diff --git a/build_image b/build_image
index a64261d11a..d6e2cba551 100755
--- a/build_image
+++ b/build_image
@@ -22,8 +22,6 @@ DEFAULT_GROUP=developer
 # Developer-visible flags.
 DEFINE_string board "${DEFAULT_BOARD}" \
   "The board to build an image for."
-DEFINE_string boot_args "" \
-  "Additional boot arguments to pass to the commandline"
 DEFINE_boolean enable_rootfs_verification ${FLAGS_TRUE} \
   "Default all bootloaders to use kernel-based root fs integrity checking."
 DEFINE_string output_root "${DEFAULT_BUILD_ROOT}/images" \
diff --git a/build_library/build_image_util.sh b/build_library/build_image_util.sh
index e8e1b760e6..e08414bac3 100755
--- a/build_library/build_image_util.sh
+++ b/build_library/build_image_util.sh
@@ -242,11 +242,7 @@ finish_image() {
   if mountpoint -q "${root_fs_dir}"/boot; then
     install_grub=1
     ${BUILD_LIBRARY_DIR}/configure_bootloaders.sh \
-      --arch=${ARCH} \
-      --disk_layout="${disk_layout}" \
-      --boot_dir="${root_fs_dir}"/usr/boot \
-      --esp_dir="${root_fs_dir}"/boot \
-      --boot_args="${FLAGS_boot_args}"
+      --boot_dir="${root_fs_dir}"/usr/boot
   fi
 
   if [[ -n "${FLAGS_developer_data}" ]]; then
@@ -273,7 +269,7 @@ finish_image() {
   # This script must mount the ESP partition differently, so run it after unmount
   if [[ "${install_grub}" -eq 1 ]]; then
     local target
-    for target in i386-pc x86_64-efi; do
+    for target in i386-pc x86_64-efi x86_64-xen; do
       ${BUILD_LIBRARY_DIR}/grub_install.sh \
           --target="${target}" --disk_image="${disk_img}"
     done
diff --git a/build_library/configure_bootloaders.sh b/build_library/configure_bootloaders.sh
index 09470c6f53..27b862cbec 100755
--- a/build_library/configure_bootloaders.sh
+++ b/build_library/configure_bootloaders.sh
@@ -4,8 +4,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# Helper script to generate GRUB bootloader configuration files for
-# x86 platforms.
+# Helper script to generate bootloader configuration files for systems
+# that predate our new GRUB2 based gptprio bootloader.
 
 SCRIPT_ROOT=$(readlink -f $(dirname "$0")/..)
 . "${SCRIPT_ROOT}/common.sh" || exit 1
@@ -14,16 +14,8 @@ SCRIPT_ROOT=$(readlink -f $(dirname "$0")/..)
 assert_inside_chroot
 
 # Flags.
-DEFINE_string arch "x86" \
-  "The boot architecture: arm or x86. (Default: x86)"
 DEFINE_string boot_dir "/tmp/boot" \
   "Path to boot directory in root filesystem (Default: /tmp/boot)"
-DEFINE_string esp_dir "" \
-  "Path to ESP partition mount point (Default: none)"
-DEFINE_string boot_args "" \
-  "Additional boot arguments to pass to the commandline (Default: '')"
-DEFINE_string disk_layout "base" \
-  "The disk layout type to use for this image."
 
 # Parse flags
 FLAGS "$@" || exit 1
@@ -34,17 +26,10 @@ switch_to_strict_mode
 common_args="console=tty0 ro noswap cros_legacy"
 common_args="${common_args} ${FLAGS_boot_args}"
 
-# Get partition UUIDs from the json config
-get_uuid() {
-  "${BUILD_LIBRARY_DIR}/disk_util" --disk_layout="${FLAGS_disk_layout}" \
-      readuuid "$1"
-}
-
 # Filesystem command line args.
 root_args="root=LABEL=ROOT rootflags=subvol=root"
-gptprio_args="${root_args} usr=gptprio:"
-slot_a_args="${root_args} usr=PARTUUID=$(get_uuid USR-A)"
-slot_b_args="${root_args} usr=PARTUUID=$(get_uuid USR-B)"
+slot_a_args="${root_args} usr=PARTLABEL=USR-A"
+slot_b_args="${root_args} usr=PARTLABEL=USR-B"
 
