当前在OpenStack中没有提供一个方便快捷的方法去创建镜像，需要运维人员使用KVM制作，这无疑提高了对运维人员和环境(需要一个安装了KVM的linux)的要求，因此我觉得OpenStack还是不适应于私有云的，它是为公有云而生。
本文介绍一种利用Horizon和ISO格式的安装盘来创建镜像的方法，其原理为：
1. 创建一个新的磁盘作为root disk
2. 从Glance下载ISO作为第二块磁盘
3. 从Glance下载virtio作为第三块磁盘
4. 从ISO启动虚拟机，比将系统安装到root disk
5. 创建image并保持到Glance
1.添加一种disk类型newos
- * 'mapping': a dict contains the storage device mapping.
- For the default disk types it will contain the following
- keys & values:
- 'disk' -> disk_info
- 'disk.rescue' -> disk_info
- 'disk.local' -> disk_info
- 'disk.swap' -> disk_info
- 'disk.config' -> disk_info
- 'disk.newos' -> disk_info
- disk_info指的是：
- * 'disk_info': a tuple specifying disk configuration
- It contains the following 3 fields
- (disk bus, disk dev, device type)
- * 'disk_bus': the guest bus type ('ide', 'virtio', 'scsi', etc)
- * 'disk_dev': the device name 'vda', 'hdc', 'sdf', 'xvde' etc
- * 'device_type': type of device eg 'disk', 'cdrom', 'floppy'
2 设置磁盘顺序
在blockinfo.py中，调用逻辑是：
spawn-->get_disk_info -->get_disk_mapping :
- if image_meta and image_meta.get('disk_format') == 'iso':
- root_disk_bus = disk_bus
- #创建虚拟机时如果image_meta中的disk_format为iso, 则认为是创建新image的操作，那么进行如下操作
- #设置disk.newos为root device
- root_device_type = 'disk'
- root_info = get_next_disk_info(mapping,
- root_disk_bus,
- root_device_type)
- mapping['root'] = root_info
- mapping['disk.newos'] = root_info
- #设置disk(iso)为第二个device
- image_device_type = 'cdrom'
- image_device_bus = cdrom_bus
- cdrom_info = get_next_disk_info(mapping,
- image_device_bus,
- image_device_type)
- mapping['disk'] = cdrom_info
- #s设置disk.virtio作为第三个设备，为需要virtio的时候提供virtio驱动程序
- virtio_device_type = 'cdrom'
- virtio_device_bus = cdrom_bus
- virtio_device_info = get_next_disk_info(mapping,
- virtio_device_bus,
- virtio_device_type)
- mapping['disk.virtio'] = virtio_device_info
- return mapping
#p#
3 创建磁盘
driver.py中的调逻辑是：spawn--> _create_image
- newos_size_gb = CONF.os_root_disk_size
- if 'disk.newos' in disk_mapping:
- fname = "newos_%s_%s" % (newos_size_gb, os_type_with_default)
- size = newos_size_gb * 1024 * 1024 * 1024
- image('disk.newos').cache(fetch_func=self._create_newos,
- filename=fname,
- size=size,
- newos_size=newos_size_gb)
- virtio_image_id = CONF.virtio_image_id
- virtio_images = {'image_id': virtio_image_id}
- virtio_fname = imagecache.get_cache_fname(virtio_images, 'image_id')
- image('disk.virtio').cache(fetch_func=libvirt_utils.fetch_image,
- context=context,
- filename=virtio_fname,
- size=size,
- image_id=virtio_image_id,
- user_id=instance['user_id'],
- project_id=instance['project_id'])
- @staticmethod
- def _create_newos(target, newos_size):
- #self._create_local(target, newos_size)
- unit='G'
- libvirt_utils.create_image('qcow2', target,
- '%d%c' % (newos_size, unit))
4. 将磁盘配置写入XML文件中
driver.py中的调逻辑是：spawn-->get_guest_xml--> get_guest_config-->_get_guest_storage_config
- if rescue:
- diskrescue = self.get_guest_disk_config(instance,
- 'disk.rescue',
- disk_mapping,
- inst_type)
- devices.append(diskrescue)
- diskos = self.get_guest_disk_config(instance,
- 'disk',
- disk_mapping,
- inst_type)
- devices.append(diskos)
- else:
- #添加device
- if 'disk.newos' in disk_mapping:
- disknewos = self.get_guest_disk_config(instance,
- 'disk.newos',
- disk_mapping,
- inst_type)
- devices.append(disknewos)
- diskcdrom = self.get_guest_disk_config(instance,
- 'disk',
- disk_mapping,
- inst_type)
- devices.append(diskcdrom)
- diskvirtio = self.get_guest_disk_config(instance,
- 'disk.virtio',
- disk_mapping,
- inst_type)
- devices.append(diskvirtio)
- ###
- else:
- if 'disk' in disk_mapping:
- diskos = self.get_guest_disk_config(instance,
- 'disk',
- disk_mapping,
- inst_type)
- devices.append(diskos)
参考：http://www.ibm.com/developerworks/cn/cloud/library/cl-openstack-images/
