Reinstall extlinux after shrinking if needed

If extlinux is installed on the root partition (the OS does not have a
separate /boot partition) it needs to be reinstalled, otherwise the OS
won't boot.

image_creator/image.py

@@ -299,8 +299,8 @@ class Image(object):
         """Shrink the image.
 
         This is accomplished by shrinking the last file system of the
-        image and then updating the partition table. The new disk size
-        (in bytes) is returned.
+        image and then updating the partition table. The shrinked device is
+        returned.
 
         ATTENTION: make sure umount is called before shrink
         """
@@ -351,7 +351,7 @@ class Image(object):
         if self.is_unsupported():
             if not silent:
                 self.out.warn("Shrinking is disabled for unsupported images")
-            return self.size
+            return None
 
         sector_size = self.g.blockdev_getss(self.guestfs_device)
 
@@ -381,7 +381,7 @@ class Image(object):
             if not silent:
                 self.out.warn(
                     "Don't know how to shrink %s partitions." % fstype)
-            return self.size
+            return None
 
         part_dev = "%s%d" % (self.guestfs_device, last_part['part_num'])
 
@@ -461,7 +461,7 @@ class Image(object):
             self.out.success("Image size is %dMB" %
                              ((self.size + MB - 1) // MB))
 
-        return self.size
+        return part_dev
 
     def mount(self, mpoint, readonly=False):
         """Mount the image file system under a local directory"""

image_creator/os_type/__init__.py

@@ -20,7 +20,7 @@ Systems for image creation.
 """
 
 from image_creator.util import FatalError
-from image_creator.bootloader import mbr_bootinfo
+from image_creator.bootloader import mbr_bootinfo, vbr_bootinfo
 
 import textwrap
 import re
@@ -483,9 +483,28 @@ class OSBase(object):
     @sysprep('Shrinking image (may take a while)', nomount=True)
     def _shrink(self):
         """Shrink the last file system and update the partition table"""
-        self.image.shrink()
+        device = self.image.shrink()
         self.shrinked = True
 
+        # Check the Volume Boot Record of the shrinked partition to determine
+        # if a bootloader is present on it.
+        vbr = self.image.g.pread_device(device, 512, 0)
+        bootloader = vbr_bootinfo(vbr)
+
+        if bootloader == 'syslinux':
+            # EXTLINUX needs to be reinstalled after shrinking
+            with self.mount(silent=True):
+                self.out.info("Reinstalling extlinux ...", False)
+                if self.image.g.is_dir('/boot/extlinux'):
+                    extdir = '/boot/extlinux'
+                elif self.image.g.is_dir('/boot/syslinux'):
+                    extdir = '/boot/syslinux'
+                else:
+                    extdir = '/boot'
+
+                self.image.g.command(['extlinux', '--install', extdir])
+                self.out.success("done")
+
     @property
     def ismounted(self):
         return self._mounted is not None