關聯塊設備到虛擬機

關聯新的塊設備到KVM的虛擬機，運行以下命令

（1）創建個1GB的鏡像文件

root@kvm:~# dd if=/dev/zero of=/tmp/new_disk.img bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 0.670831 s, 1.6 GB/s

（2）關聯1GB的鏡像作爲KVM實例的一個新的磁盤

root@kvm:~# virsh attach-disk kvm1 /tmp/new_disk.img vda --live
Disk attached successfully

（3）通過Console品連接KVM的實例

root@kvm:~# virsh console kvm1
Connected to domain kvm1
Escape character is ^]

Debian GNU/Linux 8 debian ttyS0

debian login: root
Password:
...

（4）顯示kernel 環的buffer信息和查檢新塊的設備

root@debian:~# dmesg | grep vda
[ 3664.134978] sd 2:0:2:0: [vda] 2097152 512-byte logical blocks: (1.07 GB/1.00 GiB)
[ 3664.135248] sd 2:0:2:0: [vda] Write Protect is off
[ 3664.135251] sd 2:0:2:0: [vda] Mode Sense: 63 00 00 08
[ 3664.135340] sd 2:0:2:0: [vda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 3664.138254] vda: unknown partition table
[ 3664.139008] sd 2:0:2:0: [vda] Attached SCSI disk

（5）檢查這個新的塊設備

root@debian:~# fdisk -l /dev/vda

Disk /dev/vda: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

（6）顯示Host OS的實例配置信息

root@kvm:~# virsh dumpxml kvm1
<domain type='kvm' id='23'>
...
 <devices>
   <emulator>/usr/bin/qemu-system-x86_64</emulator>
   <disk type='file' device='disk'>
     <driver name='qemu' type='raw'/>
     <source file='/tmp/kvm1.img'/>
     <target dev='hda' bus='ide'/>
     <alias name='ide0-0-0'/>
     <address type='drive' controller='0' bus='0' target='0' unit='0'/>
   </disk>
   <disk type='file' device='disk'>
     <driver name='qemu' type='raw'/>
     <source file='/tmp/new_disk.img'/>
     <target dev='vda' bus='scsi'/>
     <alias name='scsi0-0-2'/>
     <address type='drive' controller='0' bus='0' target='0' unit='2'/>
   </disk>
 </devices>
</domain>

（7） 獲取這個新磁盤的詳細信息

root@kvm:~# virsh domblkstat kvm1 vda
vda rd_req 119
vda rd_bytes 487424
vda wr_req 0
vda wr_bytes 0
vda flush_operations 0
vda rd_total_times 29149092
vda wr_total_times 0
vda flush_total_times 0

（8）分離磁盤

root@kvm:~# virsh detach-disk kvm1 vda --live
Disk detached successfully

（9）複製或創建新的raw鏡像

root@kvm:~# cp /tmp/new_disk.img /tmp/other_disk.img

（10）寫下的配置文件

root@kvm:~# cat other_disk.xml
<disk type='file' device='disk'>
 <driver name='qemu' type='raw' cache='none'/>
 <source file='/tmp/other_disk.img'/>
 <target dev='vdb'/>
</disk>

（11）關聯新的設備

root@kvm:~# virsh attach-device kvm1 --live other_disk.xml
Device attached successfully

（12）分離塊設備

root@kvm:~# virsh detach-device kvm1 other_disk.xml --live
Device detached successfully