linux中KVM 虚拟机增加硬盘例子
方法一、常规方式
采用模板的方式可能导致虚拟机的硬盘容量不够，可以通过单独增加一块硬盘来作为数据的存储。
1、首先使用dd命令在默认路径下创建一个大小为10G的映像文件：
dd bs=1M count=10240 if=/dev/zero of=/var/lib/libvirt/images/guest1_data.img
另外也可以使用 qemu-img 命令来创建，具体可以参考:centos 6.6 安装 KVM 虚拟机。
2、使用virsh edit 命令来编辑 domain 的配置文件，在其中已有的disk 段后增加如下内容：
3、分区格式化以及自动挂载硬盘
使用fdisk -l 查看系统的硬盘，根据上次配置，应该可以看到设备 /dev/sdb，然后使用如下命令进行分区
fdisk /dev/sdb
然后进行格式化
mkfs.ext4 /dev/sdb1
假设把新的硬盘mount 到 /data 目录，可以采用命令
mount /dev/sdb1 /data
这种方式如果机器重启后就需要重新mount，所以可以把他加入到fstab 中，这样系统启动时就能自动mount上去
/dev/sdb1 /data ext4 defaults 0 0
方法二、直接拉升分区
思 路，采用挂载的方法是而外添加了一块盘，有没有一种方法可以直接对硬盘进行拉伸。qemu-img中提供了一个resize的命令，但是该命令只是单纯的 简单了拉升或者缩小了一个raw的img镜像大小，对于其中的分区却不能进行修改。我需要对其中的的分区进行拓展。很碰巧红帽子提供这种插件可以时间。此方法是采用红帽子自带的插件virt-resize进行拓展。该命令首先是获取原来的分区信息，还 有其他文件信息。然后对新的镜像进行重新分区、格式化。最后拷贝原镜像中的文件到新文件系统中，再用新拓展的镜像替换原有镜像。因为实际采用copy的方 式，所以他花的时间比较长，如果是一个大镜像不建议使用此方法
具体解决方案。
前提安装libguestfs-tools工具包。关闭虚拟机
#yum -y install libguestfs-tools
A，新建一个大镜像
#qemu-img create -f raw test_extend.img 15G
注意，这里的img大小是你需要拓展的总大小
B，使用virt-resize进行拉升分区
#virt-resize —expand /dev/vda1 /var/lib/libvirt/images/test.img /var/lib/libvirt/images/test_new.img
注意，此时间很长，请耐心等待
C．使用新扩展的镜像代替原镜像
#mv /var/lib/libvirt/images/test_new.img /var/lib/libvirt/images/test.img
D，启动虚拟机
#virsh start test
拓展完成，
virt-resize的优势:能对虚拟机中的特定的分区进行拓展。并且能够拓展windows镜像。不需要登录到虚拟机里面进行任何操作。
缺点：拓展的时候需要关机。对于大的镜像，拓展的时间比较长。
对于LVM格式的虚拟机
如果你的硬盘格式支持LVM。那么你的硬盘拓展将容易许多，LVM支持硬盘的在线扩容。相当方便。
方法步骤：
#lvcreate -L 40G -n lv_vm_test1 VolGroup
#virsh attach-disk test /dev/mapper/VolGroup/lv_vm_test vdb
注意，有可能碰到权限问题。请先修改/dev/mapper/VolGroup/lv_vm_test的权限，是虚拟机可以挂载。
进入虚拟机的操作：
#pvcreate /dev/vdb
#vgextend VolGroup /dev/vdb
#vgs
#lvextend -l +100%FREE /dev/VolGroup/lv_root
#resize2fs -p /dev/VolGroup/lv_root
优势：拓展时间很快，支持动态扩展。
缺点，不适合window的拓展。
补充:
1. host增加物理硬盘并分区
HOST作为KVM的宿主计算机，管理所有GUEST虚拟机。我们通过给HOST增加物理硬盘，然后分给GUEST，从而实现给虚拟机硬盘扩容的效果。
如何给计算机增加物理硬盘并分区，请参考：多硬盘分区管理fdisk 文章
查看HOST机的硬盘
~ sudo fdisk -l
Disk /dev/sda: 299.4 GB, 299439751168 bytes
255 heads, 63 sectors/track, 36404 cylinders, total 584843264 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
Disk identifier: 0x000efd7c
Device Boot Start End Blocks Id System
/dev/sda1 2048 97656831 48827392 82 Linux swap / Solaris
/dev/sda2 97656832 136718335 19530752 83 Linux
/dev/sda3 136718336 214843335 39062500 83 Linux
/dev/sda4 * 214843392 215037951 97280 83 Linux
Disk /dev/sdb: 1999.3 GB, 1999307276288 bytes
255 heads, 63 sectors/track, 243068 cylinders, total 3904897024 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
Disk identifier: 0xf919a976
Device Boot Start End Blocks Id System
/dev/sdb1 2048 1952448511 976223232 7 HPFS/NTFS/exFAT
/dev/sdb2 1952448512 3904897023 976224256 5 Extended
/dev/sdb5 1952450560 2267023360 157286400+ 83 Linux
/dev/sdb6 2267025409 2581596160 157285376 83 Linux
/dev/sdb7 2581598209 2896168960 157285376 83 Linux
/dev/sdb8 2896171009 3210741760 157285376 83 Linux
/dev/sdb9 3210743809 3525314560 157285376 83 Linux
/dev/sdb10 3525316609 3904897023 189790207+ 83 Linux
~ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 37G 3.4G 32G 10% /
udev 24G 4.0K 24G 1% /dev
tmpfs 9.5G 1.1M 9.5G 1% /run
none 5.0M 8.0K 5.0M 1% /run/lock
none 24G 152K 24G 1% /run/shm
none 100M 28K 100M 1% /run/user
cgroup 24G 0 24G 0% /sys/fs/cgroup
/dev/sda2 19G 3.6G 14G 21% /home
/dev/sda4 92M 34M 54M 39% /boot
/dev/sdb1 931G 100G 832G 11% /disk/sdb1
/dev/sdb6 148G 188M 140G 1% /disk/sdb6
下面将进行两个测试：
通过virsh给guest增加文件硬盘：通过文件硬盘的镜像/disk/sdb6/c1d6.img
通过virsh给guest增加分区硬盘：直接使用分区硬盘/dev/sdb5
2. 通过virsh给guest增加文件硬盘
创建文件硬盘的镜像
~ cd /disk/sdb6/
~ sudo qemu-img create -f raw /disk/sdb6/c1d6.img 10G
Formatting '/disk/sdb6/c1d6.img', fmt=raw size=10737418240
~ ls -l
-rw-r--r-- 1 root root 10737418240 Jul 8 16:37 c1d6.img
drwx------ 2 root root 16384 Jul 8 09:03 lost+found/
通过virsh管理工具加载硬盘
~ sudo virsh
Welcome to virsh, the virtualization interactive terminal.
Type: 'help' for help with commands
'quit' to quit
#查看系统内的虚拟机
virsh # list
Id Name State
----------------------------------------------------
5 server3 running
6 server4 running
7 d2 running
8 r1 running
9 server2 running
12 c1 running
#在这里我们要对c1进行硬盘扩容
virsh # edit c1
#找到硬盘配置(原来的系统硬盘)
#增加文件硬盘,vdb
#保存退出
重启c1虚拟机
#请使用destroy命令，reboot和shutdown不管用。
~ virsh # destroy c1
Domain c1 destroyed
#list找不到c1
~ virsh # list
Id Name State
----------------------------------------------------
5 server3 running
6 server4 running
7 d2 running
8 r1 running
9 server2 running
#启动虚拟机c1
~ virsh # start c1
Domain c1 started
#进入虚拟机c1
~ console c1
在c1中，进行硬盘查检并分区
~ sudo fdisk -l
Disk /dev/vda: 42.9 GB, 42949672960 bytes
16 heads, 63 sectors/track, 83220 cylinders, total 83886080 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
Disk identifier: 0x000516aa
Device Boot Start End Blocks Id System
/dev/vda1 * 2048 499711 248832 83 Linux
/dev/vda2 501758 83884031 41691137 5 Extended
/dev/vda5 501760 83884031 41691136 8e Linux LVM
Disk /dev/vdb: 10.7 GB, 10737418240 bytes
16 heads, 63 sectors/track, 20805 cylinders, total 20971520 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
Disk identifier: 0x00000000
Disk /dev/vdb doesn't contain a valid partition table
Disk /dev/mapper/u1210-root: 38.4 GB, 38394658816 bytes
255 heads, 63 sectors/track, 4667 cylinders, total 74989568 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
Disk identifier: 0x00000000
Disk /dev/mapper/u1210-root doesn't contain a valid partition table
Disk /dev/mapper/u1210-swap_1: 4294 MB, 4294967296 bytes
255 heads, 63 sectors/track, 522 cylinders, total 8388608 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
Disk identifier: 0x00000000
Disk /dev/mapper/u1210-swap_1 doesn't contain a valid partition table
/dev/vdb已经被识别，接下来 分区,格式化,挂载,使用
硬盘分区
~ sudo fdisk /dev/vdb
Command (m for help): p
Disk /dev/vdb: 161.1 GB, 161061274112 bytes
16 heads, 63 sectors/track, 312076 cylinders, total 314572801 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
Disk identifier: 0x3b49c6a0
Device Boot Start End Blocks Id System
Command (m for help): n
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): p
