resize2fs 功能说明：调整ext2/ext3/ext4文件系统大小
resize2fs命令用于扩容或收缩未挂载的ext2/ext3/ext4文件系统。
在Linux2.6或更高版本的内核中，该命令还支持在线扩容已经挂载的文件系统，该命令常用来针对LVM扩容后的分区使用。

参数选项：
-p    打印完成任务的进度条
-f    强制执行操作


范例：动态修改分区大小的例子
假设是要对/dev/sdb上的分区进行操作，将/mnt/data1扩容。

[root@cs6 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
                       26G  834M   24G   4% /
tmpfs                 931M     0  931M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
/dev/sdb1             194M  1.8M  182M   1% /mnt/data1
/dev/sdb2             194M  1.8M  182M   1% /mnt/data2
[root@cs6 ~]# touch /mnt/data1/{1..5}.html
[root@cs6 ~]# touch /mnt/data2/{1..5}.html
 

提示：/dev/sdb是一块1GB的磁盘，现在分了两个主分区sdb1、sdb2，分别是200MB，剩余800MB未分区。现在需要把sdb2分区和sdb1分区合并，以实现对sdb1的扩容，
注意，此种情况不要在生产场景操作，仅作为演示用，生产场景一般是事先规划好不会出现扩容需求，非I/O密集应用可以采用LVM实现规范动态扩容。

以下是扩容实战步骤。

1）记录分区的柱面起始信息：

[root@cs6 ~]# fdisk -l /dev/sdb
 
Disk /dev/sdb: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1bc7d413
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          26      208813+  83  Linux
/dev/sdb2              27          52      208845   83  Linux


2）卸载分区：

[root@cs6 ~]# umount /mnt/data1
[root@cs6 ~]# umount /mnt/data2
 
[root@cs6 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
                       26G  834M   24G   4% /
tmpfs                 931M     0  931M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
 

3）重新分区：
 
[root@cs6 ~]# fdisk /dev/sdb
 
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').
 
Command (m for help): d
Partition number (1-4): 1
 
Command (m for help): d
Selected partition 2
 
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-130, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-130, default 130): 52
 
Command (m for help): p
 
Disk /dev/sdb: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1bc7d413
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          52      417658+  83  Linux
 
Command (m for help): w
The partition table has been altered!
 
Calling ioctl() to re-read partition table.
Syncing disks.
[root@cs6 ~]# partprobe /dev/sdb
[root@cs6 ~]# mount /dev/sdb1 /mnt/data1
[root@cs6 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
                       26G  834M   24G   4% /
tmpfs                 931M     0  931M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
/dev/sdb1             194M  1.8M  182M   1% /mnt/data1
 
 
[root@cs6 ~]# ls /mnt/data1
1.html  2.html  3.html  4.html  5.html  lost+found
[root@cs6 ~]# resize2fs /dev/sdb1    #<==在线调整磁盘大小，
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/sdb1 is mounted on /mnt/data1; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/sdb1 to 417656 (1k) blocks.
The filesystem on /dev/sdb1 is now 417656 blocks long.
 
[root@cs6 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
                       26G  834M   24G   4% /
tmpfs                 931M     0  931M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
/dev/sdb1             392M  2.3M  369M   1% /mnt/data1
[root@cs6 ~]# ls /mnt/data1
1.html  2.html  3.html  4.html  5.html  lost+found



但是数据还是只有sdb1里的了，sdb2的数据丢失了。
此种方法不适合生产场景扩容，比较规范方法是通过LVM逻辑卷管理进行扩容，扩容后也需要resize2fs进行最终实现扩容。