Example config_drive init script, label the config drive

Configuration with DHCP & cloud-init can be painful.  The config_drive is great,
and it avoids disk injection, but there's no example of how to use it.

So here's a little example init.d script for contrib, and a code patch to make
sure the config drive gets a nice volume label.

Change-Id: I22a1d6a824856ca9651b435d0fe54e348ab107fe

2 files changed, 12 insertions, 5 deletions

diff --git a/nova/virt/libvirt/connection.py b/nova/virt/libvirt/connection.py
index fe2df8012..556607666 100644
--- a/nova/virt/libvirt/connection.py
+++ b/nova/virt/libvirt/connection.py
@@ -954,7 +954,8 @@ class LibvirtConnection(driver.ComputeDriver):
                     disk.extend(target, size)
 
     @staticmethod
-    def _create_local(target, local_size, unit='G', fs_format=None):
+    def _create_local(target, local_size, unit='G',
+                      fs_format=None, label=None):
         """Create a blank image of specified size"""
 
         if not fs_format:
@@ -963,7 +964,7 @@ class LibvirtConnection(driver.ComputeDriver):
         libvirt_utils.create_image('raw', target,
                                    '%d%c' % (local_size, unit))
         if fs_format:
-            libvirt_utils.mkfs(fs_format, target)
+            libvirt_utils.mkfs(fs_format, target, label)
 
     def _create_ephemeral(self, target, ephemeral_size, fs_label, os_type):
         self._create_local(target, ephemeral_size)
@@ -1109,8 +1110,9 @@ class LibvirtConnection(driver.ComputeDriver):
                               user_id=instance['user_id'],
                               project_id=instance['project_id'],)
         elif config_drive:
+            label = 'config'
             self._create_local(basepath('disk.config'), 64, unit='M',
-                               fs_format='msdos')  # 64MB
+                               fs_format='msdos', label=label)  # 64MB
 
         if instance['key_data']:
             key = str(instance['key_data'])
diff --git a/nova/virt/libvirt/utils.py b/nova/virt/libvirt/utils.py
index da3f95d4f..329f76eb1 100644
--- a/nova/virt/libvirt/utils.py
+++ b/nova/virt/libvirt/utils.py
@@ -118,17 +118,22 @@ def copy_image(src, dest):
     execute('cp', src, dest)
 
 
-def mkfs(fs, path):
+def mkfs(fs, path, label=None):
     """Format a file or block device
 
     :param fs: Filesystem type (examples include 'swap', 'ext3', 'ext4'
                'btrfs', etc.)
     :param path: Path to file or block device to format
+    :param label: Volume label to use
     """
     if fs == 'swap':
         execute('mkswap', path)
     else:
-        execute('mkfs', '-t', fs, path)
+        args = ['mkfs', '-t', fs]
+        if label:
+            args.extend(['-n', label])
+        args.append(path)
+        execute(*args)
 
 
 def ensure_tree(path):