KVM虚拟磁盘扩容
1、磁盘扩容分为raw和qcow2两种扩容方式，命令相同，区别是后缀名
[root@daixuan ~]# qemu-img info /data/daixuan1.qcow2 //本身只有9G
p_w_picpath: /data/daixuan1.qcow2
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 10G
cluster_size: 65536
[root@daixuan ~]# qemu-img resize /data/daixuan1.qcow2 +5G //加5G
Image resized.
[root@daixuan ~]# qemu-img info /data/daixuan1.qcow2 //查看已经+5G，登录后fdisk -l还是10G
p_w_picpath: /data/daixuan1.qcow2
file format: qcow2
virtual size: 15G (16106127360 bytes)
如果需要真正生效，需要destroy，之后start，把配置重新加载
[root@daixuan ~]# virsh destroy daixuan1
[root@daixuan ~]# virsh start daixuan1
[root@daixuan ~]# virsh console daixuan1
fdisk -l 列出系统中所有的磁盘设备和分区表，这里磁盘设备容量已经增加5G
[root@localhost ~]# fdisk -l
Disk /dev/vda: 16.1 GB, 16106127360 bytes
2、但是磁盘挂载的空间并没有增加，依然是8.3G
[root@localhost ~]# df -h //查看可用磁盘总容量和使用容量
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 8.3G 685M 7.2G 9% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/vda1 477M 33M 419M 8% /boot
（1）因为新增加的空间还没有划分使用，所以要继续分区：
[root@localhost ~]# fdisk /dev/vda
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help): p
Disk /dev/vda: 16.1 GB, 16106127360 bytes
16 heads, 63 sectors/track, 31207 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000dca27
Device Boot Start End Blocks Id System
/dev/vda1 * 3 1018 512000 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/vda2 1018 20806 9972736 8e Linux LVM
Partition 2 does not end on cylinder boundary.
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (1-31207, default 1): 20807
Last cylinder, +cylinders or +size{K,M,G} (20807-31207, default 31207): 31207
Command (m for help): p
Disk /dev/vda: 16.1 GB, 16106127360 bytes
16 heads, 63 sectors/track, 31207 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000dca27
Device Boot Start End Blocks Id System
/dev/vda1 * 3 1018 512000 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/vda2 1018 20806 9972736 8e Linux LVM
Partition 2 does not end on cylinder boundary.
/dev/vda3 20807 31207 5242104 83 Linux
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
（2）然后再把这个/dev/vda3 加入到lvm里面去：
[root@localhost ~]# ls /dev/vda3 //如果没有这个分区，需要重启一下
[root@localhost ~]# reboot
[root@localhost ~]# pvcreate /dev/vda3 //创建物理卷
Physical volume "/dev/vda3" successfully created
[root@localhost ~]# pvs //查看卷
PV VG Fmt Attr PSize PFree
/dev/vda2 VolGroup lvm2 a-- 9.51g 0
/dev/vda3 lvm2 --- 5.00g 5.00g
[root@localhost ~]# vgextend VolGroup /dev/vda3 //VolGroup虚拟卷扩展，vda3加入到Vol
Volume group "VolGroup" successfully extended
[root@localhost ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 VolGroup lvm2 a-- 9.51g 0
/dev/vda3 VolGroup lvm2 a-- 5.00g 0
[root@localhost ~]# vgs //VFree中5G
VG #PV #LV #SN Attr VSize VFree
VolGroup 2 2 0 wz--n- 14.50g 5.00g
如何把5G加入到lv_root中？
[root@localhost ~]# lvs //查看逻辑卷
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lv_root VolGroup -wi-ao---- 8.54g
lv_swap VolGroup -wi-ao---- 992.00m
[root@localhost ~]# lvextend -l +100%FREE /dev/VolGroup/lv_root //扩展卷
Size of logical volume VolGroup/lv_root changed from 8.54 GiB (2186 extents) to 13.54 GiB (3465 extents).
Logical volume lv_root successfully resized
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 8.3G 685M 7.2G 9% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/vda1 477M 33M 419M 8% /boot
[root@localhost ~]# resize2fs /dev/VolGroup/lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/VolGroup/lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/VolGroup/lv_root to 3548160 (4k) blocks.
The filesystem on /dev/VolGroup/lv_root is now 3548160 blocks long.
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 14G 687M 12G 6% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/vda1 477M 33M 419M 8% /boot
如果提示 This p_w_picpath format does not support resize, 检查一下你qemu-img create的时候，是否有加 preallocation=metadata 选项，如果有，就不能resize了。
（3）另外，如果是增加磁盘，思路是
创建磁盘： qemu-img create -f qcow2 /data/daixuan1_2.qcow2 5G
关闭虚拟机： virsh destroy daixuan1
编辑配置文件： virsh edit daixuan1
复制增加如下：注意是vdb，qcow2
<disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/data/daixuan1_2.qcow2'/> <target dev='vdb' bus='virtio'/> </disk>
开启虚拟机：virsh start daixuan1
进入虚拟机：virsh console daixuan1
分区： fdisk /dev/vdb
格式化：mkfs.ext4 /dev/vdb
挂载：vim /etc/fstab，添加一行：/dev/vdb /mnt ext4 defaults 0 0
mount -a 然后mnt就可以使用了
[root@localhost ~]# cd /mnt
[root@localhost mnt]# touch 23.txt
当然也可以按照上面的思路把 /dev/vdb 加入到 lvm里面去，测试成功，这里省略步骤
注： raw格式
步骤基本上和qcow2一样。如果提示 This p_w_picpath format does not support resize, 检查一下你qemu-img create的时候，是否有加 preallocation=metadata 选项，如果有，就不能resize了。