 GRUB_DIR="${FLAGS_boot_dir}/grub"
 SYSLINUX_DIR="${FLAGS_boot_dir}/syslinux"
@@ -73,11 +58,6 @@ EOF
 default         1
 $(< "${GRUB_DIR}/menu.lst.A")
 EOF
-  sudo cp "${GRUB_DIR}/menu.lst.A" "${GRUB_DIR}/menu.lst"
-
-  # menu.lst needs to go under boot/grub so pvgrub can find it reliably
-  sudo mkdir -p "${FLAGS_esp_dir}/boot/grub"
-  sudo cp "${GRUB_DIR}/menu.lst" "${FLAGS_esp_dir}/boot/grub"
 }
 
 # Build configuration files for syslinux
@@ -87,45 +67,11 @@ configure_syslinux() {
 
   # Add ttyS0 as a secondary console, useful for qemu -nographic
   # This leaves /dev/console mapped to tty0 (vga) which is reasonable default.
-  if [[ ${common_args} == *console=ttyS* ]] ; then
-    syslinux_args="${common_args}"
-  else
-    syslinux_args="console=ttyS0,115200n8 ${common_args}"
-  fi
+  syslinux_args="console=ttyS0,115200n8 ${common_args}"
 
-  sudo_clobber "${SYSLINUX_DIR}/syslinux.cfg" <<EOF
-PROMPT 1
-# display boot: prompt for a half second
-TIMEOUT 5
-# never sit at the prompt longer than a minute
-TOTALTIMEOUT 600
-
-# controls which kernel is the default
-include /syslinux/default.cfg
-
-include /syslinux/boot_kernel.cfg
-
-# coreos.A
-include /syslinux/root.A.cfg
-
-# coreos.B
-include /syslinux/root.B.cfg
-EOF
-
-  sudo_clobber "${SYSLINUX_DIR}/default.cfg" <<<"DEFAULT boot_kernel"
   sudo_clobber "${SYSLINUX_DIR}/default.cfg.A" <<<"DEFAULT coreos.A"
   sudo_clobber "${SYSLINUX_DIR}/default.cfg.B" <<<"DEFAULT coreos.B"
 
-  # Different files are used so that the updater can only touch the file it
-  # needs to for a given change.  This will minimize any potential accidental
-  # updates issues, hopefully.
-  sudo_clobber "${SYSLINUX_DIR}/boot_kernel.cfg" <<EOF
-label boot_kernel
-  menu label boot_kernel
-  kernel vmlinuz-boot_kernel
-  append ${syslinux_args} ${gptprio_args}
-EOF
-
   sudo_clobber "${SYSLINUX_DIR}/root.A.cfg" <<EOF
 label coreos.A
   menu label coreos.A
@@ -139,21 +85,7 @@ label coreos.B
   kernel vmlinuz.B
   append ${syslinux_args} ${slot_b_args}
 EOF
-
-  sudo cp -r "${SYSLINUX_DIR}/." "${FLAGS_esp_dir}/syslinux"
-
-  # Stage all kernels with the only one we built.
-  for kernel in syslinux/{vmlinuz-boot_kernel,vmlinuz.A,vmlinuz.B}
-  do
-    sudo cp "${FLAGS_boot_dir}/vmlinuz" "${FLAGS_esp_dir}/${kernel}"
-  done
 }
 
-[[ -d "${FLAGS_esp_dir}" ]] || die_notrace "--esp_dir is required"
-
-if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64"  ]]; then
-  configure_pvgrub
-  configure_syslinux
-else
-  error "No bootloader configuration for ${FLAGS_arch}"
-fi
+configure_pvgrub
+configure_syslinux
diff --git a/build_library/grub.cfg b/build_library/grub.cfg
index 1dfc1e50aa..c1ace553d4 100644
--- a/build_library/grub.cfg
+++ b/build_library/grub.cfg
@@ -1,13 +1,75 @@
+# Main GRUB config
+
 # Load any and all video drivers.
 # Required under UEFI to boot Linux with a working console.
 insmod all_video
 
-# Use both default text console and ttyS0
-serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
-terminal_input console serial
-terminal_output console serial
+# Default menuentry id and boot timeout
+set default="coreos"
+set timeout=1
 
