Merge lp:~yuningdodo/usb-creator/usb-creator.lp1325801v4-exec-syslinux-in-chroot into lp:usb-creator

[Yu Ning]

[Yu Ning (yuningdodo)]

Some test results can be found here:
https://bugs.launchpad.net/ubuntu/+source/usb-creator/+bug/1325801/comments/138

[lp:~yuningdodo/usb-creator/usb-creator.lp1325801v4-exec-syslinux-in-chroot]

473. By Yu Ning on 2015-05-08

* attempt overlay methods with a loop.

Unmerged revisions

473. By Yu Ning on 2015-05-08

* attempt overlay methods with a loop.

472. By Yu Ning on 2015-05-06

* Install syslinux in a chroot environment so we can also burn an i386 ISO on an amd64 host. (LP: #1325801)

=== modified file 'bin/usb-creator-helper'
--- bin/usb-creator-helper	2015-04-23 15:19:07 +0000
+++ bin/usb-creator-helper	2015-05-08 05:58:21 +0000
@@ -191,41 +191,68 @@
             popen(['dd', 'if=%s' % os.path.join(grub_location, 'core.img'), 'of=%s' % parent_file,
                    'bs=512', 'count=62', 'seek=1', 'conv=sync'])
         else:
-            if syslinux_legacy and find_on_path('syslinux-legacy'):
-                syslinux_var = "syslinux-legacy"
-                syslinux_exe = "syslinux-legacy"
-                syslinux_bin = "/usr/lib/syslinux-legacy/mbr.bin"
-            else:
-                syslinux_var = "syslinux"
-                syslinux_exe = "syslinux"
-                syslinux_bin = "/usr/lib/syslinux/mbr/mbr.bin"
-                if not os.path.exists(syslinux_bin):
-                    syslinux_bin = "/usr/lib/syslinux/mbr.bin"
             squashfs_mnt = ''
             target_mounts = obj.get_filesystem().get_cached_property('MountPoints').get_bytestring_array()
             if len(target_mounts) > 0:
                 target_mnt = target_mounts[0]
-                squashfs_img = os.path.join(target_mnt, 'casper',
-                                            'filesystem.squashfs')
-                if os.path.exists(squashfs_img):
-                    # Mount the squashfs so we are possible to install
-                    # syslinux & mbr.bin from it.
-                    squashfs_mnt = self.MountISO(squashfs_img)
-            if squashfs_mnt:
-                for mbrbin in [
-                        os.path.join(squashfs_mnt, 'usr', 'lib',
-                                     syslinux_var, 'mbr.bin'),
-                        os.path.join(squashfs_mnt, 'usr', 'lib',
-                                     syslinux_var, 'mbr', 'mbr.bin'),
-                        os.path.join(squashfs_mnt, 'usr', 'lib',
-                                     syslinux_var.upper(), 'mbr.bin'),
-                        ]:
-                    if os.path.exists(mbrbin):
-                        syslinux_exe = os.path.join(squashfs_mnt, 'usr',
-                                                    'bin', syslinux_var)
-                        syslinux_bin = mbrbin
-                        break
-            popen([syslinux_exe, '-f', device])
+                for place in [ 'install', 'casper', 'live' ]:
+                    squashfs_img = os.path.join(target_mnt, place,
+                                                'filesystem.squashfs')
+                    if os.path.exists(squashfs_img):
+                        # Mount the squashfs so we are possible to install
+                        # syslinux & mbr.bin from it.
+                        squashfs_mnt = self.MountISO(squashfs_img)
+                        break
+            syslinux_exe = ''
+            syslinux_bin = ''
+            for prefix in [ squashfs_mnt, os.path.sep ]:
+                if not prefix:
+                    continue
+                for syslinux_var in [ 'syslinux-legacy', 'syslinux' ]:
+                    if syslinux_var == 'syslinux-legacy' and not syslinux_legacy:
+                        continue
+                    syslinux_exe = os.path.join(os.path.sep,
+                                                'usr', 'bin', syslinux_var)
+                    if not os.path.exists(os.path.join(prefix, syslinux_exe)):
+                        continue
+                    for mbrbin in [
+                            os.path.join(prefix, 'usr', 'lib',
+                                         syslinux_var, 'mbr.bin'),
+                            os.path.join(prefix, 'usr', 'lib',
+                                         syslinux_var, 'mbr', 'mbr.bin'),
+                            os.path.join(prefix, 'usr', 'lib',
+                                         syslinux_var.upper(), 'mbr.bin'),
+                            ]:
+                        if os.path.exists(mbrbin):
+                            syslinux_bin = mbrbin
+                            break
+                    if syslinux_bin:
+                        break
+                if syslinux_bin:
+                    if squashfs_mnt and prefix == squashfs_mnt:
+                        overlay = self.mount_overlay(squashfs_mnt)
+                        if not overlay:
+                            continue
+                        popen(['mount', '-n', '-o', 'bind', '/proc/',
+                               os.path.join(overlay, 'proc')])
+                        popen(['mount', '-n', '-o', 'bind', '/dev/',
+                               os.path.join(overlay, 'dev')])
+                        try:
+                            popen(['chroot', overlay,
+                                   syslinux_exe, '-f', device])
+                        except:
+                            syslinux_bin = ''
+                            continue
+                        finally:
+                            popen(['umount', os.path.join(overlay, 'dev')])
+                            popen(['umount', os.path.join(overlay, 'proc')])
+                            self.UnmountFile(overlay)
+                    else:
+                        popen([syslinux_exe, '-f', device])
+                    break
+            if not syslinux_bin:
+                # syslinux not found
+                raise dbus.DBusException('com.ubuntu.USBCreator.Error.SystemInternal')
             # Write the syslinux MBR.
             popen(['dd', 'if=%s' % syslinux_bin, 'of=%s' % parent_file,
                    'bs=446', 'count=1', 'conv=sync'])
@@ -345,6 +372,28 @@
         logging.debug('Shutting down.')
         loop.quit()
 
+    def mount_overlay(self, directory):
+        import tempfile
+        ret = tempfile.mkdtemp()
+        delta = tempfile.mkdtemp()
+        work = tempfile.mkdtemp()
+        methods = [
+            [ 'mount', '-t', 'overlay', 'overlay', '-o',
+              'lowerdir=%s,upperdir=%s,workdir=%s' % (directory, delta, work),
+              ret ],
+            [ 'mount', '-t', 'aufs', 'none', '-o',
+              'br=%s:%s' % (delta, directory), ret ],
+            [ 'mount', '-t', 'overlayfs', 'overlayfs', '-o',
+              'lowerdir=%s,upperdir=%s' % (directory, delta), ret ],
+        ]
+        for method in methods:
+            try:
+                popen(method)
+                return ret
+            except:
+                pass
+        return None
+
     # Taken from Jockey 0.5.3.
     def check_polkit(self, sender, conn, priv):
         if sender is None and conn is None: