1. 硬盘扩容
qcow2格式磁盘，直接通过qemu-img 直接扩展qcow2磁盘, 新添加一块qcow2 格式的磁盘加入到KVM虚拟机,然后通过虚拟机系统lvm逻辑卷管理方式进行管理,扩展磁盘空间。
添加一块qcow2磁盘
[root@yangrz01 isos]# qemu-img create -f qcow2 test01_add.qcow2 2G
Formatting 'test01_add.qcow2', fmt=qcow2 size=2147483648 encryption=off cluster_size=65536
添加一块qcow2磁盘信息加入配置文件
<devices>
<emulator>/usr/libexec/qemu-kvm</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source file='/home/work/isos/test2.img'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source file='/home/work/isos/test01_add.qcow2'/>
<target dev='vdb' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</disk> <disk type='block' device='cdrom'>
启动虚拟机并配置磁盘
[root@localhost ~]# fdisk -l
Disk /dev/vda: 7516 MB, 7516192768 bytes
16 heads, 63 sectors/track, 14563 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: 0x0006d29d
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 14564 6827008 8e Linux LVM
Partition 2 does not end on cylinder boundary.
Disk /dev/vdb: 2147 MB, 2147483648 bytes
16 heads, 63 sectors/track, 4161 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
发现新增的磁盘已经添加成功。
配置lvm扩展磁盘：
分区
[root@localhost ~]# fdisk /dev/vdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x4e991999.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-4161, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-4161, default 4161):
Using default value 4161
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
重读分区表
[root@localhost ~]# partx -a /dev/sdb
发现重读分区表可能会失败，查到的原因可能是因为虚拟机的缘故，条件允许可以重启虚拟机即可
扩展逻辑卷
[root@localhost ~]# pvcreate /dev/vdb1
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 5.8G 757M 4.7G 14% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/vda1 485M 32M 428M 7% /boot
[root@localhost ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 VolGroup lvm2 a-- 6.51g 0
/dev/vdb1 lvm2 a-- 2.00g 2.00g
[root@localhost ~]# vgextend VolGroup /dev/vdb1
Volume group "VolGroup" successfully extended
[root@localhost ~]# vgs
VG #PV #LV #SN Attr VSize VFree
VolGroup 2 2 0 wz--n- 8.50g 2.00g
[root@localhost ~]# lvextend -l +100%FREE /dev/VolGroup/lv_root
Extending logical volume lv_root to 7.80 GiB
Logical volume lv_root successfully resized
[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 2045952 (4k) blocks.
The filesystem on /dev/VolGroup/lv_root is now 2045952 blocks long.
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 7.7G 758M 6.6G 11% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/vda1 485M 32M 428M 7% /boot
df -h结果发现，磁盘扩容成功。
内存和CPU扩容，都是扩容完成后重启虚拟机即可生效。
CPU扩容
编辑虚拟机配置文件
[root@yangrz01 ~]# virsh edit oeltest02
<vcpu placement='static'>1</vcpu>
也可以改为自动扩容：
current="1">4</vcpu> #当前为1，自动扩容最大为4
内存扩容
[root@yangrz01 ~]# virsh edit oeltest02
<memory unit='KiB'>4194304</memory> #修改最大支持内存扩容为4G
<currentMemory unit='KiB'>1048576</currentMemory> #当前KVM虚拟机内存为1G
需要修改内存时，直接修改这两处即可。