-# Re-use the existing syslinux configuration
-echo "Loading SYSLINUX configuration..."
-insmod syslinuxcfg
-syslinux_source -s /syslinux/syslinux.cfg
+# Default kernel args for root filesystem and console.
+set linux_root="root=LABEL=ROOT"
+set linux_console=""
+
+# Anything else the OEM adds should use this variable.
+set linux_append=""
+
+
+# Search for the OEM partition, load additional configuration if found.
+search --no-floppy --set oem --label OEM --hint "$root"
+if [ -n "$oem" -a -f "($oem)/grub.cfg" ]; then
+    source "($oem)/grub.cfg"
+fi
+
+# If no specific console has been set by the OEM then select based on
+# platform, most systems use vga text as primary and ttyS0 as secondary.
+if [ -z "$linux_console" ]; then
+    if [ "$grub_platform" = pc ]; then
+        set linux_console="console=ttyS0,115200n8 console=tty0"
+        serial com0 --speed=115200 --word=8 --parity=no
+        terminal_input console serial_com0
+        terminal_output console serial_com0
+    elif [ "$grub_platform" = efi ]; then
+        set linux_console="console=ttyS0,115200n8 console=tty0"
+    elif [ "$grub_platform" = xen ]; then
+        set linux_console="console=hvc0"
+    fi
+fi
+
+
+# Load a kernel and boot! $root must point at USR-A or USR-B
+function load_coreos {
+    # UEFI uses linuxefi/initrdefi instead of linux/initrd
+    if [ "$grub_platform" = efi ]; then
+        set suf="efi"
+    else
+        set suf=""
+    fi
+
+    echo "Loading ($root)/boot/vmlinuz"
+    linux$suf /boot/vmlinuz $linux_console $linux_root "$@" $linux_append
+
+    if [ -f /boot/initrd ]; then
+        echo "Loading ($root)/boot/initrd"
+        initrd$suf /boot/initrd
+    fi
+
+    echo "Booting CoreOS!"
+}
+
+# TODO: systemd 217 added mount.usr=, once we update we should switch
+menuentry "CoreOS default" --id=coreos {
+    gptprio.next -d root -u usr_uuid
+    load_coreos usr=PARTUUID=$usr_uuid
+}
+
+menuentry "CoreOS USR-A" --id=coreos-a {
+    search --no-floppy --set root --part-label USR-A --hint "$root"
+    load_coreos usr=PARTLABEL=USR-A
+}
+
+menuentry "CoreOS USR-B" --id=coreos-b {
+    search --no-floppy --set root --part-label USR-B --hint "$root"
+    load_coreos usr=PARTLABEL=USR-B
+}
diff --git a/build_library/grub_install.sh b/build_library/grub_install.sh
index 59a6912323..8b69850023 100755
--- a/build_library/grub_install.sh
+++ b/build_library/grub_install.sh
@@ -29,11 +29,8 @@ switch_to_strict_mode
 # Our GRUB lives under coreos/grub so new pygrub versions cannot find grub.cfg
 GRUB_DIR="coreos/grub/${FLAGS_target}"
 
-# Assumes the ESP is the first partition, GRUB cannot search for it by type.
-GRUB_PREFIX="(,gpt1)/coreos/grub"
-
 # Modules required to find and read everything else from ESP
-CORE_MODULES=( fat part_gpt gzio )
+CORE_MODULES=( fat part_gpt search_fs_uuid gzio )
 
 # Name of the core image, depends on target
 CORE_NAME=
@@ -46,6 +43,9 @@ case "${FLAGS_target}" in
     x86_64-efi)
         CORE_NAME="core.efi"
         ;;
+    x86_64-xen)
+        CORE_NAME="core.elf"
+        ;;
     *)
         die_notrace "Unknown GRUB target ${FLAGS_target}"
         ;;
@@ -57,14 +57,10 @@ esac
 # the kernel can automatically detach the loop devices on unmount. When
 # using a single loop device with partitions there is no such cleanup.
 # That's the story of why this script has all this goo for loop and mount.
-STAGE_DIR=
 ESP_DIR=
 LOOP_DEV=
 
 cleanup() {
-    if [[ -d "${STAGE_DIR}" ]]; then
-        rm -rf "${STAGE_DIR}"
-    fi
     if [[ -d "${ESP_DIR}" ]]; then
         if mountpoint -q "${ESP_DIR}"; then
             sudo umount "${ESP_DIR}"
@@ -77,24 +73,7 @@ cleanup() {
 }
 trap cleanup EXIT
 
