一直以来对Hyper-V Linux虚拟主机的磁盘扩容困扰，今天将介绍如何利用 fdisk 和 resize2fs 进行数据磁盘扩容。
宿主机系统：Windwos Server 2012 R2 Hyper-V
虚拟主机：CentOS Linux release 7.4.1708 (Core)
平时接触Hyper-V较多，所以对磁盘扩容那是常有的事。Windwos磁盘扩容最简单，本文就不多介绍了。
今天我将以Centos虚拟主机进行演示，该小机分为两块磁盘（都是独立磁盘），一块是系统盘/dev/sda，另一块是数据库盘/dev/sdb，现在的需求是sdb需要在不影响数据的情况下从原来的30GB扩容为100GB。
[root@renwole-com ~]# fdisk -l
Disk /dev/sdb: 32.2 GB, 32212254720 bytes, 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x5f149419
Device Boot Start End Blocks Id System
/dev/sdb1 2048 62914559 31456256 83 Linux
Disk /dev/sda: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x00043041
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 20971519 9436160 8e Linux LVM
Disk /dev/mapper/cl-root: 8585 MB, 8585740288 bytes, 16769024 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk /dev/mapper/cl-swap: 1073 MB, 1073741824 bytes, 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
[root@renwole-com ~]# df -hT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/cl-root xfs 8.0G 950M 7.1G 12% /
devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 8.3M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sda1 xfs 1014M 138M 877M 14% /boot
tmpfs tmpfs 379M 0 379M 0% /run/user/0
/dev/sdb1 ext4 30G 60M 28G 1% /apps
注意：橙色部分 /dev/sdb1 分区大小是30GB，挂载的也是30GB。
删除 /etc/fstab 文件中以下开机磁盘自动挂载信息：
/dev/sdb1 /apps ext4 defaults 0 0
开始虚拟主机磁盘扩容
Hyper-V虚机操作：
打开Hyper-V 管理器，找到需要扩容的小机并关机，然后右击设置，点击需要扩容的磁盘，（一般是数据盘）编辑 – 默认下一步 – 选择扩展下一步，这一步骤需要注意，假设你原有磁盘为30G，那么你想扩展到100G，请填写100即可，点击下一步完成。然后启动虚拟主机。
[root@renwole-com ~]# fdisk -l
Disk /dev/sda: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x00043041
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 20971519 9436160 8e Linux LVM
Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x5f149419
Device Boot Start End Blocks Id System
/dev/sdb1 2048 62914559 31456256 83 Linux
Disk /dev/mapper/cl-root: 8585 MB, 8585740288 bytes, 16769024 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk /dev/mapper/cl-swap: 1073 MB, 1073741824 bytes, 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
sdb分区大小由原来的30GB扩展到100GB了，但分区sdb1并没有使用扩容的70GB空间，怎么办呢？
删除分区不同等删除数据，删除分区再重建：
[root@renwole-com ~]# fdisk /dev/sdb
The device presents a logical sector size that is smaller than
the physical sector size. Aligning to a physical sector (or optimal
I/O) size boundary is recommended, or performance may be impacted.
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): d # 删除sdb1分区
Selected partition 1
Partition 1 is deleted
Command (m for help): n # 新建分区
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): p
Partition number (1-4, default 1): 1 # 指定分区号
First sector (2048-209715199, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-209715199, default 209715199):
Using default value 209715199
Partition 1 of type Linux and of size 100 GiB is set
Command (m for help): w # 输入w保存
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
再次查看磁盘分区情况
[root@renwole-com ~]# fdisk -l
...
Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x5f149419
Device Boot Start End Blocks Id System
/dev/sdb1 2048 209715199 104856576 83 Linux
...
已经从原来的30G扩展成100G了，但现在还不能使用，需要进行如下操作才算真正扩容成功：
[root@renwole-com ~]# resize2fs -f /dev/sdb1
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/sdb1 to 26214144 (4k) blocks.
The filesystem on /dev/sdb1 is now 26214144 blocks long.
扩容成功。
[root@renwole-com ~]# mount /dev/sdb1 /apps/
[root@renwole-com ~]# df -hT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/cl-root xfs 8.0G 950M 7.1G 12% /
devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 8.3M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sda1 xfs 1014M 138M 877M 14% /boot
tmpfs tmpfs 379M 0 379M 0% /run/user/0
/dev/sdb1 ext4 99G 60M 94G 1% /apps
[root@renwole-com ~]# ls /apps/
web mysql
如上所示，Linux虚拟主机数据盘已经成功扩容，查看数据并无丢失。
另外再次将你的磁盘信息写入到 /etc/fstab 文件中，不然重启后磁盘还需要手动挂载。
注意：还是那句话，操作任何数据之前，一定要先备份，养成良好的习惯，以防止数据丢失。