空emmc flash的使用

这里主要记录fdisk命令的常用使用方法，如何对emmc做最基本的如分区，格式化等操作。

1、根据系统启动信息，查看emmc的基本信息
硬件上电启动，在内核的启动信息中找到了如下信息：

emmc在/dev下的设备文件为:mmcblk0, 使用ls名查看/dev目录下文件，确认mmcblk0设备文件存在；如果存在进行下一步fdisk操作。

2、使用fdisk对emmc进行分区
2.1、对emmc进行分区
# fdisk /dev/mmcblk0
Device contains neither a valid DOS partition table, nor Sun, SGI, OSF or GPT disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that the previous content
won't be recoverable.

The number of cylinders for this disk is set to 238592.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help):

2.2、使用m命令，获取fdisk使用帮助
Command (m for help): m
Command Action
a       toggle a bootable flag
b       edit bsd disklabel
c       toggle the dos compatibility flag
d       delete a partition
l       list known partition types
n       add a new partition
o       create a new empty DOS partition table
p       print the partition table
q       quit without saving changes