构建基本的嵌入式Linux根文件系统

其实在去年8月份我做系统移植时就构建好了一个可以用的根文件系统，但是那时是跟着别人的《Linux全线移植文档》做的。有些东西我也不清楚，只是跟着做，做出来能用就了事了，没有深究其中的规范，以及文件系统中哪些要，哪些不要。

趁着今年过年的几天假期，我移植重新移植了U-Boot1.3.1和Linux2.6.24到S3C2410及S3C2440后，我想好好的看看有关文件系统构建方法和规范，整理整理构建根文件系统的文档。之后，我用了近一周的时间，慢慢研究《构建嵌入式Linux系统》这本书有关根文件系统的部分，以及一些网上的参考资料，不断地实验。构建好了一个精简的根文件系统，下面我只介绍构建的过程和方法，至于原理我给出以下参考资料，自己看吧。

1、《Linux系统移植》：一个经典的Linux移植文档，共有95页的PDF文档，内容十分详细，里面有根文件系统的创建，还多地方都有下载（有的网站称之为《Linux系统全线移植文档》等等），很值得参考。在这里感谢文档的作者们。

2、《构建嵌入式Linux系统》必看！里面对文件系统的构建讲的挺细。

3、《Filesystem Hierarchy Standard》Linux文件系统的标准规范。我只看到英文的。

其他再遇到不懂的就google，基本上都是Linux的相关知识，都是找得到的。

（1）创建根文件系统的基本目录结构。
我把这个过程做成了shell脚本(文件名为mkroot) ，很方便！

#! /bin/sh echo "creatint rootfs dir......" mkdir rootfs cd rootfs echo "making dir : bin dev etc lib proc sbin sys usr" mkdir bin dev etc lib proc sbin sys usr #必备的8个目录 mkdir usr/bin usr/lib usr/sbin lib/modules



# Don't use mknod ,unless you run this Script as root !
# mknod -m 600 dev/console c 5 1
# mknod -m 666 dev/null c 1 3
 

    echo "making dir : mnt tmp var"
    mkdir mnt tmp var
    chmod 1777 tmp
    mkdir mnt/etc mnt/jffs2 mnt/yaffs mnt/data mnt/temp
    mkdir var/lib var/lock var/log var/run var/tmp 
    chmod 1777 var/tmp
 
    echo "making dir : home root boot"
    mkdir home root boot
    echo "done"

在你想要建立根文件系统的地方，运行：

[tekkamanninja@Tekkaman-Ninja nfs]$ ./mkroot creatint rootfs dir...... making dir : bin dev etc lib proc sbin sys usr making dir : mnt tmp var making dir : home root boot done [tekkamanninja@Tekkaman-Ninja nfs]$ cd rootfs/dev/ [tekkamanninja@Tekkaman-Ninja dev]$ su 口令： [root@Tekkaman-Ninja dev]# mknod -m 600 console c 5 1;mknod -m 666 null c 1 3;exit exit [tekkamanninja@Tekkaman-Ninja dev]$

（2）配置、编译和安装Busybox-1.9.1

[tekkamanninja@Tekkaman-Ninja source]$ tar -xjvf busybox-1.9.1.tar.bz2

修改Makefile文件：

[tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ pwd /home/tekkamanninja/working/source/busybox-1.9.1 [tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ kwrite Makefile ......(第151-154行) #SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ / # -e s/arm.*/arm/ -e s/sa110/arm/ / # -e s/s390x/s390/ -e s/parisc64/parisc/ / # -e s/ppc.*/powerpc/ -e s/mips.*/mips/ ) ......(第174行附近) #ARCH ?= $(SUBARCH) #CROSS_COMPILE ?= ARCH = arm CROSS_COMPILE = /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/bin/arm-9tdmi-linux-gnu- [tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ make menuconfig

在原有的基础上修改如下：

Busybox Settings --->
Installation Options --->
[*] Don't use /usr

(/home/tekkamanninja/working/nfs/rootfs) BusyBox installation prefix

Busybox Library Tuning --->

[*] Support for /etc/networks

[*] Additional editing keys

[*] vi-style line editing commands

(15) History size

[*] History saving

[*] Tab completion

[*] Username completion

[*] Fancy shell prompts

Linux Module Utilities --->

[N] Support version 2.2.x to 2.4.x Linux kernels

Shells --->

--- Ash Shell Options 下的选项全选

[tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ make ...... LINK busybox_unstripped Trying libraries: crypt m Library crypt is needed Library m is needed Final link with: crypt m [tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ make install

