上面已完成了u-boot,kernel現在我們來做一個根檔案系統

用busybox製作根檔案系統

1.下載Busybox,

官方下載地址:https://busybox.net/downloads/ sudo mkdir root_system 將下載後的檔案放入/qemu_arm/root_system中

2.解壓

[email protected]:/qemu_arm/root_system$ tar xjf busybox-1.26.2.tar.bz2 

3.編譯

make clean make menuconfig 在”Busybox Settings ---> Build Options --->“ 關閉“Build BusyBox as a static binary。
開啟”Build shared libbusybox“。
關閉”Produce a binary for each applet“與”Produce additional busybox binary“。
儲存退出
make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi-
make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- install
生成的檔案就放在_install目錄中了

4.檢視要用到的動態庫

方式1: [email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ arm-none-linux-gnueabi-readelf -d busybox| grep NEEDED
 0x00000001 (NEEDED)                     Shared library: [libm.so.6]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]
[email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ 
方式2:

[email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ arm-none-linux-gnueabi-objdump -x busybox| grep NEEDED
  NEEDED               libm.so.6
  NEEDED               libc.so.6
[email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ 
方式3: [email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ strings busybox | grep lib
/lib/ld-linux.so.3
libm.so.6
libc.so.6
__libc_start_main
/lib/modules
/var/lib/misc/udhcpd.leases
/lib/firmware
/var/lib/dpkg/info/%s.%s
/var/lib/dpkg/status
/var/lib/dpkg/status.udeb
/var/lib/dpkg/status.udeb.bak
shlibs

[email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ 
方式4: ldd busybox
顯示:not a dynamic executable     //不知為什麼 ,原因有待查詢 //-------------應該顯示為下面的提示才是正確的----------------- linux-gate.so.1 =>  (0xb775d000)
        libm.so.6 => /lib/i386-linux-gnu/libm.so.6 (0xb76ea000)
        libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7530000)
        /lib/ld-linux.so.2 (0x800ab000)
//--------------這說明 linux.so.2的庫還是存在依賴關係-------------

5.將編譯後的檔案拷到一個資料夾(rootfs)中:

 sudo mkdir rootfs
sudo chmod 777 rootfs/
sudo cp busybox-1.26.2/_install/* -r rootfs/
6.將busybox-1.26.2/examples/bootfloppy下的etc資料夾拷到rootfs資料夾中 [email protected]:/qemu_arm/root_system/rootfs$ sudo mkdir etc
[email protected]:/qemu_arm/root_system/rootfs$ sudo chmod 777 etc
[email protected]:/qemu_arm/root_system/rootfs$ sudo cp -r /qemu_arm/root_system/busybox-1.26.2/examples/bootfloppy/etc/* etc/

6.拷貝連結檔案

查詢libm.so.6檔案位置  [email protected]:/qemu_arm/root_system/rootfs$ arm-none-linux-gnueabi-readelf -d bin/busybox | grep NEEDED
 0x00000001 (NEEDED)                     Shared library: [libm.so.6]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]
[email protected]:/qemu_arm/root_system/rootfs$ locate libm.so.6 //查詢在哪裡
/arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/armv4t/lib/libm.so.6
/arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/lib/libm.so.6   //我們拷這個檔案
/arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/thumb2/lib/libm.so.6

/lib/i386-linux-gnu/libm.so.6

[email protected]:/qemu_arm/root_system/rootfs$  查詢libc.so.6檔案位置
[email protected]:/qemu_arm/root_system/rootfs$ locate libc.so.6
/arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/armv4t/lib/libc.so.6
/arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/lib/libc.so.6  //我們拷這個庫檔案
/arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/thumb2/lib/libc.so.6
/lib/i386-linux-gnu/libc.so.6

[email protected]:/qemu_arm/root_system/rootfs$ 
[email protected]:/qemu_arm/root_system/rootfs$ sudo mkdir lib
[email protected]:/qemu_arm/root_system/rootfs$ sudo chmod 777 lib

[email protected]:/qemu_arm/root_system/rootfs$ cp /arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/lib/lib*.so.6 lib   //檔案庫沒拷全,啟動時會提示 Kernel panic - not syncing: No working init found. 

