Install GRUB once, at most (second take, issue #78)

diff --git a/grml-debootstrap b/grml-debootstrap
index f218f7c..622a693 100755 (executable)
--- a/grml-debootstrap
+++ b/grml-debootstrap
@@ -1093,12 +1093,15 @@ finalize_vm() {
     bailout 1
   fi
 
-  einfo "Installing Grub as bootloader."
   mount -t proc none "${MNTPOINT}"/proc
   mount -t sysfs none "${MNTPOINT}"/sys
   mount --bind /dev "${MNTPOINT}"/dev
   mount --bind /dev/pts "${MNTPOINT}"/dev/pts
 
+# Has chroot-script installed GRUB to MBR using grub-install (successfully), already?
+# chroot-script skips installation for unset ${GRUB}
+if [[ -z "${GRUB}" ]] || ! dd if="${GRUB}" bs=512 count=1 2>/dev/null | cat -v | fgrep -q GRUB; then
+  einfo "Installing Grub as bootloader."
   mkdir -p "${MNTPOINT}/boot/grub"
   if ! [ -d "${MNTPOINT}"/usr/lib/grub/i386-pc/ ] ; then
      eerror "Error: grub not installed inside Virtual Machine. Can not install bootloader." ; eend 1
@@ -1116,6 +1119,7 @@ finalize_vm() {
   chroot "${MNTPOINT}" grub-mkimage -O i386-pc -p "(hd0,msdos1)/boot/grub" -o /tmp/core.img biosdisk part_msdos ext2
   dd if="${MNTPOINT}/tmp/core.img" of="${ORIG_TARGET}" conv=notrunc seek=4
   rm -f "${MNTPOINT}/tmp/core.img"
+fi
 
   einfo "Updating grub configuration file."
   if [ -n "$BOOT_APPEND" ] ; then