kvm虚拟机磁盘扩容

发表于 2018-04-13 更新于 2022-01-09 分类于 solutions

kvm虚拟机的磁盘空间告急，怎么有效进行扩容。

kvm的磁盘格式分为：raw磁盘格式和qcow2磁盘格式，扩充的思路如下:

假如对raw格式的 centos6.6.img 直接扩展：

1	qemu-img info centos6.6.img

image: centos6.6.img
file format: raw
virtual size: 16G (17179869184 bytes)
disk size: 16G

1	qemu-img resize centos6.6.img +10G

image: centos6.6.img
file format: raw
virtual size: 26G (27917287424 bytes)
disk size: 16G

开启虚拟机，然后查看磁盘空间。

df -h

Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       14G   13G  521M  97% /
tmpfs                 940M   76K  940M   1% /dev/shm
/dev/sda1             477M  150M  299M  34% /boot

fdisk -l

Disk /dev/sda: 27.9 GB, 27917287424 bytes
255 heads, 63 sectors/track, 3394 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0003d6ba

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        2089    16264192   8e  Linux LVM

Disk /dev/mapper/VolGroup-lv_root: 14.9 GB, 14935916544 bytes
255 heads, 63 sectors/track, 1815 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000


Disk /dev/mapper/VolGroup-lv_swap: 1715 MB, 1715470336 bytes
255 heads, 63 sectors/track, 208 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

可见，实际的物理空间 /dev/sd 已经扩容为27.9GB，但是真正的使用空间还是16GB。

开始分区并保存。

[root@localhost Desktop]# fdisk /dev/sda

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): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (2089-3394, default 2089): 
Using default value 2089
Last cylinder, +cylinders or +size{K,M,G} (2089-3394, default 3394): 
Using default value 3394

Command (m for help): t
Partition number (1-4): 3
Hex code (type L to list codes): 8e
Changed system type of partition 3 to 8e (Linux LVM)

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.

重启该虚拟机，接下来开始创建物理卷，加入卷组，扩展逻辑卷。

[root@localhost Desktop]# pvs
  PV         VG       Fmt  Attr PSize  PFree
  /dev/sda2  VolGroup lvm2 a--  15.51g    0 
[root@localhost Desktop]# vgextend VolGroup /dev/sda
sda   sda1  sda2  sda3  
[root@localhost Desktop]# vgextend VolGroup /dev/sda3
  Physical volume "/dev/sda3" successfully created
  Volume group "VolGroup" successfully extended
[root@localhost Desktop]# lvextend -l +100%FREE /dev/VolGroup/lv_root 
  Size of logical volume VolGroup/lv_root changed from 13.91 GiB (3561
extents) to 23.91 GiB (6120 extents).
  Logical volume lv_root successfully resized
[root@localhost Desktop]# 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 = 2
Performing an on-line resize of /dev/VolGroup/lv_root to 6266880 (4k) blocks.
The filesystem on /dev/VolGroup/lv_root is now 6266880 blocks long.

[root@localhost Desktop]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       24G   13G   10G  56% /
tmpfs                 940M  224K  940M   1% /dev/shm
/dev/sda1             477M  150M  299M  34% /boot

成功扩容。

参考 KVM虚拟化笔记（十）------kvm虚拟机扩充磁盘空间