Add more choices to grub2 menu.

src/scripts/build_image

 #!/bin/bash
 
 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to build a bootable keyfob-based chromeos system image from within
 # a chromiumos setup. This assumes that all needed packages have been built into
 # the given target's root with binary packages turned on. This script will
 # build the Chrome OS image using only pre-built binary packages.
@@ skipping 364 matching lines @@
 sudo losetup "${ESP_LOOP_DEV}" "${ESP_IMG}"
 sudo mount "${ESP_LOOP_DEV}" "${ESP_DIR}"
 sudo mkdir -p "${ESP_DIR}/efi/boot"
 sudo grub-mkimage -p /efi/boot -o "${ESP_DIR}/efi/boot/bootx64.efi" \
   part_gpt fat ext2 normal boot sh chain configfile linux
 sudo cp "${ROOT_FS_DIR}/boot/vmlinuz" "${ESP_DIR}/efi/boot/vmlinuz"
 cat <<EOF | sudo dd of="${ESP_DIR}/efi/boot/grub.cfg"
 set timeout=2
 set default=0
 
-menuentry "normal" {
+menuentry "boot from disk" {
   linux /efi/boot/vmlinuz quiet console=tty2 init=/sbin/init boot=local rootwait root=/dev/sda3 ro noresume noswap i915.modeset=1 loglevel=1
 }
 
-menuentry "serial debug" {
+menuentry "boot from disk with serial debug" {
   linux /efi/boot/vmlinuz earlyprintk=serial,ttyS0,115200 console=ttyS0,115200 init=/sbin/init boot=local rootwait root=/dev/sda3 ro noresume noswap i915.modeset=1 loglevel=7
 }
 
+menuentry "boot from usb" {
+  linux /efi/boot/vmlinuz quiet console=tty2 init=/sbin/init boot=local rootwait root=/dev/sdb3 ro noresume noswap i915.modeset=1 loglevel=1
+}
+
+menuentry "boot from usb with serial debug" {
+  linux /efi/boot/vmlinuz earlyprintk=serial,ttyS0,115200 console=ttyS0,115200 init=/sbin/init boot=local rootwait root=/dev/sdb3 ro noresume noswap i915.modeset=1 loglevel=7
+}
+
 EOF
 
 # Run ldconfig for rootfs's ld.so.cache
 if [ $FLAGS_statefuldev -eq $FLAGS_TRUE ] ; then
   # Re-run ldconfig to fix /etc/ldconfig.so.cache
   sudo /sbin/ldconfig -r "$ROOT_FS_DIR"
 
   #TODO(sosa@chromium.org) - /usr/bin/xterm symlink not created in stateful.
   sudo ln -sf "/usr/local/bin/aterm" "/usr/bin/xterm"
 fi
@@ skipping 28 matching lines @@
 
 OUTSIDE_OUTPUT_DIR="../build/images/${FLAGS_board}/${IMAGE_SUBDIR}"
 echo "Done.  Image created in ${OUTPUT_DIR}"
 echo "To copy to USB keyfob, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_usb.sh --from=${OUTSIDE_OUTPUT_DIR} --to=/dev/sdX"
 echo "To convert to VMWare image, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_vmware.sh --from=${OUTSIDE_OUTPUT_DIR}"
 echo "from the scripts directory where you entered the chroot."
 
 trap - EXIT