根文件系统快用完了，给你一块新硬盘，怎样实现根文件系统扩容？这是面试中经常会出现的一个问题。接下来，我们就在虚拟机里面做一下这个试验。
1、试验环境
物理机：Windows XP
虚拟机：VMware 7
虚拟系统：RHEL 4
2、当前的磁盘使用情况
三块SCSI虚拟硬盘，每个8G，总共24G。一个卷组VolGroup00，分成两个逻辑卷，LogVol00作为根文件系统，LogVol01作为swap。
[root@Shell_HAT]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
20G 17G 1.9G 91% /
/dev/sda1 99M 9.0M 85M 10% /boot
none 506M 0 506M 0% /dev/shm
LVM添加硬盘和扩容
测试环境：CentOS7 64位（KVM虚拟机）
LVM版本：lvm2-2.02.105-14.el7.x86_64
1、添加一块硬盘（8GB）到系统中
使用 fdisk -l 查看到这块新盘为/dev/vdb：
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shell
# fdisk -l
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2、对新盘分区
使用 fdisk 命令对新盘进行分区，这里建立了一个主分区/dev/vdb1，大小8GB，最后使用 partprobe 命令重新读取分区表：
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shell
# fdisk /dev/vdb
shell
# partprobe
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在分区的过程中，注意设置格式为8e，这是LVM的分区格式。
[root@Shell_HAT]# ls -l /dev/sd*
brw-rw---- 1 root disk 8, 0 Mar 11 2012 /dev/sda
brw-rw---- 1 root disk 8, 1 Mar 11 2012 /dev/sda1
brw-rw---- 1 root disk 8, 2 Mar 11 2012 /dev/sda2
brw-rw---- 1 root disk 8, 16 Mar 11 2012 /dev/sdb
brw-rw---- 1 root disk 8, 17 Mar 11 2012 /dev/sdb1
brw-rw---- 1 root disk 8, 32 Mar 11 2012 /dev/sdc
brw-rw---- 1 root disk 8, 33 Mar 11 2012 /dev/sdc1
[root@Shell_HAT]# fdisk -l
Disk /dev/sda: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 1044 8281507 8e Linux LVM
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 1044 8385898 8e Linux LVM
Disk /dev/sdc: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc1 1 1044 8385898 8e Linux LVM
[root@Shell_HAT]# vgdisplay
--- Volume group ---
VG Name VolGroup00
System ID
Format lvm2
Metadata Areas 3
Metadata Sequence No 17
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 3
Act PV 3
VG Size 23.81 GB
PE Size 32.00 MB
Total PE 762
Alloc PE / Size 760 / 23.75 GB
Free PE / Size 2 / 64.00 MB
VG UUID djJXj5-3rkx-PEpi-2OJn-ZofS-VaF6-KUo9UR
[root@Shell_HAT]# lvdisplay
--- Logical volume ---
LV Name /dev/VolGroup00/LogVol00
VG Name VolGroup00
LV UUID kOehzE-SEAQ-tm3L-jIkG-gbZv-YWC5-apQWWf
LV Write Access read/write
LV Status available
# open 1
LV Size 19.81 GB
Current LE 634
Segments 4
Allocation inherit
Read ahead sectors 0
Block device 253:0
--- Logical volume ---
LV Name /dev/VolGroup00/LogVol01
VG Name VolGroup00
LV UUID vI2EKQ-5tne-heGk-bbkL-9K6g-23fs-b9e3Y4
LV Write Access read/write
LV Status available
# open 1
LV Size 3.94 GB
Current LE 126
Segments 2
Allocation inherit
Read ahead sectors 0
Block device 253:1
[root@Shell_HAT]# cat /etc/fstab
# This file is edited by fstab-sync - see 'man fstab-sync' for details
/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
/dev/VolGroup00/LogVol01 swap swap defaults 0 0
3、在VMware里面新增一块SCSI虚拟硬盘
确认虚拟系统RHEL4处于关机状态，用VMware打开Red Hat Enterprise Linux 4.vmx，点击Edit virtual machine setings，点击Add按钮，选中Hard Disk，点击Next按钮，选中Create a new virtual disk，点击Next按钮，选中SCSI，点击Next按钮，设置Maximum disk size为8，点击Next按钮，点击Finish按钮，点击OK按钮，启动虚拟系统RHEL4。
4、根文件系统扩容
用一句话来总结：创建物理卷 >>> 卷组扩容 >>> 逻辑卷扩容 >>> 文件系统扩容
（1）创建物理卷
[root@Shell_HAT]# pvcreate /dev/sdd
Physical volume "/dev/sdd" successfully created
（2）查看创建好的物理卷
[root@Shell_HAT]# pvdisplay /dev/sdd
--- NEW Physical volume ---
PV Name /dev/sdd
VG Name
PV Size 8.00 GB
Allocatable NO
PE Size (KByte) 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID 5ne1Nx-bsCO-9Vxh-6Pmc-rBnf-dsZo-WjQDYS
（3）卷组扩容
[root@Shell_HAT]# vgextend VolGroup00 /dev/sdd
Volume group "VolGroup00" successfully extended
（4）查看扩容之后的卷组信息
[root@Shell_HAT]# vgdisplay
--- Volume group ---
VG Name VolGroup00
System ID
Format lvm2
Metadata Areas 4
Metadata Sequence No 18
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 4
Act PV 4
VG Size 31.78 GB
PE Size 32.00 MB
Total PE 1017
Alloc PE / Size 760 / 23.75 GB
Free PE / Size 257 / 8.03 GB
VG UUID djJXj5-3rkx-PEpi-2OJn-ZofS-VaF6-KUo9UR
（5）逻辑卷扩容
[root@Shell_HAT]# lvextend -L+8G /dev/VolGroup00/LogVol00
Extending logical volume LogVol00 to 27.81 GB
Logical volume LogVol00 successfully resized
（6）查看扩容之后的逻辑卷
[root@Shell_HAT]# lvdisplay /dev/VolGroup00/LogVol00
--- Logical volume ---
LV Name /dev/VolGroup00/LogVol00
VG Name VolGroup00
LV UUID kOehzE-SEAQ-tm3L-jIkG-gbZv-YWC5-apQWWf
LV Write Access read/write
LV Status available
# open 1
LV Size 27.81 GB
Current LE 890
Segments 5
Allocation inherit
Read ahead sectors 0
Block device 253:0
（7）文件系统在线扩容
[root@Shell_HAT]# resize2fs /dev/VolGroup00/LogVol00
ext2online v1.1.18 - 2001/03/18 for EXT2FS 0.5b
（8）大功告成
[root@Shell_HAT]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
28G 17G 9.4G 65% /
/dev/sda1 99M 9.0M 85M 10% /boot
none 506M 0 506M 0% /dev/shm
