configure_bootloaders: add grub install stub code

Not currently used, this configuration which sets up grub to re-use the
syslinux configuration only works with recent git versions, not any
releases. Compatibility is also limited because the serial configuration
in syslinux must be duplicated in the grub config.

build_library/configure_bootloaders.sh

@@ -51,7 +51,7 @@ GRUB_DIR="${FLAGS_boot_dir}/grub"
 SYSLINUX_DIR="${FLAGS_boot_dir}/syslinux"
 
 # Build configuration files for pygrub/pvgrub
-configure_grub() {
+configure_pvgrub() {
   sudo mkdir -p "${GRUB_DIR}"
 
   # Add hvc0 for hypervisors
@@ -177,12 +177,28 @@ copy_to_esp() {
   done
 }
 
+# Install GRUB2 to the disk image
+install_grub() {
+  # Install under boot/coreos/grub instead of boot/grub to prevent
+  # more recent versions of pygrub that attempt to read grub2 configs
+  # from finding it, pygrub and pvgrub must stick with using menu.lst
+  sudo mkdir -p "${FLAGS_esp_dir}/coreos/grub"
+  sudo grub-install \
+      --target=i386-pc \
+      --modules=part_gpt \
+      --boot-directory="${FLAGS_esp_dir}/coreos" \
+      "${FLAGS_disk_image}"
+  sudo cp "${BUILD_LIBRARY_DIR}/grub.cfg" \
+      "${FLAGS_esp_dir}/coreos/grub/grub.cfg"
+}
+
+[[ -d "${FLAGS_esp_dir}" ]] || die_notrace "--esp_dir is required"
+[[ -f "${FLAGS_disk_image}" ]] || die_notrace "--disk_image is required"
+
 if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64"  ]]; then
-  configure_grub
+  configure_pvgrub
   configure_syslinux
-  if [[ -n "${FLAGS_esp_dir}" ]]; then
-    copy_to_esp
-  fi
+  copy_to_esp
 else
   error "No bootloader configuration for ${FLAGS_arch}"
 fi

build_library/grub.cfg

@@ -0,0 +1,9 @@
+# Use both default console and ttyS0
+serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
+terminal_input console serial
+terminal_output console serial
+
+# Re-use the existing syslinux configuration
+echo "Loading SYSLINUX configuration..."
+insmod syslinuxcfg
+syslinux_configfile -s /syslinux/syslinux.cfg