[email protected]:/qemu_arm/root_system/rootfs$ cp /arm-none-linux-gnueabi/arm-2014.05/arm-none-linux-gnueabi/libc/lib/*.so*  lib

7.建立4個tty端終裝置

[email protected]:/qemu_arm/root_system/rootfs$ sudo mkdir dev
[email protected]:/qemu_arm/root_system/rootfs$ sudo mknod dev/tty1 c 4 1
[email protected]:/qemu_arm/root_system/rootfs$ sudo mknod dev/tty2 c 4 2
[email protected]:/qemu_arm/root_system/rootfs$ sudo mknod dev/tty3 c 4 3
[email protected]:/qemu_arm/root_system/rootfs$ sudo mknod dev/tty4 c 4 4

8.製作根檔案系統映象

1. 生成32M大小的映象

 busybox-1.26.2  busybox-1.26.2.tar.bz2  rootfs
[email protected]:/qemu_arm/root_system$ dd if=/dev/zero of=a9rootfs.ext3 bs=1M count=32
32+0 records in
32+0 records out
33554432 bytes (34 MB, 32 MiB) copied, 0.31139 s, 108 MB/s
[email protected]:/qemu_arm/root_system$ 

2. 格式化成ext3檔案系統

[email protected]:/qemu_arm/root_system$ mkfs.ext3 a9rootfs.ext3 

3.  將檔案拷貝到映象中

[email protected]:/qemu_arm/root_system$ sudo mkdir tmpfs
[email protected]:/qemu_arm/root_system$ sudo mount -t ext3 a9rootfs.ext3 tmpfs/ -o loop
[email protected]:/qemu_arm/root_system$ sudo cp -r rootfs/* tmpfs/
[email protected]:/qemu_arm/root_system$ sudo umount tmpfs
9.用Qemu測試生成的根檔案系統 qemu-system-arm -M vexpress-a9 -m 512M -kernel /qemu_arm/linux-kernel/linux-3.16.39/arch/arm/boot/zImage -nographic -append "root=/dev/mmcblk0  console=ttyAMA0" -sd /qemu_arm/root_system/a9rootfs.ext3
顯示一大堆資訊,最後出現提示如下:   #0: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 43
input: ImExPS/2 Generic Explorer Mouse as /devices/mb:kmi1/serio1/input/input2
kjournald starting.  Commit interval 5 seconds
EXT3-fs (mmcblk0): mounted filesystem with writeback data mode
VFS: Mounted root (ext3 filesystem) readonly on device 179:0.
Freeing unused kernel memory: 244K (805d6000 - 80613000)
random: nonblocking pool is initialized
mount: mounting proc on /proc failed: No such file or directory


Processing /etc/profile... Done


/ # 
說明核心已啟動並且掛接了檔案系統,此時已可以使用busybox的命令集了.

遇到的問題:

make clean make menuconfig make  make install 後生成的busybox不能用在ARM開發板中,因為沒有修改過MAKEFILE檔案所以就沒有指定用交叉編譯工具並且也不是arm的檔案格式 可使用file busybox檢視 [email protected]:/qemu_arm/root_system/busybox-1.26.2/_install/bin$ file busybox 
busybox: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.3, for GNU/Linux 2.6.16, stripped
注意紅色字ARM,這才是用於arm開發板的busybox 根檔案能掛接上,但不能執行,提示: Kernel panic - not syncing: No working init found. 
使用file命令檢視 [email protected]:/qemu_arm/root_system/rootfs$ file linuxrc 
linuxrc: symbolic link to bin/busybox
[email protected]:/qemu_arm/root_system/rootfs$ file /bin/busybox 
/bin/busybox: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, BuildID[sha1]=3009223865ed1ed7bfab5468767d7cd504d6ef49, stripped
還有要注間的就是連結庫的檔案要拷全,不能只拷libm.so.6和[libc.so.6兩個 另一個可能就在於上面提示的80386,可能在製作的過程中沒有指定ARCH=arm造成的

參考文件:

http://blog.csdn.net/f413933206/article/details/6534685