yum -y install xfsdump

xfsdump -f /home.xfsdump /home

•  -> home
•  -> home

# 卸载 home
umount /home

# 如果提示
umount: /home: target is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))

# 解决方法
umount -l /home

# 将 home逻辑卷 缩减至 20GB
lvreduce -L 20G /dev/mapper/vg-home

# 增加 root 逻辑卷的容量
lvextend -l +100%FREE /dev/mapper/vg-root

xfs_growfs /dev/mapper/vg-root

# 格式化
mkfs.xfs -f /dev/mapper/vg-home

# 挂载
mount /home

# 还原
xfsrestore -f /home.xfsdump /home