我们知道一个linux的启动过程，包括BIOS的加电自检POST，拷贝MBR的信息（启动BootLoader），加载内核，挂载根文件安系统这几大步，在嵌入式系统的移植方面我们也要自己动手制作内核映像，根文件系统等。今天境就带大家讲讲使用busybox制作嵌入式可以移植的根文件系统。
需要的材料：
1，busybox（busybox-1.14.2）
下载一个版本的busybox。下载地址。
busybox是主要用来提供一些bash shell命令的工具。
2，配置文件
重点配置文件是在境的上一篇文章提到的几个文件。linux启动过程中的几个重要文件的详解
3，设备文件(文中会教你如何添加)
4，必要的库文件（选用）
所以今天我要的做的就是由busybox等组成的rootfs。
制作过程：
第一步：编译busybox获得shell工具。
1，在用户主目录下建立一个用于我们实验的一个目录（～/exp/mkrootfs），并转至该目录；
@ubuntu:~$ mkdir -p ~/exp/mkrootfs
@ubuntu:~$ cd ~/exp/mkrootfs
2,将刚才的下载的busybox解压至此，并转至；
@ubuntu:~/exp/mkrootfs$ tar xvjf busybox-1.14.2.tar.bz2
@ubuntu:~/exp/mkrootfs$ cd busybox-1.14.2/
3，修改makefile文件来修改我们的arch和gcc编译工具；没有安装交叉编译工具的筒子请看快速安装ubuntu交叉编译工具。
@ubuntu:~/exp/mkrootfs$vim Makefile
修改164行：ROSS_COMPILE ?=/usr/bin/arm-linux-gnueabi-
修改190行：ARCH ?= arm
4，make menuconfig
@ubuntu:~/exp/mkrootfs$ make menuconfig
如果遇到像境这样的问题：请查看文章最后面。
5，优化我们的配置选项，在做make menuconfig之前最好，全屏打开你的terminal，这样才还显示类似编译内核一样的配置框，如下：
主要也是根据个人口味来选择优化配置，境选择如下：
Busybox Settings --->下的
General Configuration --->
Build Options --->
Debugging Options --->
Installation Options --->
Busybox Library Tuning --->
这几项都稍微看下，决定对你的有需要的就选山；比如补全命令，查看历史命令等有用的都选上。
6，编译安装我们的busybox
@ubuntu:~/exp/mkrootfs$make
@ubuntu:~/exp/mkrootfs$make install
这样我们可以得到我们的一个编译结果@ubuntu:~/exp/mkrootfs/busybox-1.14.2/_install$下的bin，sbin，linuxrc等。
第二步：完成第一步也就说明我们已经完成了一半任务，现在制作我们的根文件系统正式拉开帷幕：
1，建立一个根文件系统目录。可以利用下面这个脚本快速建立一些默认的文件系统框架。
@ubuntu:~/exp/rootfs$vim helprootfs.sh
#!/bin/sh
echo "------Create rootfs directons......"
mkdir rootfs
cd rootfs
echo "--------Create root,dev......"
mkdir root dev etc bin sbin mnt sys proc lib home tmp var usr
mkdir usr/sbin usr/bin usr/lib usr/modules
mkdir mnt/usb mnt/nfs mnt/etc mnt/etc/init.d
mkdir lib/modules
chmod 1777 tmp
cd ..
echo "-------make direction done---------" |
保存退出。
更改可执行权限
@ubuntu:~/exp$ chmod +x helprootfs.sh
@ubuntu:~/exp$ ./helprootfs.sh
------Create rootfs directons......
--------Create root,dev......
