Xen 到 KVM 的迁移指南 #

本章包含可帮助您将虚拟机从外部超级管理程序（例如 Xen）导入到 libvirt 所管理的 KVM 的信息。

提示：Microsoft Windows Guest

本章重点介绍如何转换 Linux Guest。使用 virt-v2v 转换 Microsoft Windows Guest 与转换 Linux Guest 的过程相同，只不过对虚拟机驱动程序包 (VMDP) 的处理有所不同。虚拟机驱动程序包文档 中提供了有关转换使用 VMDP 的 Windows Guest 的更多细节。

tux > sudo zypper install virt-v2v

1.3 准备虚拟机 #

 

注意：跳过此步骤的条件

如果在 SLES 12 SP1 或之前的版本上运行 virt-v2v，可以放心跳过此步骤。如果虚拟机已完全虚拟化或者在 SLES 12 SP2 或更高版本上运行，也可以忽略此步骤。

Xen 虚拟机必须安装默认内核。要确保已执行此操作，请在虚拟机上运行 zypper in kernel-default。

1.4 将虚拟机转换为在 libvirt 管理的 KVM 下运行 #

 

virt-v2v 可将 Xen 超级管理程序中的虚拟机转换为在 libvirt 管理的 KVM 下运行。要了解有关 libvirt 和 virsh 的详细信息，请参见第 II 部分 “使用 libvirt 管理虚拟机”。此外，virt-v2v 手册页 (man 1 virt-v2v) 中也对所有 virt-v2v 命令行选项进行了说明。

转换虚拟机之前，请务必完成以下步骤：

过程 1︰ 准备转换环境 #

 

1. 创建新的本地储存池。

   virt-v2v 会将源虚拟机的储存复制到 libvirt 所管理的本地储存池（原始磁盘映像保持不变）。您可以使用虚拟机管理器或 virsh 创建该池。有关详细信息，请参见第 12.1 节 “使用虚拟机管理器管理储存”和第 12.2 节 “使用 virsh 管理储存”。

2. 准备本地网络接口。

   检查转换的虚拟机能否使用 VM 主机服务器上的本地网络接口。该接口通常是一个网桥。如果尚未定义接口，请单击 YaST › 系统 › 网络设置 › 添加 › 网桥创建。

   

   注意：网络设备的映射

   在转换过程中，可能会将源 Xen 主机上的网络设备映射到 KVM 目标主机上的相应网络设备。例如，可能会将 Xen 网桥 br0 映射到 KVM 网络 default。/etc/virt-v2v.conf 中提供了一些示例映射。要启用这些映射，请根据需要修改 XML 规则，并确保未以 <! -- 和 --> 标记注释相应部分。例如：

    <network type='bridge' name='br0'>
      <network type='network' name='default'/>
    </network>

   

   提示：无网桥

   如果没有可用的网桥，虚拟机管理器可以选择性创建一个。

virt-v2v 的基本命令语法如下：

virt-v2v -i INPUT_METHOD -os STORAGE_POOL SOURCE_VM

input_method

输入方法有以下两种：libvirt 或 libvirtxml。有关详细信息，请参见 SOURCE_VM 参数。

storage_pool

您已为目标虚拟机准备好的储存池。

source_vm

要转换的源虚拟机。其值取决于 INPUT_METHOD 参数：如果输入方法为 libvirt，需指定 libvirt 域的名称。如果输入方法为 libvirtxml，需指定包含 libvirt 域规范的 XML 文件的路径。

注意：转换时间

转换虚拟机时会占用大量系统资源，主要用于复制虚拟机的整个磁盘映像。转换单个虚拟机一般最多需要 10 分钟时间，但如果虚拟机使用的磁盘映像非常大，转换时间可能会长很多。

1.4.1 基于 libvirt XML 描述文件的转换 #

 

本节说明如何使用 libvirt XML 配置文件转换本地 Xen 虚拟机。如果主机已在运行 KVM 超级管理程序，则适合使用此方法。确保在本地主机上可以使用源虚拟机的 libvirt XML 文件以及其中引用的 libvirt 储存池。

1. 获取源虚拟机的 libvirt XML 描述。

   

   提示：获取 XML 文件

   要获取源虚拟机的 libvirt XML 文件，您必须在 Xen 内核下运行主机操作系统。如果您已将主机重引导至启用了 KVM 的环境，请将其重引导回 Xen 内核，转储 libvirt XML 文件，然后再重引导回 KVM 环境。

   首先，识别 virsh 下的源虚拟机：

   root # virsh list
    Id    Name                           State
   ----------------------------------------------------
   [...]
     2     sles12_xen                     running
   [...]

   sles12_xen 是要转换的源虚拟机。现在，导出其 XML 并保存到 sles12_xen.xml：

   root # virsh dumpxml sles12_xen > sles12_xen.xml

2. 从 KVM 主机的角度校验所有磁盘映像路径是否正确。在一台计算机上转换时，路径正确与否不会产生问题，但使用 XML 转储从其他主机进行转换时，可能需要手动更改路径。

