Extlinux fallback

If GRUB2 is not available in the system a fallback to install Extlinux
will happen. This patch also allows you to enforce the use of Extlinux
exporting the DIB_EXTLINUX variable.

Change-Id: I88fa792a0bd19cacca167134f2054b11c807a451

elements/fedora/bin/map-packages

@@ -49,6 +49,7 @@ package_map = {
     'openssh-client': 'openssh-clients',
     'qpidd': 'qpid-cpp-server',
     'qpid-client': 'qpid-cpp-client',
+    'extlinux': 'syslinux-extlinux',
     }
 
 for arg in sys.argv[1:]:

elements/vm/README.md

@@ -1,5 +1,7 @@
 Sets up a partitioned disk (rather than building just one filesystem with no
 partition table).
 
-The disk will have grub[2]-install run on it, and that assumes a functional
-grub[2] setup.
+By default the disk will have grub[2]-install run on it, in case GRUB2
+is not available in the system a fallback to Extlinux will happen. It's
+also possible to enforce the use of Extlinux exporting a DIB_EXTLINUX
+varible to the environment.

elements/vm/finalise.d/51-bootloader

@@ -6,6 +6,53 @@
 set -e
 set -x
 
+# FIXME:
+[ -n "$IMAGE_BLOCK_DEVICE" ]
+PART_DEV=$IMAGE_BLOCK_DEVICE
+BOOT_DEV=$(echo $IMAGE_BLOCK_DEVICE | sed -e 's#p1##' | sed -e 's#mapper/##')
+
+function install_extlinux {
+    install-packages extlinux
+
+    echo "Installing Extlinux..."
+
+    MBR=/usr/share/syslinux/mbr.bin
+    if [ ! -f $MBR ]; then
+        MBR=/usr/lib/syslinux/mbr.bin
+        if [ ! -f $MBR ]; then
+            echo "mbr.bin (from SYSLINUX) not found."
+            exit 1
+        fi
+    fi
+
+    dd if=$MBR of=$BOOT_DEV
+
+    mkdir -p /boot/syslinux
+    extlinux --install /boot/syslinux
+
+    if [ -f /etc/redhat-release ]; then
+        kernel=$(ls -1rv /boot/vmlinuz* | head -1)
+        initrd=$(ls -1rv /boot/initramfs* | head -1)
+    elif [ -f /etc/debian_version ]; then
+        kernel=$(ls -1rv /boot/vmlinuz*generic | head -1)
+        initrd=$(ls -1rv /boot/initrd*generic | head -1)
+    else
+        echo "Unable to find kernel and initram"
+        exit 1
+    fi
+
+    cat > /boot/syslinux/syslinux.cfg<<_EOF_
+DEFAULT linux
+
+LABEL linux
+  KERNEL $kernel
+  APPEND rw root=LABEL=cloudimg-rootfs
+  INITRD  $initrd
+_EOF_
+}
+
+function install_grub2 {
+
     install-packages grub-pc
 
     # XXX: grub-probe on the nbd0/loop0 device returns nothing - workaround, manually
@@ -14,14 +61,16 @@ GRUBNAME=`which grub-install` || echo "trying grub2-install"
     if [ -z "$GRUBNAME" ]; then
         GRUBNAME="bash -x `which grub2-install`"
     fi
-if [ -z "$GRUBNAME" ]; then
-    echo "NO grub-install or grub2-install found"
-    exit 1
+
+    # If no GRUB2 is found, fallback to extlinux
+    if [ -z "$GRUBNAME" ] || [ $($GRUBNAME --version | grep "0.97" | wc -l) -ne 0 ]; then
+        echo "No GRUB2 found. Fallback to Extlinux..."
+        install_extlinux
+        exit 0
     fi
-# FIXME:
-[ -n "$IMAGE_BLOCK_DEVICE" ]
-PART_DEV=$IMAGE_BLOCK_DEVICE
-BOOT_DEV=$(echo $IMAGE_BLOCK_DEVICE | sed -e 's/p1//')
+
+    echo "Installing GRUB2..."
+
     GRUB_OPTS=${GRUB_OPTS:""}
     # XXX: This is buggy:
     # - --target=i386-pc is invalid for non-i386/amd64 architectures
@@ -104,3 +153,11 @@ if [ $DIST = 'Fedora' ] ; then
         sed -i "s%UUID=[A-Za-z0-9\-]*%LABEL=cloudimg-rootfs%" /etc/fstab
       fi
     fi
+}
+
+DIB_EXTLINUX=${DIB_EXTLINUX:-0}
+if [ "$DIB_EXTLINUX" != "0" ]; then
+    install_extlinux
+else
+    install_grub2
+fi