-------make direction done---------
并将刚才我们编译的busybox生成的_install目录下的文件拷贝至此：
@ubuntu:~/exp/rootfs$ cp ../mkrootfs/busybox-1.14.2/_install/* -a ./
这样就建好了一个根文件系统的大致框架。
2、创建设备文件
mdev 是通过 init 进程来启动的，在使用 mdev 构造 /dev 目录之前，init 至少要用到设备文件/dev/console、 /dev/null ，所以需要事先建立这两个设备文件:
@ubuntu:~/exp/rootfs$ cd dev/
@ubuntu:~/exp/rootfs/dev$ sudo mknod -m 660 console c 204 64
@ubuntu:~/exp/rootfs/dev$ sudo mknod -m 660 null c 1 3
@ubuntu:~/exp/rootfs/dev$ ls -l
total 0
crw-rw---- 1 root root 204, 64 2011-04-04 10:16 console
crw-rw---- 1 root root 1, 3 2011-04-04 10:16 null
3，准备一些配置文件和系统启动时所需的文件，这些文件的作用可以查看：（看好所在的目录）
(1)在mnt/etc下添加mdev。conf；
@ubuntu:~/exp/rootfs/mnt/etc$ touch mdev.conf
(2)在rootfs下添加linurc，rootfs下不要busybox下的linuxrs；
@ubuntu:~/exp/rootfs$ vim linuxrc
将下面内容写进去：
#!/bin/sh
echo "Processing /linuxrc"
echo "mount /etc as ramfs"
/bin/mount -n -t ramfs ramfs /etc
/bin/cp -a /mnt/etc/* /etc
echo "re-create the /etc/mtab entries"
/bin/mount -f -t cramfs -o remount,ro /dev/bon/3 /
/bin/mount -f -t ramfs ramfs /etc
echo "start init"
exec /sbin/init |
(3)在mnt/etc/init.d下添加rcS；
@ubuntu:~/exp/rootfs$ cd mnt/etc/init.d/
@ubuntu:~/exp/rootfs/mnt/etc/init.d$ vim rcS
将下面内容写进去
#!/bin/sh
echo "Processing /etc/init.d/rcS"
echo "mount -a"
mount -a #mount上fstab文件中所有文件系统
exec /etc/rc.local |
(4)在mnt/etc下添加rc.local文件；
@ubuntu:~/exp/rootfs/mnt/etc$ vim rc.local
添加下面的内容：
#!/bin/sh
echo "Processing /etc/rc.local"
echo "get hostname"
/bin/hostname -F /etc/hostname
echo "Starting mdev"
echo /sbin/mdev > /proc/sys/kernel/hotplug
mdev -s
echo "ifconfig eth0 192.168.1.21"
ifconfig eth0 192.168.1.21
echo "**************************************************"
echo "* *"
echo "* Linux ubuntu 2.6.32-30-generic *"
echo "* *"
echo "* arm-linux-gnueabi-gcc 4.4.5 *"
echo "* *"
echo "* 2011-04-04 *"
echo "* *"
echo "**************************************************" |
(5)在mnt/etc下添加profile文件：
@ubuntu:~/exp/rootfs/mnt/etc$ vim profile
添加下面内容：
#/etc/profile
echo "Processing /etc/profile"
echo "set user path"
PATH=/bin:/sbin:/usr/bin:/usr/sbin
echo "set search library path"
LD_LIBRARY_PATH=/lib:/usr/lib
echo "set PS1"
HOSTNAME=`/bin/hostname`
PS1='\u@\h:\w\$ ' ＃设置命令提示符为ubuntu风格
export PATH LD_LIBRARY_PATH HOSTNAME PS1 |
(6)改变权限；
@ubuntu:~/exp/rootfs$ chmod 775 linuxrc mnt/etc/init.d/rcS mnt/etc/rc.local mnt/etc/profile
(7)在mnt/etc下添加inittab文件：
@ubuntu:~/exp/rootfs/mnt/etc$ vim inittab
添加下面内容：
#/etc/inittab
::sysinit:/etc/init.d/rcS
console::askfirst:-/bin/sh
::ctrlaltdel:/sbin/reboot
::shutdown:/bin/umount -a -r |
(8)在mnt/etc下添加fstab文件：
@ubuntu:~/exp/rootfs/mnt/etc$ vim fstab
添加下面内容：
#/etc/fstab: static file system information.
