方法原理：
１、centos6.2的dvd文件非常大，超过4G，fat32文件系统不支持4G以上文件；而用于引导linux的文件系统恰恰就是fat32格式。
２、 将u盘分成两个区，一个用于启动linux，为fat32文件系统；一个用于存放安装文件，为ext4文件系统。
过程步骤：
１、U盘参数：16G,/dev/sdb,默认已有分区为/dev/sdb4
2、删除原有分区
对U盘进行分区：第一个分区为FAT32，引导计算机进行系统安装，第二个分区为EXT4,存放我们的系统ISO文件。
以下过程命令：
[root@localhost ~]# 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
# 删除分区
Selected partition 4
Command (m for help): p
Disk /dev/sdb: 15.5 GB, 15479597056 bytes
255 heads, 63 sectors/track, 1881 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: 0xcad4ebea
Device Boot Start End Blocks Id System
Command (m for help): n
#新建分区
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
#
First cylinder (1-1881, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-1881, default 1881): +250M
#设置分区１大小
Command (m for help): t
#更改分区类型
Selected partition 1
Hex code (type L to list codes): l
#查看支持的分区类型
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT-
4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx
5 Extended 42 SFS 86 NTFS volume set da Non-FS data
6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linux plaintext de Dell Utility
8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt
9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access
a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs
e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT
f W95 Ext'd (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/
10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b
11 Hidden FAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor
12 Compaq diagnost 61 SpeedStor a9 NetBSD f4 SpeedStor
14 Hidden FAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary
16 Hidden FAT16 64 Novell Netware af HFS / HFS+ fb VMware VMFS
17 Hidden HPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE
18 AST SmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto
1b Hidden W95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep
1c Hidden W95 FAT3 80 Old Minix be Solaris boot ff BBT
1e Hidden W95 FAT1
Hex code (type L to list codes): b
Changed system type of partition 1 to b (W95 FAT32)
Command (m for help): n
#新建分区
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (34-1881, default 34):
Using default value 34
Last cylinder, +cylinders or +size{K,M,G} (34-1881, default 1881):
Using default value 1881
Command (m for help): t
#更改分区类型
Partition number (1-4): 2
Hex code (type L to list codes): 83
#分区类型id
Command (m for help): p
Disk /dev/sdb: 15.5 GB, 15479597056 bytes
255 heads, 63 sectors/track, 1881 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: 0xcad4ebea
Device Boot Start End Blocks Id System
/dev/sdb1 1 33 265041 b W95 FAT32
/dev/sdb2 34 1881 14844060 83 Linux
Command (m for help): a
#调整硬盘的启动分区
Partition number (1-4): 1
Command (m for help): p
Disk /dev/sdb: 15.5 GB, 15479597056 bytes
255 heads, 63 sectors/track, 1881 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: 0xcad4ebea
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 33 265041 b W95 FAT32
/dev/sdb2 34 1881 14844060 83 Linux
Command (m for help): w
#写入硬盘分区表
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)
WARNING: If you have created or modified any DOS 6.x
partitions, please see the fdisk manual page for additional
information.
Syncing disks.
[root@localhost ~]#
3、格式化U盘的两个分区
命名第一个分区卷名为boot，FAT32格式
第二个卷名为data，ext4格式,这个卷名大家随便起，各人习惯而已。
4、挂载boot分区和data分区到/mnt目录下
5、拷贝CentOS6.4第一张光盘CentOS-6.4-x86_64-bin-DVD1.iso中isolinux目录，到U盘boot分区中并
改名为syslinux目录，然后
重命名isolinux.cfg文件为syslinux.cfg。
6、如果系统中没有安装syslinux工具，yum install syslinux安装一下。
7、使用syslinux工具将U盘的/dev/sdb1分区制作成启动盘，拷贝光盘中image目录到boot分区。
8、将CentOS的两个DVDISO文件拷贝到U盘的data分区。文件比较大，使用rz无法上传，可以使用其它工具上传，如WinScp
9、Ｕ盘安装盘制作完成，下节使用虚拟机来进行验证。