kvm快照
# virsh shutdown kvm1
# qemu-img info /var/lib/libvirt/images/kvm1.img ----raw格式是不支持snapshot功能，所以我们需要转换成象qcow2这种支持snapshot功能的格式（rhel7,cenots7已经默认是qcow2格式了)
image: /var/lib/libvirt/images/kvm1.img
file format: raw
virtual size: 20G (21474836480 bytes)
disk size: 6.5G
# cd /var/lib/libvirt/images/
# qemu-img convert -f raw -O qcow2 kvm1.img kvm1.qcow2.img
----把磁盘格式由raw转换为qcow2
# ll -h kvm1* ----qcow2格式占用空间小
# virsh edit kvm1 ----编辑kvm1虚拟的主配置文件,把raw磁盘换成qcow2磁盘
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/> ----把type里的row改成qcow2
<source file='/var/lib/libvirt/images/kvm1.qcow2.img'/> ----把路径也改成转换为qcow2格式的文件路径
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</disk>
# virsh define kvm1.xml
# virsh start kvm1 ----再启动,使他生效
# rm -rf /var/lib/libvirt/images/kvm1.img ----可以把原来的raw格式的磁盘文件给删除掉
# virsh help snapshot ----查看和快照操作有关的命令
# virsh snapshot-list kvm1 ----列快照,默认没有
Name Creation Time State
------------------------------------------------------------
# virsh snapshot-create-as --domain kvm1 snap1 --description "my first test snapshot" ----对kvm1创建一个叫snap1的快照
# /var/lib/libvirt/qemu/snapshot/kvm1/ ----默认快照的保存位置
# virsh snapshot-list kvm1
Name Creation Time State
------------------------------------------------------------
snap1 2017-04-21 09:56:47 +0800 running
查看帮助
# virsh help snapshot
查看快照配置
# virsh snapshot-current kvm1
恢复快照
# virsh snapshot-revert kvm1 snap1
删除快照
# virsh snapshot-delete kvm1 snap1
--恢复快照时报错:error: revert requires force: Target controller type ide does not match source usb
表示kvm不能在线恢复，需要关闭虚拟机，再恢复快照。如果你要在线恢复快照，需要加一个--force的参数
写法如:
# virsh snapshot-revert kvm1 snap1 --force
恢复快照的时间较长，恢复完后，键盘操作会有些问题，可以把它重启一下
# virsh destroy kvm1
# virsh start kvm1
==========================
在rhel7和centos7下使用快照非常方便，速度也快很多
主要记住下面几条命令就ok
# virsh snapshot-list kvm1
# virsh snapshot-create-as --domain kvm1 snap1 --description "my first test snapshot"
# virsh snapshot-revert kvm1 snap1
# virsh snapshot-delete kvm1 snap1