情况：

1. home：500G
2. root：50G
3. root分区不够用

思路：把home分区的空间划一部分到root分区

# 设置home分区大小为200G，释放300G空间
$ lvreduce -L 200G /dev/centos/home

# 将空闲空间扩展到root分区
$ lvextend -l +100%FREE /dev/centos/root

# 使用XFS文件系统自带的命令集增加分区空间
$ xfs_growfs /dev/mapper/centos-root

实例

situation

挂载在根目录的分区 /dev/mapper/centos-root 爆满，占用100%

$ df -h
Filesystem        Size Used Avail Use% Mounted on
/dev/mapper/centos-root  50G  50G  19M 100% /
devtmpfs         32G   0  32G  0% /dev
tmpfs           32G   0  32G  0% /dev/shm
tmpfs           32G 2.5G  29G  8% /run
tmpfs           32G   0  32G  0% /sys/fs/cgroup
/dev/mapper/centos-home 476G  33M 476G  1% /home
/dev/sda1        497M 238M 259M 48% /boot
tmpfs          6.3G   0 6.3G  0% /run/user/0

analyze

挂载在根目录的分区空间太小，只有50G，而服务器 home 目录为非常用目录，挂在了近500G的空间。

思路：从 centos-home 分区划出300G空间到 centos-root 分区。

operation

1.查看各分区信息

$ lvdisplay
--- Logical volume ---
LV Path        /dev/centos/home
LV Name        home
VG Name        centos
LV UUID        1fAt1E-bQsa-1HXR-MCE2-5VZ1-xzBz-iI1SLv
LV Write Access    read/write
LV Creation host, time localhost, 2016-10-26 17:23:47 +0800
LV Status       available
# open         0
LV Size        475.70 GiB
Current LE       121778
Segments        1
Allocation       inherit
Read ahead sectors   auto
- currently set to   256
Block device      253:2

--- Logical volume ---
LV Path        /dev/centos/root
LV Name        root
VG Name        centos
LV UUID        lD64zY-yc3Z-SZaB-dAjK-03YM-2gM8-pfj4oo
LV Write Access    read/write
LV Creation host, time localhost, 2016-10-26 17:23:48 +0800
LV Status       available
# open         1
LV Size        50.00 GiB
Current LE       12800
Segments        1
Allocation       inherit
Read ahead sectors   auto
- currently set to   256
Block device      253:0

2.减少/home分区空间

# 释放 /dev/centos/home 分区 300G 的空间
# 命令设置 /dev/centos/home 分区 200G空间
$ lvreduce -L 200G /dev/centos/home
WARNING: Reducing active logical volume to 200.00 GiB.
 THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce centos/home? [y/n]: y
 Size of logical volume centos/home changed from 475.70 GiB (121778 extents) to 200.00 GiB (51200 extents).
 Logical volume centos/home successfully resized.

3.增加/root分区空间

$ lvextend -l +100%FREE /dev/centos/root
Size of logical volume centos/root changed from 50.06 GiB (12816 extents) to 325.76 GiB (83394 extents).
Logical volume centos/root successfully resized.

4.扩展XFS文件空间大小

$ xfs_growfs /dev/mapper/centos-root
meta-data=/dev/mapper/centos-root isize=256  agcount=4, agsize=3276800 blks
     =            sectsz=512  attr=2, projid32bit=1
     =            crc=0    finobt=0 spinodes=0
data   =            bsize=4096  blocks=13107200, imaxpct=25
     =            sunit=0   swidth=0 blks
naming  =version 2       bsize=4096  ascii-ci=0 ftype=0
log   =internal        bsize=4096  blocks=6400, version=2
     =            sectsz=512  sunit=0 blks, lazy-count=1
realtime =none          extsz=4096  blocks=0, rtextents=0
data blocks changed from 13107200 to 85395456