#<File system> <mount pt> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
sysfs /sys sysfs defaults 0 0
mdev /dev ramfs defaults 0 0
none /tmp ramfs defaults 0 0 |
(9)在/etc下添加passwd文件：
@ubuntu:~/exp/rootfs/etc$ vim passwd
添加下面内容：
#username:password:User ID:Group ID:comment:home directory:shell
root:x:0:0:root:/root:/bin/sh |
(10)lib库文件复制到rootfs/lib目录下（根据需要复制）此处暂且不写了。
第三步：生成CramFS文件系统镜像文件myrootfs.img
1，下载CramFS制作工具，地址
2，解压编译（位子随便，最好在有别于rootf这个目录）
@ubuntu:~/tools$ tar xvzf cramfs-1.1.tar.gz
@ubuntu:~/tools$ make
这样就生成了我们需要的工具拉，你可以将cramfsck和mkcramfs添加到你的bin下，也可以不。
3，最后一步制作我们的镜像；
@ubuntu:~/exp$ ~/tools/cramfs-1.1/mkcramfs rootfs/ myrootfs.img
Directory data: 6424 bytes
Everything: 572 kilobytes
Super block: 76 bytes
CRC: 1245ce56
warning: gids truncated to 8 bits (this may be a security concern)
4，goodluck！如果遇到你的CramFS没有办法make，可以在互联网上搜到解决方法，其他请跟贴。
make menuconfig时候出错处理
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HOSTCC scripts/basic/fixdep
HOSTCC scripts/basic/split-include
scripts/basic/split-include.c: In function ‘main’:
scripts/basic/split-include.c:133: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
HOSTCC scripts/basic/docproc
HOSTCC scripts/kconfig/conf.o
scripts/kconfig/conf.c: In function ‘conf_askvalue’:
scripts/kconfig/conf.c:104: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
scripts/kconfig/conf.c: In function ‘conf_choice’:
scripts/kconfig/conf.c:359: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
HOSTCC scripts/kconfig/kxgettext.o
HOSTCC scripts/kconfig/mconf.o
scripts/kconfig/mconf.c: In function ‘exec_conf’:
scripts/kconfig/mconf.c:470: warning: ignoring return value of ‘pipe’, declared with attribute warn_unused_result
scripts/kconfig/mconf.c: In function ‘show_textbox’:
scripts/kconfig/mconf.c:836: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result
HOSTCC scripts/kconfig/zconf.tab.o
HOSTLD scripts/kconfig/mconf
HOSTCC scripts/kconfig/lxdialog/checklist.o
In file included from scripts/kconfig/lxdialog/checklist.c:24:
scripts/kconfig/lxdialog/dialog.h:31:20: error: curses.h: 没有那个文件或目录
In file included from scripts/kconfig/lxdialog/checklist.c:24:
scripts/kconfig/lxdialog/dialog.h:128: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘use_colors’
scripts/kconfig/lxdialog/dialog.h:129: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘use_shadow’
scripts/kconfig/lxdialog/dialog.h:131: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘attributes’
scripts/kconfig/lxdialog/dialog.h:143: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/dialog.h:146: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/dialog.h:147: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/dialog.h:148: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/dialog.h:149: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/dialog.h:151: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/checklist.c:31: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/checklist.c:59: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/checklist.c:95: error: expected ‘)’ before ‘*’ token
scripts/kconfig/lxdialog/checklist.c: In function ‘dialog_checklist’:
scripts/kconfig/lxdialog/checklist.c:117: error: ‘WINDOW’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:117: error: (Each undeclared identifier is reported only once
scripts/kconfig/lxdialog/checklist.c:117: error: for each function it appears in.)