我是动态编译所以查看一下需要的动态库

[tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/bin/arm-9tdmi-linux-gnu-readelf -d busybox Dynamic section at offset 0xac014 contains 22 entries: Tag Type Name/Value 0x00000001 (NEEDED) Shared library: [libcrypt.so.1] 0x00000001 (NEEDED) Shared library: [libm.so.6] 0x00000001 (NEEDED) Shared library: [libc.so.6] 0x0000000c (INIT) 0xc0f0 0x0000000d (FINI) 0x97608 0x00000004 (HASH) 0x80e8 0x00000005 (STRTAB) 0xa3c0 0x00000006 (SYMTAB) 0x8b30 0x0000000a (STRSZ) 3371 (bytes) 0x0000000b (SYMENT) 16 (bytes) 0x00000015 (DEBUG) 0x0 0x00000003 (PLTGOT) 0xbc0ec 0x00000002 (PLTRELSZ) 2976 (bytes) 0x00000014 (PLTREL) REL 0x00000017 (JMPREL) 0xb550 0x00000011 (REL) 0xb4e0 0x00000012 (RELSZ) 112 (bytes) 0x00000013 (RELENT) 8 (bytes) 0x6ffffffe (VERNEED) 0xb400 0x6fffffff (VERNEEDNUM) 3 0x6ffffff0 (VERSYM) 0xb0ec 0x00000000 (NULL) 0x0

（3）修改和创建必要的文件。

[tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ cp -a examples/bootfloppy/etc/* /home/tekkamanninja/working/nfs/rootfs/etc/

[tekkamanninja@Tekkaman-Ninja busybox-1.9.1]$ cd ../../nfs/rootfs/etc/

1、增加为SHELL导入全局变量的文件/etc/profile

[tekkamanninja@Tekkaman-Ninja etc]$ kwrite profile

# /etc/profile: system-wide .profile file for the Bourne shells echo

echo "Processing /etc/profile... " # no-op

# Set search library path echo "Set search library path in /etc/profile" export LD_LIBRARY_PATH=/lib:/usr/lib # Set user path echo "Set user path in /etc/profile" PATH=/bin:/sbin:/usr/bin:/usr/sbin export PATH # Set PS1 #注意：ash 除了SHELL变量外，支持/u、/h、/W、/$、/!、/n、/w 、/nnn（ASCII字符对应的八进制数） #以及/e[xx;xxm (彩色特效)等等！ #而且前面还要多加一个 '/'！

echo "Set PS1 in /etc/profile"


export PS1="//e[05;32m[$USER@//w//a]//$//e[00;34m"

 

echo "Done"

echo

2、增加初始化文件

[tekkamanninja@Tekkaman-Ninja etc]$ kwrite inittab

::sysinit:/etc/init.d/rcS ::respawn:-/bin/login ::restart:/sbin/init ::ctrlaltdel:/sbin/reboot ::shutdown:/bin/umount -a -r ::shutdown:/sbin/swapoff -a

[tekkamanninja@Tekkaman-Ninja etc]$ kwrite fstab

proc /proc proc defaults 0 0 none /tmp ramfs defaults 0 0 mdev /dev ramfs defaults 0 0 sysfs /sys sysfs defaults 0 0

3、增加初始化脚本

[tekkamanninja@Tekkaman-Ninja etc]$ kwrite init.d/rcS

#! /bin/sh echo "----------mount all" /bin/mount -a

echo "----------Starting mdev......" /bin/echo /sbin/mdev > /proc/sys/kernel/hotplug mdev -s

echo "*********************************************************" echo " Tekkaman Ninja 2440 Rootfs(nfs) 2008.2 " echo " Love Linux ! ! @@ Love Ke Ke ! ! " echo "********************************************************"

4、删除备份文件

[tekkamanninja@Tekkaman-Ninja etc]$ rm *~ init.d/*~

5、为mdev创建配置文件

[tekkamanninja@Tekkaman-Ninja etc]$ vi mdev.conf

创建一个mdev.conf文件，内容可有可无。

（4）为使用用户登录功能移植TinyLogin

1、下载

从http://tinylogin.busybox.net/ 下载tinylogin-snapshot.tar.bz2，并解压.

