服务器安装centos的时候，通常linux系统分区默认为3个分区，主分区最多4个，其他可根据自己的需要挂载。

/ 根分区，通常10-100G左右（根据总磁盘大小情况）
/boot 系统操作分区 （100-500MB 足矣）
/swap 虚拟内存暂存分区（通常是内存的2倍）

如果有剩下的磁盘就保留，后期再挂载。安装完系统后就开始格式化剩下的分区，并挂载指派出来。

1、首先查看未指派的分区名称，有的不一样，我的分别是/dev/sda和/dev/sdb，sda是系统分区，sdb是存储数据分区。

# 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: 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 /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

2、可以看到红色标注的是10G的数据磁盘，我们现在执行分区，代码如下：

# fdisk -S 56 /dev/sdb

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.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x52d681d6.

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.

Command (m for help):【输入n回车，添加新分区，如果需要更多，请输入m回车看帮助】

Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p):【输入p回车，P的意思是主分区】
Partition number (1-4, default 1):【输入数字1回车，分区数量】
First sector (2048-20971519, default 2048):【默认回车】
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519):【默认回车】
Using default value 20971519
Partition 1 of type Linux and of size 10 GiB is set

Command (m for help):【输入wq保存】

The partition table has been altered!

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

3、分区完成。输入fdisk -l查看信息

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: 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: 0x52d681d6

Device Boot Start End Blocks Id System
/dev/sdb1 2048 20971519 10484736 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

4、可以查看/dev/sdb1已经被默认分区，现在开始格式化此分区。

注意：以下有几种常用磁盘格式，如果你想格式化ext3格式,代码如下;

# mkfs.ext3 /dev/sdb1

格式化ext4格式，代码如下；

# mkfs.ext4 /dev/sdb1

我这里采用的是xfs磁盘格式；代码如下；

# mkfs.xfs -f /dev/sdb1

meta-data=/dev/sdb1 isize=512 agcount=4, agsize=655296 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=1 finobt=0, sparse=0
data = bsize=4096 blocks=2621184, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0

5、已经格式化成功。将磁盘挂载信息写入到系统配置文件中，不然开机不会自动挂载，代码如下；

# echo ‘/dev/sdb1 /www xfs defaults 0 0’ >> /etc/fstab
# mkdir /www //新建挂载目录
# mount -a //挂载磁盘
# df -h //查看挂载是否成功

Filesystem Size Used Avail Use% Mounted on
/dev/mapper/cl-root 8.0G 3.1G 5.0G 39% /
devtmpfs 906M 0 906M 0% /dev
tmpfs 916M 0 916M 0% /dev/shm
tmpfs 916M 8.3M 908M 1% /run
tmpfs 916M 0 916M 0% /sys/fs/cgroup
/dev/sda1 1014M 138M 877M 14% /boot
tmpfs 184M 0 184M 0% /run/user/0
/dev/sdb1 10G 33M 10G 1% /www

6、可以看到www目录已经挂载成功。

扩展阅读，fdisk -S 56 /dev/sdb的时候输入m有帮助信息，下面就列举说明：

a、toggle a bootable flag //切换一个可启动的标志
b、 edit bsd disklabel //编辑bsd disklabel
c、 toggle the dos compatibility flag //切换dos兼容性模式
d、 delete a partition //删除一个分区
g、 create a new empty GPT partition table //创建一个新的空GPT分区表
G 、create an IRIX (SGI) partition table //创建一个IRIX（SGI）分区表
l 、list known partition types //列出已知的分区类型
m、 print this menu //打印此菜单
n、 add a new partition //添加一个新的分区
o、 create a new empty DOS partition table //创建一个新的空DOS分区表
p、 print the partition table //打印分区表
q、 quit without saving changes //退出而不保存更改
s、 create a new empty Sun disklabel //创建一个新的空的Sun磁盘标签
t、 change a partition’s system id //更改分区的系统ID
u、 change display/entry units //更改显示/输入单位
v、 verify the partition table //验证分区表
w、 write table to disk and exit //将表写入磁盘保存并退出
x、extra functionality (experts only) //高级功能（仅限专家）