diff --git a/fs_mgr/Android.bp b/fs_mgr/Android.bp
index 974e13e..a476cd8 100644
--- a/fs_mgr/Android.bp
+++ b/fs_mgr/Android.bp
@@ -111,3 +111,26 @@
         "libgsi_headers",
     ],
 }
+
+cc_binary {
+    name: "remount",
+    defaults: ["fs_mgr_defaults"],
+    shared_libs: [
+        "libbase",
+        "libfs_mgr",
+    ],
+    srcs: [
+        "fs_mgr_remount.cpp",
+    ],
+    cppflags: [
+        "-DALLOW_ADBD_DISABLE_VERITY=0",
+    ],
+    product_variables: {
+        debuggable: {
+            cppflags: [
+                "-UALLOW_ADBD_DISABLE_VERITY",
+                "-DALLOW_ADBD_DISABLE_VERITY=1",
+            ],
+        },
+    },
+}
diff --git a/fs_mgr/fs_mgr_remount.cpp b/fs_mgr/fs_mgr_remount.cpp
new file mode 100644
index 0000000..66756ab
--- /dev/null
+++ b/fs_mgr/fs_mgr_remount.cpp
@@ -0,0 +1,281 @@
+/*
+ * Copyright (C) 2019 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 <errno.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <unistd.h>
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/strings.h>
+#include <fs_mgr_overlayfs.h>
+#include <fs_mgr_priv.h>
+#include <fstab/fstab.h>
+
+namespace {
+
+[[noreturn]] void usage(int exit_status) {
+    LOG(INFO) << getprogname()
+              << " [-h]\n"
+                 "\t-h --help\tthis help\n"
+                 "\n"
+                 "Remount all partitions read-write.\n"
+                 "Verity must be disabled.";
+
+    ::exit(exit_status);
+}
+
+bool remountable_partition(const android::fs_mgr::FstabEntry& entry) {
+    if (entry.fs_mgr_flags.vold_managed) return false;
+    if (entry.fs_mgr_flags.recovery_only) return false;
+    if (entry.fs_mgr_flags.slot_select_other) return false;
+    if (!(entry.flags & MS_RDONLY)) return false;
+    if (entry.fs_type == "vfat") return false;
+    return true;
+}
+
+const std::string system_mount_point(const android::fs_mgr::FstabEntry& entry) {
+    if (entry.mount_point == "/") return "/system";
+    return entry.mount_point;
+}
+
+const android::fs_mgr::FstabEntry* is_wrapped(const android::fs_mgr::Fstab& overlayfs_candidates,
+                                              const android::fs_mgr::FstabEntry& entry) {
+    auto mount_point = system_mount_point(entry);
+    auto it = std::find_if(overlayfs_candidates.begin(), overlayfs_candidates.end(),
+                           [&mount_point](const auto& entry) {
+                               return android::base::StartsWith(mount_point,
+                                                                system_mount_point(entry) + "/");
+                           });
+    if (it == overlayfs_candidates.end()) return nullptr;
+    return &(*it);
+}
+
+void try_unmount_bionic(android::fs_mgr::Fstab* mounts) {
+    static constexpr const char* kBionic = "/bionic";
+
+    auto entry = GetEntryForMountPoint(mounts, kBionic);
+    if (!entry) return;
+
+    struct statfs buf;
+    if (::statfs(kBionic, &buf) == -1) {
+        PLOG(ERROR) << "statfs of " << kBionic;
+        return;
+    }
+    if (buf.f_flags & MS_RDONLY) {
+        // /bionic is on a read-only partition; can happen for
+        // non-system-as-root-devices. Don' try to unmount.
