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

contrib/openstack-config

@@ -0,0 +1,65 @@
+#!/bin/sh -e
+### BEGIN INIT INFO
+# Provides:          openstack
+# Required-Start:    mountkernfs $local_fs
+# Required-Stop:     $local_fs
+# X-Start-Before:    networking
+# Should-Start:
+# Default-Start:     S
+# Default-Stop:
+# Short-Description: Apply configuration from OpenStack Config Drive
+### END INIT INFO
+
+PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
+
+. /lib/lsb/init-functions
+
+copy_cloud_config() {
+  LABEL="config"
+  if [ ! -e /dev/disk/by-label/${LABEL} ]; then
+    log_warning_msg "OpenStack Cloud Config drive not found"
+    return 1
+  fi
+
+  MNT=/tmp/config
+  mkdir -p ${MNT}
+  mount /dev/disk/by-label/${LABEL} ${MNT}
+  if [ -e ${MNT}/root/.ssh/authorized_keys ]; then
+    mkdir -m 700 -p /root/.ssh/
+    cp ${MNT}/root/.ssh/authorized_keys /root/.ssh/
+    chmod 600 ${MNT}/root/.ssh/authorized_keys
+  fi
+  if [ -e ${MNT}/etc/network/interfaces ]; then
+    cp ${MNT}/etc/network/interfaces /etc/network/
+    chmod 644 /etc/network/interfaces
+  fi
+  umount ${MNT}
+  return 0
+}
+
+case "$1" in
+  start|"")
+    log_action_begin_msg "Applying OpenStack Cloud Config"
+    if copy_cloud_config; then
+      log_action_end_msg $?
+    else
+      log_action_end_msg $?
+    fi
+  ;;
+
+  restart|reload|force-reload|status)
+    echo "Error: argument '$1' not supported" >&2
+    exit 3
+  ;;
+
+  stop)
+    # No-op
+  ;;
+
+  *)
+    echo "Usage: openstack.sh [start|stop]" >&2
+    exit 3
+  ;;
+esac
+
+:

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'])

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):