[tekkamanninja@Tekkaman-Ninja source]$ tar -xjvf tinylogin-snapshot.tar.bz2

2、修改tinyLogin的Makefile

[tekkamanninja@Tekkaman-Ninja source]$ cd tinylogin

[tekkamanninja@Tekkaman-Ninja tinylogin]$ kwrite Makefile

指明tinyLogin使用自己的算法来处理用户密码

USE_SYSTEM_PWD_GRP = false ...... CROSS =/home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/bin/arm-9tdmi-linux-gnu- CC = $(CROSS)gcc AR = $(CROSS)ar STRIPTOOL = $(CROSS)strip

3、编译并安装

[tekkamanninja@Tekkaman-Ninja tinylogin]$ make PREFIX=/home/tekkamanninja/working/nfs/rootfs install Aborting install -- You must be root, otherwise I can't.

make tinylogin be setuid root, which will cause it to fail.

make: *** [install] 错误 1

[tekkamanninja@Tekkaman-Ninja tinylogin]$su

口令：

[root@Tekkaman-Ninja tinylogin]# make PREFIX=/home/tekkamanninja/working/nfs/rootfs install

[root@Tekkaman-Ninja tinylogin]# exit

exit

我是动态编译所以查看一下需要的动态库

[tekkamanninja@Tekkaman-Ninja tinylogin]$ /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/bin/arm-9tdmi-linux-gnu-readelf -d tinylogin Dynamic section at offset 0x9670 contains 21 entries: Tag Type Name/Value 0x00000001 (NEEDED) Shared library: [libcrypt.so.1] 0x00000001 (NEEDED) Shared library: [libc.so.6] 0x0000000c (INIT) 0x9c40 0x0000000d (FINI) 0x10160

0x00000004 (HASH) 0x8128 0x00000005 (STRTAB) 0x9070 0x00000006 (SYMTAB) 0x85e0 0x0000000a (STRSZ) 1430 (bytes) 0x0000000b (SYMENT) 16 (bytes) 0x00000015 (DEBUG) 0x0 0x00000003 (PLTGOT) 0x19740 0x00000002 (PLTRELSZ) 1064 (bytes) 0x00000014 (PLTREL) REL 0x00000017 (JMPREL) 0x9818 0x00000011 (REL) 0x97c8

0x00000012 (RELSZ) 80 (bytes)

0x00000013 (RELENT) 8 (bytes) 0x6ffffffe (VERNEED) 0x9758 0x6fffffff (VERNEEDNUM) 2 0x6ffffff0 (VERSYM) 0x9606 0x00000000 (NULL) 0x0

创建创建帐号及密码文件:

[tekkamanninja@Tekkaman-Ninja tinylogin]$ cd ../../nfs/rootfs/etc/ [tekkamanninja@Tekkaman-Ninja etc]$ su 口令： [root@Tekkaman-Ninja etc]# cp /etc/passwd . ;cp /etc/shadow . ;cp /etc/group . [root@Tekkaman-Ninja etc]# kwrite passwd root:x:0:0:root:/root:/bin/sh [root@Tekkaman-Ninja etc]# kwrite group

root:x:0:root [root@Tekkaman-Ninja etc]# kwrite shadow root:$1$N8K8eEQe$.XkJo3xcsjOE6vo1jW9Nk/:13923:0:99999:7::: [root@Tekkaman-Ninja etc]# rm *~ rm：是否删除普通文件 “group~”? y rm：是否删除普通文件 “passwd~”? y rm：是否删除普通文件 “shadow~”? y [root@Tekkaman-Ninja etc]# exit exit [tekkamanninja@Tekkaman-Ninja etc]$

这 3个文件是从Host中拷贝过来的，只留下root帐号。

那么现在 root的登陆密码和Host的登陆口令一致了，可以登录后再修改以及创建新用户。( 若使用以上文件，则root密码为tekkaman)

拷贝必需的动态库文件

[tekkamanninja@Tekkaman-Ninja lib]$ cp -d /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/ld* . cp: 略过目录 “/home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/ldscripts” [tekkamanninja@Tekkaman-Ninja lib]$ cp /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/libc-2.3.2.so .;cp -d /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/libc.so.6 . [tekkamanninja@Tekkaman-Ninja lib]$ cp /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/libm-* . ;cp -d /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/libm.s* . [tekkamanninja@Tekkaman-Ninja lib]$ cp /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/libcrypt-* . ;cp -d /home/tekkamanninja/working/gcc4.1.1/gcc-4.1.1-glibc-2.3.2/arm-9tdmi-linux-gnu/arm-9tdmi-linux-gnu/lib/libcrypt.s* .