+        return;
+    }
+    fs_mgr_set_blk_ro(entry->blk_device, false);
+    if (::mount(entry->blk_device.c_str(), entry->mount_point.c_str(), entry->fs_type.c_str(),
+                MS_REMOUNT, nullptr) == -1) {
+        PLOG(ERROR) << "remount of " << kBionic;
+    }
+}
+
+void MyLogger(android::base::LogId, android::base::LogSeverity severity, const char*, const char*,
+              unsigned int, const char* message) {
+    static const char log_characters[] = "VD\0WEFF";
+    if (severity < sizeof(log_characters)) {
+        auto severity_char = log_characters[severity];
+        if (severity_char) fprintf(stderr, "%c ", severity_char);
+    }
+    fprintf(stderr, "%s\n", message);
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+    android::base::InitLogging(argv, MyLogger);
+
+    enum {
+        SUCCESS,
+        NOT_USERDEBUG,
+        BADARG,
+        NOT_ROOT,
+        NO_FSTAB,
+        VERITY_PARTITION,
+        BAD_OVERLAY,
+        NO_MOUNTS,
+        REMOUNT_FAILED,
+    } retval = SUCCESS;
+
+    // If somehow this executable is delivered on a "user" build, it can
+    // not function, so providing a clear message to the caller rather than
+    // letting if fall through and provide a lot of confusing failure messages.
+    if (!ALLOW_ADBD_DISABLE_VERITY || (android::base::GetProperty("ro.debuggable", "0") != "1")) {
+        LOG(ERROR) << "only functions on userdebug or eng builds";
+        return NOT_USERDEBUG;
+    }
+
+    struct option longopts[] = {
+            {"help", no_argument, nullptr, 'h'},
+            {0, 0, nullptr, 0},
+    };
+    for (int opt; (opt = ::getopt_long(argc, argv, "h", longopts, nullptr)) != -1;) {
+        switch (opt) {
+            default:
+                LOG(ERROR) << "Bad Argument -" << char(opt);
+                usage(BADARG);
+                break;
+            case 'h':
+                usage(SUCCESS);
+                break;
+        }
+    }
+
+    if (argc > optind) {
+        LOG(ERROR) << "Bad Argument " << argv[optind];
+        usage(BADARG);
+    }
+
+    // Make sure we are root.
+    if (::getuid() != 0) {
+        LOG(ERROR) << "must be run as root";
+        return NOT_ROOT;
+    }
+
+    android::fs_mgr::Fstab fstab;
+    auto fstab_read = android::fs_mgr::ReadDefaultFstab(&fstab);
+    if (!fstab_read || fstab.empty()) {
+        PLOG(ERROR) << "Failed to read default fstab";
+        return NO_FSTAB;
+    }
+
+    // Generate the list of supported overlayfs mount points.
+    auto overlayfs_candidates = fs_mgr_overlayfs_candidate_list(fstab);
+
+    // Generate the all remountable partitions sub-list
+    android::fs_mgr::Fstab partitions;
+    for (auto const& entry : fstab) {
+        if (!remountable_partition(entry)) continue;
+        if (overlayfs_candidates.empty() ||
+            GetEntryForMountPoint(&overlayfs_candidates, entry.mount_point) ||
+            (is_wrapped(overlayfs_candidates, entry) == nullptr)) {
+            partitions.emplace_back(entry);
+        }
+    }
+
+    // Check verity and optionally setup overlayfs backing.
+    for (auto it = partitions.begin(); it != partitions.end();) {
+        auto& entry = *it;
+        auto& mount_point = entry.mount_point;
+        if (fs_mgr_is_verity_enabled(entry)) {
+            LOG(ERROR) << "Verity enabled on " << mount_point << ", skipping";
+            retval = VERITY_PARTITION;
+            it = partitions.erase(it);
+            continue;
+        }
+
+        auto change = false;
+        errno = 0;
+        if (fs_mgr_overlayfs_setup(nullptr, mount_point.c_str(), &change)) {
+            if (change) {
+                LOG(INFO) << "Using overlayfs for " << mount_point;
+            }
+        } else if (errno) {
+            PLOG(ERROR) << "Overlayfs setup for " << mount_point << " failed, skipping";
+            retval = BAD_OVERLAY;
+            it = partitions.erase(it);
+            continue;
+        }
+        ++it;
+    }
+
+    if (partitions.empty()) {
+        LOG(WARNING) << "No partitions to remount";
+        return retval;
+    }
+
+    // Mount overlayfs.
+    if (!fs_mgr_overlayfs_mount_all(&partitions)) {
+        retval = BAD_OVERLAY;
+        PLOG(ERROR) << "Can not mount overlayfs for partitions";
+    }
+
+    // Get actual mounts _after_ overlayfs has been added.