scripts/kconfig/lxdialog/checklist.c:117: error: ‘dialog’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:117: error: ‘list’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:117: warning: left-hand operand of comma expression has no effect
scripts/kconfig/lxdialog/checklist.c:121: warning: implicit declaration of function ‘endwin’
scripts/kconfig/lxdialog/checklist.c:122: warning: implicit declaration of function ‘fprintf’
scripts/kconfig/lxdialog/checklist.c:122: warning: incompatible implicit declaration of built-in function ‘fprintf’
scripts/kconfig/lxdialog/checklist.c:122: error: ‘stderr’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:140: error: ‘COLS’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:141: error: ‘LINES’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:143: warning: implicit declaration of function ‘draw_shadow’
scripts/kconfig/lxdialog/checklist.c:143: error: ‘stdscr’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:145: warning: implicit declaration of function ‘newwin’
scripts/kconfig/lxdialog/checklist.c:146: warning: implicit declaration of function ‘keypad’
scripts/kconfig/lxdialog/checklist.c:146: error: ‘TRUE’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:148: warning: implicit declaration of function ‘draw_box’
scripts/kconfig/lxdialog/checklist.c:148: error: ‘attributes’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:149: warning: implicit declaration of function ‘wattrset’
scripts/kconfig/lxdialog/checklist.c:150: warning: implicit declaration of function ‘mvwaddch’
scripts/kconfig/lxdialog/checklist.c:152: warning: implicit declaration of function ‘waddch’
scripts/kconfig/lxdialog/checklist.c:156: warning: implicit declaration of function ‘print_title’
scripts/kconfig/lxdialog/checklist.c:159: warning: implicit declaration of function ‘print_autowrap’
scripts/kconfig/lxdialog/checklist.c:166: warning: implicit declaration of function ‘subwin’
scripts/kconfig/lxdialog/checklist.c:190: warning: implicit declaration of function ‘print_item’
scripts/kconfig/lxdialog/checklist.c:194: warning: implicit declaration of function ‘print_arrows’
scripts/kconfig/lxdialog/checklist.c:197: warning: implicit declaration of function ‘print_buttons’
scripts/kconfig/lxdialog/checklist.c:199: warning: implicit declaration of function ‘wnoutrefresh’
scripts/kconfig/lxdialog/checklist.c:201: warning: implicit declaration of function ‘doupdate’
scripts/kconfig/lxdialog/checklist.c:204: warning: implicit declaration of function ‘wgetch’
scripts/kconfig/lxdialog/checklist.c:211: error: ‘KEY_UP’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:211: error: ‘KEY_DOWN’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:221: error: ‘FALSE’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:222: warning: implicit declaration of function ‘scrollok’
scripts/kconfig/lxdialog/checklist.c:223: warning: implicit declaration of function ‘wscrl’
scripts/kconfig/lxdialog/checklist.c:232: warning: implicit declaration of function ‘wrefresh’
scripts/kconfig/lxdialog/checklist.c:282: warning: incompatible implicit declaration of built-in function ‘fprintf’
scripts/kconfig/lxdialog/checklist.c:283: warning: implicit declaration of function ‘delwin’
scripts/kconfig/lxdialog/checklist.c:287: error: ‘KEY_LEFT’ undeclared (first use in this function)
scripts/kconfig/lxdialog/checklist.c:288: error: ‘KEY_RIGHT’ undeclared (first use in this function)
make[2]: *** [scripts/kconfig/lxdialog/checklist.o] 错误 1
make[1]: *** [menuconfig] 错误 2
make: *** [menuconfig] 错误 2
@ubuntu:~/exp/mkrootfs$
解决办法：ubuntu系统中缺少一个套件 ncurses devel ，把此套件安装下即可
@ubuntu:~/exp/mkrootfs$ sudo apt-get install libncurses5-dev
http://www.ourunix.org/post/63.html
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来源：https://www.cnblogs.com/cainiaoaixuexi/archive/2013/06/13/3133891.html