以上是最基本的文件。

一个最基本根文件系统构建完成！未压缩的文件系统总大小不到3M。

以下是启动信息:

U-Boot 1.3.1 (Feb 18 2008 - 16:04:40) DRAM: 64 MB Flash: 1 MB NAND: NAND flash probing at 0x4E000000 64 MB In: serial Out: serial Err: serial Hit any key to stop autoboot: 0 dm9000 i/o: 0x20000300, id: 0x90000a46 MAC: 08:08:08:08:12:27 operating at 100M full duplex mode File transfer via NFS from server 192.168.1.22; our IP address is 192.168.1.2 Filename '/home/tekkamanninja/working/nfs/zImage.img'. Load address: 0x30008000 Loading: ################################################################# ################################################################# ################################################################# ################################################################# ####################################################### done Bytes transferred = 1611092 (189554 hex) ## Booting image at 30008000 ... Image Name: tekkamanninja Created: 2008-02-19 0:48:31 UTC Image Type: ARM Linux Kernel Image (uncompressed) Data Size: 1611028 Bytes = 1.5 MB Load Address: 30008000 Entry Point: 30008040 Verifying Checksum ... OK XIP Kernel Image ... OK Starting kernel ... Uncompressing Linux........................................................................................................ done, booting the kernel. Linux version 2.6.24 (tekkamanninja@Tekkaman-Ninja) (gcc version 4.1.1) #4 Tue Feb 19 08:48:15 CST 2008 CPU: ARM920T [41129200] revision 0 (ARMv4T), cr=c0007177 Machine: Tekkaman2440 Memory policy: ECC disabled, Data cache writeback CPU S3C2440A (id 0x32440001) S3C244X: core 405.000 MHz, memory 101.250 MHz, peripheral 50.625 MHz S3C24XX Clocks, (c) 2004 Simtec Electronics CLOCK: Slow mode (1.500 MHz), fast, MPLL on, UPLL on CPU0: D VIVT write-back cache CPU0: I cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets CPU0: D cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256 Kernel command line: noinitrd root=/dev/nfs rw nfsroot=192.168.1.22:/home/tekkamanninja/working/nfs/rootfs ip=192.168.1.2:192.168.1.22::255.255.255.0 console=ttySAC0,115200 init=/linuxrc mem=64M irq: clearing pending ext status 00000200 irq: clearing subpending status 00000002 PID hash table entries: 256 (order: 8, 1024 bytes) timer tcon=00500000, tcnt a4ca, tcfg 00000200,00000000, usec 00001e57 Console: colour dummy device 80x30 console [ttySAC0] enabled Dentry cache hash table entries: 8192 (order: 3, 32768 bytes) Inode-cache hash table entries: 4096 (order: 2, 16384 bytes) Memory: 64MB = 64MB total Memory: 61440KB available (2980K code, 309K data, 120K init) Mount-cache hash table entries: 512 CPU: Testing write buffer coherency: ok net_namespace: 64 bytes NET: Registered protocol family 16 S3C2410 Power Management, (c) 2004 Simtec Electronics S3C2440: Initialising architecture S3C2440: IRQ Support S3C2440: Clock Support, DVS off S3C24XX DMA Driver, (c) 2003-2004,2006 Simtec Electronics DMA channel 0 at c4800000, irq 33 DMA channel 1 at c4800040, irq 34 DMA channel 2 at c4800080, irq 35 DMA channel 3 at c48000c0, irq 36 usbcore: registered new interface driver usbfs usbcore: registered new interface driver hub usbcore: registered new device driver usb NET: Registered protocol family 2 IP route cache hash table entries: 1024 (order: 0, 4096 bytes) TCP established hash table entries: 2048 (order: 2, 16384 bytes) TCP bind hash table entries: 2048 (order: 1, 8192 bytes) TCP: Hash tables configured (established 2048 bind 2048) TCP reno registered NetWinder Floating Point Emulator V0.97 (double precision) JFFS2 version 2.2. (NAND) © 2001-2006 Red Hat, Inc. fuse init (API version 7.9) yaffs Feb 15 2008 10:10:34 Installing. io scheduler