CentOS Linux如何无损调整分区大小（XFS文件系统）
系统环境: CentOS 7.2 64-bit情况：
/home：873GB
/：50GB
/ 分区不够用
思路：
把home分区的空间划一部分到root分区
操作：
1、通过df -h查看分区情况
# df -h
Filesystem SizeUsed Avail Use% Mounted on
/dev/mapper/cl-root 50G 31G 20G62% /
devtmpfs 7.8G 07.8G 0% /dev
tmpfs 7.8G 07.8G 0% /dev/shm
tmpfs 7.8G817M7.0G11% /run
tmpfs 7.8G 07.8G 0% /sys/fs/cgroup
/dev/mapper/cl-home 873G 31M 873G1% /home
/dev/sda2 1014M131M884M13% /boot
/dev/sda1 200M9.5M191M 5% /boot/efi
tmpfs 1.6G 01.6G 0% /run/user/0
2、lvdisplay 查看各分区的信息
# lvdisplay
--- Logical volume ---
LV Path /dev/cl/swap
LV Name swap
VG Name cl
LV UUID DDpjMZ-SFwL-IVud-cewL-yqeK-TFqe-tAS9b4
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2017-10-17 16:48:55 +0800
LV Status available
# open 2
LV Size 7.88 GiB
Current LE 2016
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
--- Logical volume ---
LV Path /dev/cl/home
LV Name home
VG Name cl
LV UUID 21q7cu-zJyg-R6W5-gpEt-ctb3-CqH7-TyoGOH
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2017-10-17 16:48:56 +0800
LV Status available
# open 1
LV Size 872.43 GiB
Current LE 223343
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:2
--- Logical volume ---
LV Path /dev/cl/root
LV Name root
VG Name cl
LV UUID paz3dp-GQ9T-VqAT-gPGT-Q2Go-tMro-zSpDLQ
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2017-10-17 16:48:59 +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
3、减少/dev/centos/home的空间
# 命令设置 /dev/centos/home 分区 50G空间
# lvreduce -L 50G /dev/cl/home
WARNING: Reducing active logical volume to 50.00 GiB.
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce cl/home? : y
Size of logical volume cl/home changed from 872.43 GiB (223343 extents) to 50.00 GiB (12800 extents).
Logical volume cl/home successfully resized.
4、增加/dev/centos/root的空间
# lvextend -l +100%FREE /dev/cl/root
Size of logical volume cl/root changed from 50.00 GiB (12800 extents) to 872.44 GiB (223344 extents).
Logical volume cl/root successfully resized.
5、扩展XFS文件空间大小
# xfs_growfs /dev/mapper/cl-root
meta-data=/dev/mapper/cl-root isize=512 agcount=4, agsize=3276800 blks
= sectsz=4096attr=2, projid32bit=1
= crc=1 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=1
log =internal bsize=4096 blocks=6400, version=2
= sectsz=4096sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 13107200 to 228704256
到此/dev/centos/root的扩展结束，不过还有一些后遗症，调整后的/dev/mapper/cl-home 显示的大小一直不正常，这样也会导致重启的时候无法根据/etc/fstab里面的规则挂载正确的/home，直接进入紧急模式（welcome to emergency mode），由于我们/home里面没有什么文件，所以我们用格式化的办法，进行了修复。
# mkfs.xfs /dev/mapper/cl-home
这样再卸载和挂载就没有问题了
# umount /home
# mount /home
至此整个的调整分区圆满结束。
留下一个小问题做思考，就是如果同时想保留/dev/mapper/centos-home里面的数据的话，如何无损调整分区？
http://bbs.cuwww.com/thread-17540-1-1.html
这里是EXT3/EXT4文件系统的分区调整方法 一直没有找到把调整小了的分区（/dev/mapper/centos-home）里面的数据完整保留下来的办法，谁有办法，请在下面留言。
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