+    android::fs_mgr::Fstab mounts;
+    if (!android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts) || mounts.empty()) {
+        PLOG(ERROR) << "Failed to read /proc/mounts";
+        retval = NO_MOUNTS;
+    }
+
+    // Remount selected partitions.
+    for (auto& entry : partitions) {
+        // unlock the r/o key for the mount point device
+        if (entry.fs_mgr_flags.logical) {
+            fs_mgr_update_logical_partition(&entry);
+        }
+        auto blk_device = entry.blk_device;
+        auto mount_point = entry.mount_point;
+
+        for (auto it = mounts.rbegin(); it != mounts.rend(); ++it) {
+            auto& rentry = *it;
+            if (mount_point == rentry.mount_point) {
+                blk_device = rentry.blk_device;
+                break;
+            }
+            if ((mount_point == "/") && (rentry.mount_point == "/system")) {
+                if (blk_device != "/dev/root") blk_device = rentry.blk_device;
+                mount_point = "/system";
+                break;
+            }
+        }
+        fs_mgr_set_blk_ro(blk_device, false);
+
+        // Now remount!
+        if (::mount(blk_device.c_str(), mount_point.c_str(), entry.fs_type.c_str(), MS_REMOUNT,
+                    nullptr) == 0) {
+            continue;
+        }
+        if ((errno == EINVAL) && (mount_point != entry.mount_point)) {
+            mount_point = entry.mount_point;
+            if (::mount(blk_device.c_str(), mount_point.c_str(), entry.fs_type.c_str(), MS_REMOUNT,
+                        nullptr) == 0) {
+                continue;
+            }
+        }
+        // If errno = EROFS at this point, we are dealing with r/o
+        // filesystem types like squashfs, erofs or ext4 dedupe. We will
+        // consider such a device that does not have CONFIG_OVERLAY_FS
+        // in the kernel as a misconfigured and take no action.
+        //
+        // ext4 dedupe _can_ be worked around by performing a reboot into
+        // recovery and fsck'ing.  However the current decision is to not
+        // reboot to reserve only one shell command to do so (reboot).  In
+        // the future, if this is a problem, a -R flag could be introduced
+        // to give permission to do so and as a convenience also implement
+        // verity disable operations.  We will require this functionality
+        // in order for adb remount to call this executable instead of its
+        // current internal code that recognizes the -R flag and logistics.
+        PLOG(ERROR) << "failed to remount partition dev:" << blk_device << " mnt:" << mount_point;
+        retval = REMOUNT_FAILED;
+    }
+
+    try_unmount_bionic(&mounts);
+
+    return retval;
+}
diff --git a/fs_mgr/tests/adb-remount-test.sh b/fs_mgr/tests/adb-remount-test.sh
index bbe80ab..1956215 100755
--- a/fs_mgr/tests/adb-remount-test.sh
+++ b/fs_mgr/tests/adb-remount-test.sh
@@ -1140,6 +1140,36 @@
   die "/vendor is not read-write"
 echo "${GREEN}[       OK ]${NORMAL} mount -o rw,remount command works" >&2
 
+# Prerequisite is a prepped device from above.
+adb_reboot &&
+  adb_wait 2m ||
+  die "lost device after reboot to ro state (USB stack broken?)"
+adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null &&
+  die "/vendor is not read-only"
+adb_su remount </dev/null ||
+  die "remount command"
+adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null ||
+  die "/vendor is not read-write"
+echo "${GREEN}[       OK ]${NORMAL} remount command works from setup" >&2
+
+# Prerequisite is an overlayfs deconstructed device but with verity disabled.
+# This also saves a lot of 'noise' from the command doing a mkfs on backing
+# storage and all the related tuning and adjustment.
+for d in ${OVERLAYFS_BACKING}; do
+  adb_su rm -rf /${d}/overlay </dev/null ||
+    die "/${d}/overlay wipe"
+done
+adb_reboot &&
+  adb_wait 2m ||
+  die "lost device after reboot after wipe (USB stack broken?)"
+adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null &&
+  die "/vendor is not read-only"
+adb_su remount </dev/null ||
+  die "remount command"
+adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null ||
+  die "/vendor is not read-write"
+echo "${GREEN}[       OK ]${NORMAL} remount command works from scratch" >&2
+
 restore
 err=${?}