4" && v->fs_type != "f2fs") {
+    LOG(ERROR) << "format_volume: fs_type \"" << v->fs_type << "\" unsupported";
+    return -1;
+  }
+
+  // If there's a key_loc that looks like a path, it should be a block device for storing encryption
+  // metadata. Wipe it too.
+  if (!v->key_loc.empty() && v->key_loc[0] == '/') {
+    LOG(INFO) << "Wiping " << v->key_loc;
+    int fd = open(v->key_loc.c_str(), O_WRONLY | O_CREAT, 0644);
+    if (fd == -1) {
+      PLOG(ERROR) << "format_volume: Failed to open " << v->key_loc;
+      return -1;
+    }
+    wipe_block_device(fd, get_file_size(fd));
+    close(fd);
+  }
+
+  int64_t length = 0;
+  if (v->length > 0) {
+    length = v->length;
+  } else if (v->length < 0 || v->key_loc == "footer") {
+    android::base::unique_fd fd(open(v->blk_device.c_str(), O_RDONLY));
+    if (fd == -1) {
+      PLOG(ERROR) << "format_volume: failed to open " << v->blk_device;
+      return -1;
+    }
+    length = get_file_size(fd.get(), v->length ? -v->length : CRYPT_FOOTER_OFFSET);
+    if (length <= 0) {
+      LOG(ERROR) << "get_file_size: invalid size " << length << " for " << v->blk_device;
+      return -1;
+    }
+  }
+
+  if (v->fs_type == "ext4") {
+    static constexpr int kBlockSize = 4096;
+    std::vector<std::string> mke2fs_args = {
+      "/system/bin/mke2fs", "-F", "-t", "ext4", "-b", std::to_string(kBlockSize),
+    };
+
+    int raid_stride = v->logical_blk_size / kBlockSize;
+    int raid_stripe_width = v->erase_blk_size / kBlockSize;
+    // stride should be the max of 8KB and logical block size
+    if (v->logical_blk_size != 0 && v->logical_blk_size < 8192) {
+      raid_stride = 8192 / kBlockSize;
+    }
+    if (v->erase_blk_size != 0 && v->logical_blk_size != 0) {
+      mke2fs_args.push_back("-E");
+      mke2fs_args.push_back(
+          android::base::StringPrintf("stride=%d,stripe-width=%d", raid_stride, raid_stripe_width));
+    }
+    mke2fs_args.push_back(v->blk_device);
+    if (length != 0) {
+      mke2fs_args.push_back(std::to_string(length / kBlockSize));
+    }
+
+    int result = exec_cmd(mke2fs_args);
+    if (result == 0 && !directory.empty()) {
+      std::vector<std::string> e2fsdroid_args = {
+        "/system/bin/e2fsdroid", "-e", "-f", directory, "-a", volume, v->blk_device,
+      };
+      result = exec_cmd(e2fsdroid_args);
+    }
+
+    if (result != 0) {
+      PLOG(ERROR) << "format_volume: Failed to make ext4 on " << v->blk_device;
+      return -1;
+    }
+    return 0;
+  }
+
+  // Has to be f2fs because we checked earlier.
+  static constexpr int kSectorSize = 4096;
+  std::vector<std::string> make_f2fs_cmd = {
+    "/system/bin/make_f2fs",
+    "-g",
+    "android",
+    v->blk_device,
+  };
+  if (length >= kSectorSize) {
+    make_f2fs_cmd.push_back(std::to_string(length / kSectorSize));
+  }
+
+  if (exec_cmd(make_f2fs_cmd) != 0) {
+    PLOG(ERROR) << "format_volume: Failed to make_f2fs on " << v->blk_device;
+    return -1;
+  }
+  if (!directory.empty()) {
+    std::vector<std::string> sload_f2fs_cmd = {
+      "/system/bin/sload_f2fs", "-f", directory, "-t", volume, v->blk_device,
+    };
+    if (exec_cmd(sload_f2fs_cmd) != 0) {
+      PLOG(ERROR) << "format_volume: Failed to sload_f2fs on " << v->blk_device;
+      return -1;
+    }
+  }
+  return 0;
+}
+
+int format_volume(const std::string& volume) {
+  return format_volume(volume, "");
+}
+
+int setup_install_mounts() {
+  if (fstab.empty()) {
+    LOG(ERROR) << "can't set up install mounts: no fstab loaded";
+    return -1;
+  }
+  for (const FstabEntry& entry : fstab) {
+    // We don't want to do anything with "/".
+    if (entry.mount_point == "/") {
+      continue;
+    }
+
+    if (entry.mount_point == "/tmp" || entry.mount_point == "/cache") {
+      if (ensure_path_mounted(entry.mount_point) != 0) {
+        LOG(ERROR) << "Failed to mount " << entry.mount_point;
+        return -1;
+      }
+    } else {
+      if (ensure_path_unmounted(entry.mount_point) != 0) {
+        LOG(ERROR) << "Failed to unmount " << entry.mount_point;
+        return -1;
+      }
+    }
+  }
+  return 0;
+}
+
+bool logical_partitions_mapped() {
+  return android::fs_mgr::LogicalPartitionsMapped();
+}
+
+std::string get_system_root() {
+  return android::fs_mgr::GetSystemRoot();
+}