# Linux KVM在线迁移实战 KVM热迁移实现需要使用共享的存储池，最简便的方法是使用NFS共享。更为复杂且高可用、高性能的是使用共享的分布式文件系统，如Ceph。 > 本实践采用CentOS 7系统构建的NFS服务作为共享存储 ## 构建NFS共享存储 > 以下操作在作为NFS服务的主机上执行 * NFS服务器上创建共享目录 ``` mkdir -p /var/lib/nfs-data/images ``` * 使用以下命令安装 NFS 支持 ``` yum install nfs-utils nfs-utils-lib ``` * 设置nfs相关服务在操作系统启动时启动 ``` systemctl enable rpcbind systemctl enable nfs-server systemctl enable nfs-lock systemctl enable nfs-idmap ``` * 启动nfs服务 ``` systemctl start rpcbind systemctl start nfs-server systemctl start nfs-lock systemctl start nfs-idmap ``` * 服务器端设置NFS卷输出，即编辑 `/etc/exports` 添加： ``` /var/lib/nfs-data/images 192.168.1.0/24(rw,sync,no_root_squash,no_subtree_check) ``` * 服务器端输出NFS ``` exportfs -a ``` ## NFS客户端挂载 * 编辑需要挂载共享NFS磁盘的设置`/etc/fstab`配置将共享NFS卷挂载到`/var/lib/libvirt/nfs-images` ``` 192.168.1.1:/var/lib/nfs-data/images /var/lib/libvirt/nfs-images nfs auto,rw,vers=3,hard,intr,tcp,rsize=32768,wsize=32768 0 0 ``` * 客户端挂载 ``` mkdir -p /var/lib/libvirt/nfs-images mount /var/lib/libvirt/nfs-images ``` > 所有使用共享存储的KVM主机都挂载好这个NFS共享 ## 配置libvirt的VM存储池 将默认的`/var/lib/libvirt/images`目录对应的`default`存储池修改到新的共享存储 * 先关闭运行的虚拟机 ``` virsh shutdown centos7 virsh shutdown win2012 ``` * 检查所有虚拟机运行状态，确保所有虚拟机都已经关闭 ``` virsh list --all ``` * 检查存储池 ``` virsh pool-list ``` 显示输出 ``` Name State Autostart ------------------------------------------- huatai active yes images active yes root active yes ``` * 检查存储池信息 - 可以看到存储池容量 ``` virsh pool-info images ``` * 检查存储池路径 ``` virsh pool-dumpxml images | grep -i path ``` 输出显示 ``` /var/lib/libvirt/images ``` * 检查有哪些VM镜像存储在这个路径中 ``` virsh vol-list images ``` 输出显示 ``` Name Path ------------------------------------------------------------------------------ CentOS-7-x86_64-DVD-1511.iso /var/lib/libvirt/images/CentOS-7-x86_64-DVD-1511.iso centos7.img /var/lib/libvirt/images/centos7.img win2012.img /var/lib/libvirt/images/win2012.img win2012.iso /var/lib/libvirt/images/win2012.iso ``` * 停止存储池 ``` virsh pool-destroy images ``` * 编辑存储池配置 ``` virsh pool-edit images ``` 编辑内容，将其中的存储路径修改成新的NFS共享存储路径 ``` images 82b69f47-1c20-4e99-9dad-5665181c0d77 ... /var/lib/libvirt/nfs-images ... ``` * 启动存储池 ``` virsh pool-start images ``` * 再次检查存储路径 ``` virsh pool-dumpxml images | grep -i path ``` 确认修改路径正确 ``` /var/lib/libvirt/nfs-images ``` * 将VM镜像从旧路径迁移到新路径 ``` mv /var/lib/libvirt/images/* /var/lib/libvirt/nfs-images/ ``` * 编辑VM配置文件更新到新的存储池路径 ``` sudo virsh edit centos7 ``` 将存储路径修改到共享存储目录 ``` ``` * 然后启动虚拟机 ``` virsh start centos7 ``` ## KVM热迁移 * 测试环境：将虚拟机 `centos7` 从KVM物理服务器 `test-1-3` 迁移到 `test-1-4` 上，我们要先打通`test-1-3`登录到`test-1-4`的免密码ssh，并验证ssh登录无误 ``` ssh test-1-4 "virsh list" ``` 显示输出 ``` Id Name State ---------------------------------------------------- ``` * 在虚拟机内部启动ping，验证网络是否会有影响 * 从KVM主机，`test-1-3`上发起热迁移 ``` virsh migrate centos7 qemu+ssh://root@testtfs-1-4/system ``` 提示信息 ``` error: Unsafe migration: Migration may lead to data corruption if disks use cache != none ``` 要避免这个报错，需要关闭每个VM的disk I/O cache功能，即编辑vm ``` virsh shutdown centos7 virsh edit centos7 ``` 在 `driver`行添加\`cache='none' ```
``` 然后再次启动vm ``` virsh start centos7 ``` 然后再次迁移。 > 另外一种方法是使用 `--unsafe` ，这样对于非关键应用可以适合。 ``` virsh migrate centos7 qemu+ssh://root@testtfs-1-4/system --unsafe ``` * 然后在`test-1-4`物理服务器上可以看到迁移后正常运行的虚拟机 ``` [root@test-1-4 /root] #virsh list Id Name State ---------------------------------------------------- 1 centos7 running ``` ## 参考 * [十：更改libvirt虚拟机镜像存储路径](https://github.com/huataihuang/cloud-atlas-draft/tree/6f3204fffc11cf006abd394631e2598d98b415c3/virtual/kvm/startup/change_libvirt_vm_image_store_path/README.md) * [十一：实现Linux KVM在线迁移](https://github.com/huataihuang/cloud-atlas-draft/tree/6f3204fffc11cf006abd394631e2598d98b415c3/virtual/kvm/startup/perform_live_migration_on_linux_kvm/README.md) * [CentOS 7 NFS设置](https://github.com/huataihuang/cloud-atlas-draft/tree/6f3204fffc11cf006abd394631e2598d98b415c3/service/nfs/setup_nfs_on_centos7/README.md) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://huataihuang.gitbook.io/cloud-atlas-draft/virtual/kvm/startup/in_action/live_migration_kvm_vm_in_action.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.