-STAGE_DIR=$(mktemp --directory)
-mkdir -p "${STAGE_DIR}/${GRUB_DIR}"
-
-info "Compressing modules in ${GRUB_DIR}"
-for file in "/usr/lib/grub/${FLAGS_target}"/*{.lst,.mod}; do
-    out="${STAGE_DIR}/${GRUB_DIR}/${file##*/}"
-    gzip --best --stdout "${file}" > "${out}"
-done
-
-info "Generating ${GRUB_DIR}/${CORE_NAME}"
-grub-mkimage \
-    --compression=auto \
-    --format "${FLAGS_target}" \
-    --prefix "${GRUB_PREFIX}" \
-    --output "${STAGE_DIR}/${GRUB_DIR}/${CORE_NAME}" \
-    "${CORE_MODULES[@]}"
-
-info "Installing GRUB ${FLAGS_target} to ${FLAGS_disk_image##*/}"
+info "Installing GRUB ${FLAGS_target} in ${FLAGS_disk_image##*/}"
 LOOP_DEV=$(sudo losetup --find --show --partscan "${FLAGS_disk_image}")
 ESP_DIR=$(mktemp --directory)
 
@@ -117,7 +96,33 @@ if [[ ! -b "${LOOP_DEV}p1" ]]; then
 fi
 
 sudo mount -t vfat "${LOOP_DEV}p1" "${ESP_DIR}"
-sudo cp -r "${STAGE_DIR}/." "${ESP_DIR}/."
+sudo mkdir -p "${ESP_DIR}/${GRUB_DIR}"
+
+info "Compressing modules in ${GRUB_DIR}"
+for file in "/usr/lib/grub/${FLAGS_target}"/*{.lst,.mod}; do
+    out="${ESP_DIR}/${GRUB_DIR}/${file##*/}"
+    gzip --best --stdout "${file}" | sudo_clobber "${out}"
+done
+
+info "Generating ${GRUB_DIR}/load.cfg"
+# Include a small initial config in the core image to search for the ESP
+# by filesystem ID in case the platform doesn't provide the boot disk.
+# The existing $root value is given as a hint so it is searched first.
+ESP_FSID=$(sudo grub-probe -t fs_uuid -d "${LOOP_DEV}p1")
+sudo_clobber "${ESP_DIR}/${GRUB_DIR}/load.cfg" <<EOF
+search.fs_uuid ${ESP_FSID} root \$root
+set prefix=(\$root)/coreos/grub
+set
+EOF
+
+info "Generating ${GRUB_DIR}/${CORE_NAME}"
+sudo grub-mkimage \
+    --compression=auto \
+    --format "${FLAGS_target}" \
+    --prefix "(,gpt1)/coreos/grub" \
+    --config "${ESP_DIR}/${GRUB_DIR}/load.cfg" \
+    --output "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
+    "${CORE_MODULES[@]}"
 
 # This script will get called a few times, no need to re-copy grub.cfg
 if [[ ! -f "${ESP_DIR}/coreos/grub/grub.cfg" ]]; then
@@ -136,9 +141,17 @@ case "${FLAGS_target}" in
     x86_64-efi)
         info "Installing default x86_64 UEFI bootloader."
         sudo mkdir -p "${ESP_DIR}/EFI/boot"
-        sudo cp "${STAGE_DIR}/${GRUB_DIR}/${CORE_NAME}" \
+        sudo cp "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
             "${ESP_DIR}/EFI/boot/bootx64.efi"
         ;;
+    x86_64-xen)
+        info "Installing default x86_64 Xen bootloader."
+        sudo mkdir -p "${ESP_DIR}/xen" "${ESP_DIR}/boot/grub"
+        sudo cp "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
+            "${ESP_DIR}/xen/pvboot-x86_64.elf"
+        sudo cp "${BUILD_LIBRARY_DIR}/menu.lst" \
+            "${ESP_DIR}/boot/grub/menu.lst"
+        ;;
 esac
 
 cleanup
diff --git a/build_library/menu.lst b/build_library/menu.lst
new file mode 100644
index 0000000000..05167b6abe
--- /dev/null
+++ b/build_library/menu.lst
@@ -0,0 +1,4 @@
+timeout 0
+title   CoreOS GRUB2
+root    (hd0,0)
+kernel  /xen/pvboot-x86_64.elf