Partition number (1-4, default 1):
Using default value 1
First sector (2048-314572800, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-314572800, default 314572800):
Using default value 314572800
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
#分区生效
~ sudo partprobe
~ sudo fdisk -l
Disk /dev/vdb: 10.7 GB, 10737418240 bytes
2 heads, 17 sectors/track, 616809 cylinders, total 20971520 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
Disk identifier: 0xf0432cd6
Device Boot Start End Blocks Id System
/dev/vdb1 2048 20971519 10484736 83 Linux
格式化
~ sudo mkfs -t ext4 /dev/vdb1
mke2fs 1.42.5 (29-Jul-2012)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe blocks
9830400 inodes, 39321344 blocks
1966067 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
1200 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
挂载
~ sudo mount /dev/vdb1 /home/cos/hadoopb
~ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/u1210-root 36G 1.1G 33G 4% /
udev 2.0G 4.0K 2.0G 1% /dev
tmpfs 791M 232K 791M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 2.0G 0 2.0G 0% /run/shm
none 100M 0 100M 0% /run/user
/dev/vda1 228M 29M 188M 14% /boot
/dev/vdb1 9.9G 151M 9.2G 2% /home/cos/hadoopb
使用
/home/cos/hadoopb的目录，已经挂载到了/dev/vdb1上面，我可以在hadoopb下载做任何的操作。
3. 通过virsh给guest增加分区硬盘
直接使用HOST的分区硬盘/dev/sdb5，做个虚拟机c1的分区
virsh # edit c1
#新增新硬盘vbc
virsh # destroy c1
Domain c1 destroyed
virsh # start c1
Domain c1 started
virsh # console c1
登陆虚拟c1，查看硬盘信息
sudo fdisk -l
[sudo] password for cos:
Disk /dev/vda: 42.9 GB, 42949672960 bytes
16 heads, 63 sectors/track, 83220 cylinders, total 83886080 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
Disk identifier: 0x000516aa
Device Boot Start End Blocks Id System
/dev/vda1 * 2048 499711 248832 83 Linux
/dev/vda2 501758 83884031 41691137 5 Extended
/dev/vda5 501760 83884031 41691136 8e Linux LVM
Disk /dev/vdb: 10.7 GB, 10737418240 bytes
2 heads, 17 sectors/track, 616809 cylinders, total 20971520 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
Disk identifier: 0xf0432cd6
Device Boot Start End Blocks Id System
/dev/vdb1 2048 20971519 10484736 83 Linux
Disk /dev/vdc: 161.1 GB, 161061274112 bytes
4 heads, 4 sectors/track, 19660800 cylinders, total 314572801 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
Disk identifier: 0x3b49c6a0
Device Boot Start End Blocks Id System
/dev/vdc1 2048 314572800 157285376+ 83 Linux
Disk /dev/mapper/u1210-root: 38.4 GB, 38394658816 bytes
255 heads, 63 sectors/track, 4667 cylinders, total 74989568 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
Disk identifier: 0x00000000
Disk /dev/mapper/u1210-root doesn't contain a valid partition table
Disk /dev/mapper/u1210-swap_1: 4294 MB, 4294967296 bytes
255 heads, 63 sectors/track, 522 cylinders, total 8388608 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
Disk identifier: 0x00000000
Disk /dev/mapper/u1210-swap_1 doesn't contain a valid partition table
已经被正确识别
Disk /dev/vdc: 161.1 GB, 161061274112 bytes
接下来，可以参考上面类似的过程，分区，格式化，挂载，使用
