第一步：在虚拟机关闭状态下，点设置，硬盘，扩展，填入希望扩大到大小，比如256G。
第二步，启动虚拟机，打开一个terminal，切到root。
[root@myvm ~]# fdisk -l
Disk /dev/sda: 274.9 GB, 274877906944 bytes, 536870912 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: 0x00063057
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 616447 307200 83 Linux
/dev/sda2 616448 8744959 4064256 82 Linux swap / Solaris
/dev/sda3 8744960 167772159 79513600 83 Linux
从fdisk -l的结果看，可以识别到80G的硬盘变成了256G
第三步：确认磁盘格式为xfs，没有LVM。需要扩大的根分区是sda3
[root@myvm ~]# lsblk -f
NAME FSTYPE LABEL UUID MOUNTPOINT
sda
├─sda1 xfs 93794186-ed26-463a-b24d-7bf37d834a5c /boot
├─sda2 swap 69f9acc6-6695-4845-8d15-f63430d4c1de [SWAP]
└─sda3 xfs e0af8f45-b012-47d6-90d5-41391790f490 /
sr0
第四步：查找sda3的起始扇区：8744960
[root@myvm ~]# fdisk -l /dev/sda | grep "^/dev/sda3"
/dev/sda3 8744960 167772159 79513600 83 Linux
第五步：用fdisk /dev/sda，删除分区sda3，再重建sda3。起始扇区不变，结束扇区扩展。
需要注意的是：“起始扇区不变”是不丢数据的重要条件。
[root@myvm ~]# fdisk -l /dev/sda | grep "^/dev/sda3"
/dev/sda3 8744960 167772159 79513600 83 Linux
[root@myvm ~]# fdisk /dev/sda
Command (m for help): p
Disk /dev/sda: 274.9 GB, 274877906944 bytes, 536870912 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: 0x00063057
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 616447 307200 83 Linux
/dev/sda2 616448 8744959 4064256 82 Linux swap / Solaris
/dev/sda3 8744960 167772159 79513600 83 Linux
Command (m for help): d
Partition number (1-3, default 3): 3
Partition 3 is deleted
Command (m for help): n
Partition type:
p primary (2 primary, 0 extended, 2 free)
e extended Select (default p):p
Partition number (3,4, default 3): 3
First sector (8744960-536870911, default 8744960): 8744960
Last sector, +sectors or +size{K,M,G} (8744960-536870911, default 536870911):
Using default value 536870911
Partition 3 of type Linux and of size 251.9 GiB is set
Command (m for help):p
Disk /dev/sda: 274.9 GB, 274877906944 bytes, 536870912 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: 0x00063057
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 616447 307200 83 Linux
/dev/sda2 616448 8744959 4064256 82 Linux swap / Solaris
/dev/sda3 8744960 536870911 264062976 83 Linux
Command (m for help):w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8) Syncing disks.
依次输入以下命令（每行后按回车）：
| 输入 | 说明 |
|---|
p | 打印分区表，确认当前布局 |
d | 删除分区，然后输入 3 删除 sda3 |
n | 新建分区 |
3 | 分区号（保持为 3） |
8744960 | First sector（起始扇区）必须手动输入上面记下的数值，不要按回车默认！ |
| 直接按回车 | Last sector 使用默认（即最大空间） |
| 如果提示“检测到 xfs 签名” | 输入 N（保留原签名，不创建新文件系统） |
p | 再次打印，确认 Start=8744960，End 变为 536870911，Size 约为 256G |
w | 写入分区表并退出 |
第六步：刷新内核分区表，扩展xfs文件系统
[root@myvm ~]# partprobe /dev/sda
[root@myvm ~]# xfs_growfs /
meta-data=/dev/sda3 isize=512 agcount=4, agsize=4969600 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=0 spinodes=0 data = bsize=4096 blocks=19878400, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 ftype=1 log =internal bsize=4096 blocks=9706, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 data blocks changed from 19878400 to 66015744
第七步：验证结果
[root@myvm ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 2.9G 0 2.9G 0% /dev
tmpfs tmpfs 2.9G 0 2.9G 0% /dev/shm
tmpfs tmpfs 2.9G 13M 2.9G 1% /run
tmpfs tmpfs 2.9G 0 2.9G 0% /sys/fs/cgroup
/dev/sda3 xfs 252G 63G 190G 25% /
vmhgfs-fuse fuse.vmhgfs-fuse 454G 339G 115G 75% /mnt/hgfs
/dev/sda1 xfs 297M 138M 159M 47% /boot
tmpfs tmpfs 579M 20K 579M 1% /run/user/1000
🎉 扩容成功！
从 df -Th 输出可以看到，/dev/sda3 的大小已从原来的约 80GB 变为 252GB，可用空间从不足 20GB 增加到 190GB，整个操作过程 数据完整，文件系统无损。
📊 **最终状态 **
