/*****************************************************************************
 *                      RPi 2B Raspbian SD卡内部架构
 * 声明：
 *     本文主要想了解RPi 2B Raspbian SD卡中文件存放方式。
 *
 *                                          2016-1-29 深圳 南山平山村 曾剑锋
 ****************************************************************************/

一、参考文章：
    1. RPi Advanced Setup
        http://elinux.org/RPi_Advanced_Setup
    2. Formatting the SD card via the mkcard.txt script
        http://downloads.angstrom-distribution.org/demo/beaglebone/mkcard.txt
    3. RPi cmdline.txt
        http://elinux.org/RPi_cmdline.txt

二、总结：
    1.  RPi 2B Raspbian SD被分区为2个分区(we want to create two partitions. One for the boot image, one for our distro.)：
        Device    Boot      Start         End      Blocks   Id  System
        /dev/sdc1   *           1          51      409626    c  W95 FAT32 (LBA)
        /dev/sdc2              52         245     1558305   83  Linux
    2. 文件系统类型：
        cat cmdline.txt
            ......
            rootfstype=ext4
            ......
    3. boot分区内容：
        zengjf@zengjf:/media/boot$ ls -al
        total 19892
        drwx------ 3 myzr myzr   16384 Jan  1  1970 .
        drwxr-xr-x 5 root root    4096 Jan 29 17:01 ..
        -rw-r--r-- 1 myzr myzr    9846 Nov 18 16:01 bcm2708-rpi-b.dtb
        -rw-r--r-- 1 myzr myzr   10125 Nov 18 16:01 bcm2708-rpi-b-plus.dtb
        -rw-r--r-- 1 myzr myzr    9850 Nov 18 16:01 bcm2708-rpi-cm.dtb
        -rw-r--r-- 1 myzr myzr   11113 Nov 18 16:01 bcm2709-rpi-2-b.dtb
        -rw-r--r-- 1 myzr myzr   17900 Nov 18 16:01 bootcode.bin
        -rw-r--r-- 1 myzr myzr     136 Nov 21 20:28 cmdline.txt
        -rw-r--r-- 1 myzr myzr    1635 Nov 21 20:28 config.txt
        -rw-r--r-- 1 myzr myzr   18693 Aug 21 16:04 COPYING.linux
        -rw-r--r-- 1 myzr myzr    2472 Nov 18 16:01 fixup_cd.dat
        -rw-r--r-- 1 myzr myzr    6446 Nov 18 16:01 fixup.dat
        -rw-r--r-- 1 myzr myzr    9684 Nov 18 16:01 fixup_db.dat
        -rw-r--r-- 1 myzr myzr    9684 Nov 18 16:01 fixup_x.dat
        -rw-r--r-- 1 myzr myzr     110 Nov 21 21:35 issue.txt
        -rw-r--r-- 1 myzr myzr 4035396 Nov 18 16:01 kernel7.img
        -rw-r--r-- 1 myzr myzr 4059512 Nov 18 16:01 kernel.img
        -rw-r--r-- 1 myzr myzr    1494 Nov 18 16:01 LICENCE.broadcom
        -rw-r--r-- 1 myzr myzr   18974 Nov 21 21:35 LICENSE.oracle
        drwx------ 2 myzr myzr    8192 Nov 21 20:32 overlays
        -rw-r--r-- 1 myzr myzr  604376 Nov 18 16:01 start_cd.elf
        -rw-r--r-- 1 myzr myzr 4856072 Nov 18 16:01 start_db.elf
        -rw-r--r-- 1 myzr myzr 2730232 Nov 18 16:01 start.elf
        -rw-r--r-- 1 myzr myzr 3811048 Nov 18 16:01 start_x.elf
    4. ext4文件系统内容：
        zengjf@zengjf:/media/ad6203a1-ec50-4f44-a1c0-e6c3dd4c9202$ ls -al
        total 96
        drwxr-xr-x  21 root root  4096 Nov 22 04:39 .
        drwxr-xr-x   5 root root  4096 Jan 29 17:01 ..
        drwxr-xr-x   2 root root  4096 Nov 22 04:48 bin
        drwxr-xr-x   3 root root  4096 Nov 22 04:32 boot
        drwxr-xr-x   4 root root  4096 Nov 22 02:51 dev
        drwxr-xr-x 108 root root  4096 Nov 22 05:36 etc
        drwxr-xr-x   3 root root  4096 Nov 22 04:32 home
        drwxr-xr-x  19 root root  4096 Nov 22 04:48 lib
        drwx------   2 root root 16384 Nov 22 03:39 lost+found
        drwxr-xr-x   2 root root  4096 Nov 22 02:50 media
        drwxr-xr-x   2 root root  4096 Nov 22 02:50 mnt
        drwxr-xr-x   6 root root  4096 Nov 22 05:29 opt
        drwxr-xr-x   2 root root  4096 Jan  7  2015 proc
        drwx------   2 root root  4096 Nov 22 02:50 root
        drwxr-xr-x   5 root root  4096 Nov 22 04:38 run
        drwxr-xr-x   2 root root  4096 Nov 22 04:48 sbin
        drwxr-xr-x   2 root root  4096 Nov 22 02:50 srv
        drwxr-xr-x   2 root root  4096 Apr 12  2015 sys
        drwxrwxrwt   9 root root  4096 Nov 22 05:36 tmp
        drwxr-xr-x  10 root root  4096 Nov 22 02:50 usr
        drwxr-xr-x  11 root root  4096 Nov 22 05:35 var