从 CentOS7.0 开始，默认的文件系统变成了 XFS，比 CentOS6 默认的 EXT4 支持更大的文件系统容量。在这里，唯一需要注意的是，XFS 缩小容量的话会同时失去分区中的数据，所以在缩小分区容量之前，需要先做下数据备份。
目标
将 home 目录缩小至 5G，将剩下的容量全部加到根目录上。
[root@localhost ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos-root xfs 48G 1003M 47G 3% /
devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 8.8M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sda2 xfs 2.0G 145M 1.9G 8% /boot
/dev/mapper/centos-home xfs 50G 33M 50G 1% /home
tmpfs tmpfs 379M 0 379M 0% /run/user/0
备份
安装备份工具
yum -y install xfsdump
在根目录下备份为 home.xfsdump，需要保证根目录有足够的空间。
xfsdump -f /home.xfsdump /home
调整分区容量
缩小 home 容量，需要确保当前没有程序正在使用该目录中的数据。
umount /home
lvreduce -L 5G /dev/mapper/centos-home
输出
WARNING: Reducing active logical volume to 5.00 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 50.00 GiB (12800 extents) to 5.00 GiB (1280 extents).
Logical volume centos/home successfully resized.
扩容 root 根目录
lvextend -l +100%FREE /dev/mapper/centos-root
输出
Size of logical volume centos/root changed from <48.00 GiB (12287 extents) to <93.00 GiB (23807 extents).
Logical volume centos/root successfully resized.
磁盘扩容成功后需要同步到现有的文件系统（延展空间）
xfs_growfs /dev/centos/root
输出
meta-data=/dev/mapper/centos-root isize=512 agcount=4, agsize=3145472 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=12581888, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=6143, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 12581888 to 24378368
resize2fs 针对 ext2/ext3/ext4 文件系统的调整。xfs_growfs 针对 xfs 文件系统的调整。
恢复数据
无法直接挂载，缩小后的磁盘需要重新格式化才能使用。
mkfs.xfs -f /dev/mapper/centos-home
重新挂载
mount /dev/mapper/centos-home /home
将数据还原到 home 目录
xfsrestore -f /home.xfsdump /home
输出
xfsrestore: using file dump (drive_simple) strategy
xfsrestore: version 3.1.7 (dump format 3.0) - type ^C for status and control
xfsrestore: searching media for dump
xfsrestore: examining media file 0
xfsrestore: dump description:
xfsrestore: hostname: localhost.localdomain
xfsrestore: mount point: /home
xfsrestore: volume: /dev/mapper/centos-home
xfsrestore: session time: Mon Sep 11 01:22:34 2023
xfsrestore: level: 0
xfsrestore: session label: "home"
xfsrestore: media label: "home"
xfsrestore: file system id: 802b8a6d-5502-4585-8d67-5c994f827e73
xfsrestore: session id: c3dac766-698b-4f62-9b5d-a2b430682cef
xfsrestore: media id: e23b0de1-edf4-4b1f-b86a-a85c9e1c7f02
xfsrestore: using online session inventory
xfsrestore: searching media for directory dump
xfsrestore: reading directories
xfsrestore: 1 directories and 0 entries processed
xfsrestore: directory post-processing
xfsrestore: restore complete: 0 seconds elapsed
xfsrestore: Restore Summary:
xfsrestore: stream 0 /home.xfsdump OK (success)
xfsrestore: Restore Status: SUCCESS
最终效果
[root@localhost ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos-root xfs 93G 1.2G 92G 2% /
devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 8.8M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sda2 xfs 2.0G 145M 1.9G 8% /boot
tmpfs tmpfs 379M 0 379M 0% /run/user/0
/dev/mapper/centos-home xfs 5.0G 33M 5.0G 1% /home
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