   <source file='/var/lib/libvirt/images/XenPool/SLES.qcow2'/>

   

   提示：复制映像

   为避免将映像复制两次，请直接手动将磁盘映像复制到 libvirt 储存池。更新 XML 描述文件中的源文件项。virt-v2v 进程将检测到现有磁盘，并就地转换这些磁盘。

3. 运行 virt-v2v 以转换为 KVM 虚拟机：

   root # virt-v2v sles12_xen.xml1 \
   -i LIBVIRTXML2 \
   -os remote_host.example.com:/exported_dir3 \
   --bridge br04 \
   -on sles12_kvm5

   1	基于 Xen 的源虚拟机的 XML 描述。
   2	virt-v2v 将从 libvirt XML 文件中读取有关源虚拟机的信息。
   3	将放置目标虚拟机磁盘映像的储存池。在此示例中，映像将放置在 remote_host.example.com 服务器的 NFS 共享 /exported_dir 上。
   4	基于 KVM 的目标虚拟机将使用主机上的网桥 br0。
   5	目标虚拟机将重命名为 sles12_kvm，以防与同名的现有虚拟机发生名称冲突。

1.4.2 基于 libvirt 域名的转换 #

 

如果您仍在 Xen 下运行 libvirt，打算稍后重引导到 KVM 超级管理程序，则此方法很有用。

1. 确定您要转换的虚拟机的 libvirt 域名。

   root # virsh list
    Id    Name                           State
   ----------------------------------------------------
   [...]
     2     sles12_xen                     running
   [...]

   sles12_xen 是要转换的源虚拟机。

2. 运行 virt-v2v 以转换为 KVM 虚拟机：

   root # virt-v2v sles12_xen1 \
   -i libvirt2 \
   -os storage_pool3 \
   --network eth04 \
   -of qcow25 \
   -oa sparce6 \
   -on sles12_kvm

   1	基于 Xen 的虚拟机的域名。
   2	virt-v2v 将直接通过活动的 libvirt 连接读取有关源虚拟机的信息。
   3	目标磁盘映像将放置在本地 libvirt 储存池中。
   4	所有 Guest 网桥（或网络）都将连接到本地管理的网络。
   5	目标虚拟机的磁盘映像的格式。支持的选项为 raw 或 qcow2。
   6	转换的 Guest 磁盘空间将采用稀疏模式还是预分配模式。

1.4.3 转换远程 Xen 虚拟机 #

 

如果您需要转换在远程主机上运行的 Xen 虚拟机，此方法非常有用。因为 virt-v2v 通过 ssh 连接到远程主机，需确保主机上在运行 SSH 服务。

注意：无口令 SSH 访问

从 SLES 12 SP2 开始，virt-v2v 要求通过无口令 SSH 方式连接到远程主机。这意味着需向 ssh-agent 添加一个使用 SSH 密钥的连接。有关这方面的细节，请参见 man ssh-keygen 和 man ssh-add。第 18 章 “SSH：安全性网络操作” 上也提供了详细信息。

要连接到远程 libvirt 连接，请构建远程主机的相关有效连接 URI。在下面的示例中，远程主机名为 remote_host.example.com，连接的用户名为 root。连接 URI 的格式如下所示：

xen+ssh://root@remote_host.example.com/

有关 libvirt 连接 URI 的详细信息，请参见 http://libvirt.org/uri.html。

1. 确定您要转换的远程虚拟机的 libvirt 域名。

   root # virsh -c xen+ssh://root@remote_host.example.com/ list
    Id    Name                           State
   ----------------------------------------------------
     1     sles12_xen                     running
   [...]

   sles12_xen 是要转换的源虚拟机。

2. 远程连接的 virt-v2v 命令如下所示：

   root # virt-v2v sles12_xen \
   -i libvirt \
   -ic xen+ssh://root@remote_host.example.com/ \
   -os local_storage_pool \
   --bridge br0

1.5 运行转换的虚拟机 #

 

virt-v2v 成功完成之后，将采用 -on 选项指定的名称创建一个新的 libvirt 域。如果您未指定 -on，将使用与源虚拟机相同的名称。您可以使用 virsh 或虚拟机管理器等标准 libvirt 工具管理新 Guest。

提示：重引导计算机

如果您已按第 1.4.2 节 “基于 libvirt 域名的转换”中所述在 Xen 下完成转换，可能需要重引导主机，并使用非 Xen 内核进行引导。

有关 libvirt 的详细信息，请参见 http://libvirt.org。

http://libvirt.org/formatdomain.html 上提供了有关 libvirt XML 格式的更多细节。

https://documentation.suse.com/ 上的 SUSE Linux Enterprise Server 文档中提供了有关 Xen 和 KVM 虚拟化的详细信息。

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