raw.py: create device nodes to access own disk

This patch creates loop-back devices in /dev of the image so that it would be
possible to access own disk from within chroot environment. This makes it
possible to install extlinux from chroot, not outside of chroot, as it is done
now. This also allows to do extlinux installation in an installer framework
plugin.

I do realize that this is not the most beautiful thing to do, but it works - I
have a script which installs extlinux when I run it from %post.

Change-Id: I2b14962a37524a15c5dc493572ae8e91ca8523ae
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@intel.com>

diff --git a/mic/imager/raw.py b/mic/imager/raw.py
index 81f0daa..e00db84 100644 (file)
--- a/mic/imager/raw.py
+++ b/mic/imager/raw.py
@@ -218,6 +218,69 @@ class RawImageCreator(BaseImageCreator):
         self.__instloop.mount()
         self._create_mkinitrd_config()
 
+    def mount(self, base_on = None, cachedir = None):
+        """
+        This method calls the base class' 'mount()' method and then creates
+        block device nodes corresponding to the image's partitions in the image
+        itself. Namely, the image has /dev/loopX device corresponding to the
+        entire image, and per-partition /dev/mapper/* devices.
+
+        We copy these files to image's "/dev" directory in order to enable
+        scripts which run in the image chroot environment to access own raw
+        partitions. For example, this can be used to install the bootloader to
+        the MBR (say, from an installer framework plugin).
+        """
+
+        def copy_devnode(src, dest):
+            """A helper function for copying device nodes."""
+
+            stat_obj = os.stat(src)
+            assert stat.S_ISBLK(stat_obj.st_mode)
+
+            os.mknod(dest, stat_obj.st_mode,
+                     os.makedev(os.major(stat_obj.st_rdev),
+                                os.minor(stat_obj.st_rdev)))
+            # os.mknod uses process umask may create a nod with different
+            # permissions, so we use os.chmod to make sure permissions are
+            # correct.
+            os.chmod(dest, stat_obj.st_mode)
+
+        BaseImageCreator.mount(self, base_on, cachedir)
+
+        # Copy the disk loop devices
+        for name in self.__disks.keys():
+            loopdev = self.__disks[name].device
+            copy_devnode(loopdev, self._instroot + loopdev)
+
+        # Copy per-partition dm nodes
+        os.mkdir(self._instroot + "/dev/mapper", os.stat("/dev/mapper").st_mode)
+        for p in self.__instloop.partitions:
+            copy_devnode(p['mapper_device'],
+                         self._instroot + p['mapper_device'])
+
+    def unmount(self):
+        """
+        Remove loop/dm device nodes which we created in 'mount()' and call the
+        base class' 'unmount()' method.
+        """
+
+        for p in self.__instloop.partitions:
+            path = self._instroot + p['mapper_device']
+            if os.path.exists(path):
+                os.unlink(path)
+
+        path = self._instroot + "/dev/mapper"
+        if os.path.exists(path):
+            os.rmdir(path)
+
+        for name in self.__disks.keys():
+            if self.__disks[name].device:
+                path = self._instroot + self.__disks[name].device
+                if os.path.exists(path):
+                    os.unlink(path)
+
+        BaseImageCreator.unmount(self)
+
     def _get_required_packages(self):
         required_packages = BaseImageCreator._get_required_packages(self)
         if self._need_extlinux: