由于刚开始做磁盘空间规划时，失误给根分区分配磁盘较小，导致后续实验环境无法进行，所以在经过研究后，决定尝试增加根分区的磁盘空间，注意这仅适用于创建在 LVM 上的文件系统。
实验环境
- Parallels Desktop 12
- CentOS 6.9
- 根分区空间 6.5GB
- 已使用 5.8GB
- 预计 增加 12G 磁盘空间
增加一块物理磁盘
Parallels Desktop 不能在线增加磁盘，所以要先将 VM 关闭，然后添加： 
增加 12G 的磁盘 
然后启动 VM，这时可以通过fdisk -l查看当前已经增加了一块 12G 的磁盘
格式化磁盘并加入到 VGroup 组内
查看当前pvdisplay磁盘列表，将/dev/sdb创建 pv 块
bash
[root@centos ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name vg_hadoop01
PV Size 7.51 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 1922
Free PE 0
Allocated PE 1922
PV UUID MUCrDa-eJpZ-EXwE-YwwM-S2Az-p2m7-K9q3Fo
[root@centos ~]# pvcreate /dev/sdb
Physical volume "/dev/sdb" successfully created
[root@centos ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name vg_hadoop01
PV Size 7.51 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 1922
Free PE 0
Allocated PE 1922
PV UUID MUCrDa-eJpZ-EXwE-YwwM-S2Az-p2m7-K9q3Fo
--- Physical volume ---
PV Name /dev/sdb
VG Name vg_hadoop01
PV Size 12.00 GiB / not usable 4.00 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 3071
Free PE 3071
Allocated PE 0
PV UUID XTpaBR-512W-vQIV-fwwz-So7L-ZCa3-yjDccQ查看当前vgdisplayVGroup 组，将/dev/sdb加入根目录所在 VGroup
sh
[root@centos ~]# vgdisplay
--- Volume group ---
VG Name vg_hadoop01
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size 7.51 GiB
PE Size 4.00 MiB
Total PE 1922
Alloc PE / Size 1922 / 7.51 GiB
Free PE / Size 0 / 0
VG UUID szQ4fH-Sr1Z-V6c2-KVMp-ZUik-oUDP-rU8dQS
[root@centos ~]# vgextend vg_hadoop01 /dev/sdb
Volume group "vg_hadoop01" successfully extended
[root@centos ~]# vgdisplay
--- Volume group ---
VG Name vg_hadoop01
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 4
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 2
Act PV 2
VG Size 19.50 GiB
PE Size 4.00 MiB
Total PE 4993
Alloc PE / Size 1922 / 7.51 GiB
Free PE / Size 3071 / 12.00 GiB
VG UUID szQ4fH-Sr1Z-V6c2-KVMp-ZUik-oUDP-rU8dQS查看lvdisplay根卷的名称，将磁盘加入根卷的 LV
bash
[root@centos ~]# lvdisplay
--- Logical volume ---
LV Path /dev/vg_hadoop01/lv_root
LV Name lv_root
VG Name vg_hadoop01
LV UUID tJDetu-Theq-BQ5g-3ZFe-Gan7-1SSv-OHeYrH
LV Write Access read/write
LV Creation host, time hadoop01, 2017-04-18 07:09:58 +0800
LV Status available
# open 1
LV Size 6.71 GiB
Current LE 1718
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
--- Logical volume ---
LV Path /dev/vg_hadoop01/lv_swap
LV Name lv_swap
VG Name vg_hadoop01
LV UUID D4K7I6-tPO0-HMbC-VWkR-2HV4-WjAe-M82wYq
LV Write Access read/write
LV Creation host, time hadoop01, 2017-04-18 07:09:59 +0800
LV Status available
# open 1
LV Size 816.00 MiB
Current LE 204
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
[root@centos ~]# lvextend -l +100%FREE /dev/vg_hadoop01/lv_root
Size of logical volume vg_hadoop01/lv_root changed from 6.71 GiB (1718 extents) to 18.71 GiB (4789 extents).
Logical volume lv_root successfully resized.
[root@centos ~]# lvdisplay
--- Logical volume ---
LV Path /dev/vg_hadoop01/lv_root
LV Name lv_root
VG Name vg_hadoop01
LV UUID tJDetu-Theq-BQ5g-3ZFe-Gan7-1SSv-OHeYrH
LV Write Access read/write
LV Creation host, time hadoop01, 2017-04-18 07:09:58 +0800
LV Status available
# open 1
LV Size 18.71 GiB
Current LE 4789
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
--- Logical volume ---
LV Path /dev/vg_hadoop01/lv_swap
LV Name lv_swap
VG Name vg_hadoop01
LV UUID D4K7I6-tPO0-HMbC-VWkR-2HV4-WjAe-M82wYq
LV Write Access read/write
LV Creation host, time hadoop01, 2017-04-18 07:09:59 +0800
LV Status available
# open 1
LV Size 816.00 MiB
Current LE 204
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1更新磁盘分区表
当你增加完成之后，这时使用df -h查看的磁盘空间仍然没有变化，因为我们还需要将根卷的分区表刷新。
使用resize2fs刷新根卷信息
bash
[root@centos ~]# resize2fs /dev/vg_hadoop01/lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg_hadoop01/lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/vg_hadoop01/lv_root to 4903936 (4k) blocks.
The filesystem on /dev/vg_hadoop01/lv_root is now 4903936 blocks long.
[root@centos ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_hadoop01-lv_root
19G 5.8G 12G 33% /
tmpfs 244M 0 244M 0% /dev/shm
/dev/sda1 477M 52M 400M 12% /boot