参考网站：http://www.360doc.com/content/18/0128/11/52410512_725728162.shtml
VirtualBox中安装了CentOS 7，给同事用来做kafka和zookeeper测试服务器。昨晚kafka意外终止，看了日志发现是/root只分配了1GiB大小，已接近饱和。开始bing，总结一下步骤：
列出各分区使用情况：
# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos-root xfs 997M 994M 2.9M 100% /
devtmpfs devtmpfs 915M 0 915M 0% /dev
tmpfs tmpfs 921M 0 921M 0% /dev/shm
tmpfs tmpfs 921M 17M 905M 2% /run
tmpfs tmpfs 921M 0 921M 0% /sys/fs/cgroup
/dev/mapper/centos-usr xfs 4.9G 1.6G 3.4G 33% /usr
/dev/sda1 xfs 97M 66M 31M 69% /boot
/dev/mapper/centos-var xfs 2.4G 473M 1.9G 21% /var
可以看见 /dev/mapper/centos-root 已经使用了100%，我们准备为它扩容。
在VirtualBox中添加一块新的虚拟磁盘：
先关闭操作系统。在VirtualBox中选中当前VM，设置->存储->控制器->SATA控制器，点击图标“添加虚拟硬盘”，新建一个虚拟硬盘。我增加了一块3GiB大小的虚拟磁盘，保存后再次启动虚拟机。
创建新分区
先看一下现有磁盘情况：
# fdisk -l
结果：
Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 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 label type: dos
Disk identifier: 0x000940ec
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 206847 102400 83 Linux
/dev/sda2 206848 41943039 20868096 8e Linux LVM
Disk /dev/sdb: 3221 MB, 3221225472 bytes, 6291456 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 /dev/mapper/centos-swap: 2097 MB, 2097152000 bytes, 4096000 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 /dev/mapper/centos-usr: 5242 MB, 5242880000 bytes, 10240000 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 /dev/mapper/centos-root: 1048 MB, 1048576000 bytes, 2048000 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
...
...
...
已经可以看到新磁盘/dev/sdb。
对新磁盘进行分区：
# fdisk /dev/sdb
在fdisk的交互模式中，依次输入：
n --创建新分区
p --创建主分区
<回车> --默认分区编号
<回车> --默认起始扇区位置。
<回车> --默认结束扇区位置。
w --写入分区表
这样就把整个磁盘分成了一个区。
再看一下现有磁盘情况：
# fdisk -l
已经多出了一个新分区：
Device Boot Start End Blocks Id System
/dev/sdb1 2048 6291455 3144704 83 Linux
将新分区用于扩展/root
先看一下卷分组：
# vgdisplay -v
Finding all volume groups
Finding volume group "centos"
--- Volume group ---
VG Name centos
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 6
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 5
Open LV 5
Max PV 0
Cur PV 1
Act PV 1
VG Size 19.90 GiB
PE Size 4.00 MiB
Total PE 5094
Alloc PE / Size 5093 / 19.89 GiB
Free PE / Size 1 / 4.00 MiB
VG UUID vtJL08-7Jxi-5IqK-3fUg-Pben-682a-wiv2GL
--- Logical volume ---
LV Path /dev/centos/root
LV Name root
VG Name centos
LV UUID ZWTgoT-AMWs-g54v-dZA1-NQUj-mqGa-8tmr4U
LV Write Access read/write
LV Creation host, time localhost, 2016-07-03 21:59:31 -0400
LV Status available
# open 1
LV Size 1000.00 MiB
Current LE 250
Segments 1
Allocation inherit
Read ahead sectors auto
currently set to 256
Block device 253:2
...
...
...
--- Physical volumes ---
PV Name /dev/sda2
PV UUID fiVH1e-lwfi-63Lr-oIlK-GDZI-dcuZ-T04VlC
PV Status allocatable
Total PE / Free PE 5094 / 1
可以看到当前卷分组名为"centos"。
为之前新增的分区创建物理卷：
# pvcreate /dev/sdb1
提示是否擦除xfs签名，我选了y：
WARNING: xfs signature detected on /dev/sdb1 at offset 0. Wipe it? [y/n] y
Wiping xfs signature on /dev/sdb1.
Physical volume "/dev/sdb1" successfully created
查看结果：
# pvdisplay
已经看到新创建的3GiB大小的物理卷：
--- Physical volume ---
PV Name /dev/sda2
VG Name centos
PV Size 19.90 GiB / not usable 3.00 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 5094
Free PE 1
Allocated PE 5093
PV UUID fiVH1e-lwfi-63Lr-oIlK-GDZI-dcuZ-T04VlC
"/dev/sdb1" is a new physical volume of "3.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb1
VG Name
PV Size 3.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID VGXSAn-UiZ0-Fy40-eQxb-53xA-5hZM-3eGPg0
扩展卷分组,"centos"是vgdisplay命令查到的卷分组名：
# vgextend centos /dev/sdb1
提示成功扩展。
下面查看一下逻辑卷：
# lvdisplay
可以看到/dev/centos/root目前的LV Size是1000MiB。
下面扩展逻辑卷/dev/centos/root:
# lvextend -L +3G /dev/centos/root
注：+3G是我们新增加的分区大小。
扩展后，还要执行一步：
# xfs_growfs /dev/centos/root
将文件系统扩大。
完成。
因为安装CentOS用的xfs分区，所以使用命令xfs_growfs扩展文件系统大小。否则的话使用resize2fs命令。
查看结果：
# df -Th
/root已经扩充到4GiB：
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos-root xfs 4.0G 995M 3.1G 25% /
devtmpfs devtmpfs 915M 0 915M 0% /dev
tmpfs tmpfs 921M 0 921M 0% /dev/shm
tmpfs tmpfs 921M 8.4M 913M 1% /run
tmpfs tmpfs 921M 0 921M 0% /sys/fs/cgroup
/dev/mapper/centos-usr xfs 4.9G 1.6G 3.4G 33% /usr
/dev/mapper/centos-home xfs 9.8G 391M 9.4G 4% /home
/dev/mapper/centos-var xfs 2.4G 469M 1.9G 20% /var
/dev/sda1 xfs 97M 66M 31M 69% /boot