noop registered io scheduler anticipatory registered (default) io scheduler deadline registered io scheduler cfq registered Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled s3c2440-uart.0: s3c2410_serial0 at MMIO 0x50000000 (irq = 70) is a S3C2440 s3c2440-uart.1: s3c2410_serial1 at MMIO 0x50004000 (irq = 73) is a S3C2440 s3c2440-uart.2: s3c2410_serial2 at MMIO 0x50008000 (irq = 76) is a S3C2440 RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize loop: module loaded usbcore: registered new interface driver ub dm9000 Ethernet Driver eth0: dm9000 at f6100300,f6100304 IRQ 51 MAC: 08:08:08:08:12:27 Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx S3C24XX NAND Driver, (c) 2004 Simtec Electronics s3c2440-nand s3c2440-nand: Tacls=1, 9ns Twrph0=4 39ns, Twrph1=1 9ns NAND device: Manufacturer ID: 0xec, Chip ID: 0x76 (Samsung NAND 64MiB 3,3V 8-bit) Scanning device for bad blocks Bad eraseblock 3579 at 0x037ec000 Creating 7 MTD partitions on "NAND 64MiB 3,3V 8-bit": 0x00000000-0x00030000 : "U-Boot-1.3.1" 0x00030000-0x00040000 : "U-Boot-1.3.1 Parameter" 0x00040000-0x00500000 : "Linux2.6.24 Kernel(JFFS2)" 0x00500000-0x00a00000 : "Root(cramfs)" 0x00a00000-0x00f00000 : "Root(JFFS2)" 0x00f00000-0x01400000 : "Root(YAFFS)" 0x01400000-0x04000000 : "DATA" s3c2410-ohci s3c2410-ohci: S3C24XX OHCI s3c2410-ohci s3c2410-ohci: new USB bus registered, assigned bus number 1 s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000 usb usb1: configuration #1 chosen from 1 choice hub 1-0:1.0: USB hub found hub 1-0:1.0: 2 ports detected usb usb1: Product: S3C24XX OHCI usb usb1: Manufacturer: Linux 2.6.24 ohci_hcd usb usb1: SerialNumber: s3c24xx usbcore: registered new interface driver libusual mice: PS/2 mouse device common for all mice S3C24XX RTC, (c) 2004,2006 Simtec Electronics s3c2410-rtc s3c2410-rtc: rtc disabled, re-enabling s3c2410-rtc s3c2410-rtc: rtc core: registered s3c as rtc0 s3c2440-i2c s3c2440-i2c: slave address 0x10 s3c2440-i2c s3c2440-i2c: bus frequency set to 98 KHz s3c2440-i2c s3c2440-i2c: i2c-0: S3C I2C adapter S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics s3c2410-wdt s3c2410-wdt: watchdog inactive, reset disabled, irq enabled TCP cubic registered NET: Registered protocol family 1 RPC: Registered udp transport module. RPC: Registered tcp transport module. s3c2410-rtc s3c2410-rtc: setting system clock to 2008-02-20 16:01:20 UTC (1203523280) eth0: link down IP-Config: Complete: device=eth0, addr=192.168.1.2, mask=255.255.255.0, gw=255.255.255.255, host=192.168.1.2, domain=, nis-domain=(none), bootserver=192.168.1.22, rootserver=192.168.1.22, rootpath= Looking up port of RPC 100003/2 on 192.168.1.22 eth0: link up, 100Mbps, full-duplex, lpa 0x45E1 Looking up port of RPC 100005/1 on 192.168.1.22 VFS: Mounted root (nfs filesystem). Freeing init memory: 120K init started: BusyBox v1.9.1 (2008-02-20 14:54:41 CST) starting pid 781, tty '': '/etc/init.d/rcS' ----------mount all ----------Starting mdev...... ********************************************************* Tekkaman Ninja 2440 Rootfs(nfs) 2008.2 Love Linux ! ! @@ Love Ke Ke ! ! ******************************************************** starting pid 785, tty '': '/bin/login' 192.168.1.2 login: root Password: login[785]: root login on `console


 

Processing /etc/profile...

Set search library path in /etc/profile

Set user path in /etc/profile

Set PS1 in /etc/profile

Done

 

[root@/root]#

以上我使用nfs挂载的，后面我会介绍如何挂载jffs2、cramfs以及yaffs文件系统，有了这个基本的文件系统以后，其他就好办了！以下是这个文件系统，编译器是gcc4.1.2（制作编译器所用内核为2.6.24）。

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构建基本的嵌入式Linux根文件系统

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