对于学习磁盘分区，通常学习的都是fdisk命令
当然，对于小于2TB的磁盘，我们基本上是使用fdisk命令进行分区
下面就简单介绍一下fdisk操作磁盘的基本命令和场景模拟

常用命令介绍
  fdisk -l 查看所有磁盘信息
  fdisk /dev/sdb  使用fdisk命令工具操作/dev/sdb磁盘
  m   显示所有的命令信息、用法
  p   显示分区信息
  q   退出
  w   保存分区信息，只有执行了w命令后才会把分区信息写入到磁盘
  d 1  删除磁盘的第一个分区

场景模拟

有一个1G的磁盘/dev/sdb

分区为一个主分区，一个扩展分区，大小都为200M

其中在扩展分区上面建立一个100M的逻辑分区 /dev/sdb5

格式化文件系统为 mkfs.ext4

实现开机自动挂载到目录 /backup3

1 使用fdisk命令工具操作磁盘/dev/sdb
   fdisk /dev/sdb
2 创建一个主分区
        Command (m for help): n 
 Command action
    e   extended
    p   primary partition (1-4)
 p
 Partition number (1-4): 1
 Using default value 1
 Last cylinder, +cylinders or +size{K,M,G} (1-130, default 130): +400M

 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: 0x0004a98a

    Device Boot      Start         End      Blocks   Id  System
 /dev/sdb1               1          52      417658+  83  Linux

3 创建一个扩展分区
 Command (m for help): n
 Command action
    e   extended
    p   primary partition (1-4)
 e
 Partition number (1-4): 2
 First cylinder (53-130, default 53):
 Using default value 53
 Last cylinder, +cylinders or +size{K,M,G} (53-130, default 130): +400M

 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: 0x0004a98a

    Device Boot      Start         End      Blocks   Id  System
 /dev/sdb1               1          52      417658+  83  Linux
 /dev/sdb2              53         104      417690    5  Extended

4 创建一个逻辑分区
 Command (m for help): n
 Command action
    l   logical (5 or over)
    p   primary partition (1-4)
 l
 First cylinder (53-104, default 53):
 Using default value 53
 Last cylinder, +cylinders or +size{K,M,G} (53-104, default 104): +100M

 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: 0x0004a98a

    Device Boot      Start         End      Blocks   Id  System
 /dev/sdb1               1          52      417658+  83  Linux
 /dev/sdb2              53         104      417690    5  Extended
 /dev/sdb5              53          66      112423+  83  Linux

5 保存
 Command (m for help): w
 The partition table has been altered!

 Calling ioctl() to re-read partition table.
 Syncing disks.

6 对磁盘进行分区
  [root@hsj2 ~]# mkfs.ext4 /dev/sdb1
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
104448 inodes, 417656 blocks
20882 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67633152
51 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 31 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

[root@hsj2 ~]# mkfs.ext4 /dev/sdb5
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
28112 inodes, 112420 blocks
5621 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67371008
14 block groups
8192 blocks per group, 8192 fragments per group
2008 inodes per group
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729

Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 31 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

ok，搞定