脚本完成一个10.8M，具有dropbear的嵌入式linux

本文内容是讲述，基于busybox构建嵌入式linux，并且结合Dropbrae打造提供ssh的10.8Mlinux。
国际惯例，废话不多说，步骤如下：
准备工作：
下载linux-2.6.34.1，下载地址：
http://www.kernel.org/pub/linux/kernel/v2.6/longterm/v2.6.34/linux-2.6.34.11.tar.bz2
下载busybox-1.16.1，下载地址：
http://www.busybox.net/downloads/binaries/1.16.1/busybox-i686
下载dropbear-2012.55，下载地址：
http://down.51cto.com/data/357545
注：由于busybox原生支持IDE硬盘，并不支持SCSI的硬盘，本人实验SCSI硬盘还未成功，将SCSI的驱动编译进内核仍然不行，希望博友们知道的不吝赐教，以下以IDE硬盘为基础。

由于需要编译内核，以及Busybox，不同的需要具有不同的选项，无法写进脚本，所以前面的步骤还是使用命令行完成：

1、添加IDE硬盘：

分区hda1作为boot分区
分区hda2作为根分区
分区hda3作为swap分区
并将其格式化为ext3，这里不在给出详细步骤。

2、创建挂载点：

#mkdir -pv /mnt/{boot,sysroot}
#mount /dev/hda1 /mnt/boot/
#mount /dev/hda2 /mnt/sysroot/

3、编译内核：

#tar xvf linux-2.6.34.1.tar.bz2 -C /usr/src/
#cd /usr/src
#ln  -sv  linux-2.6.34.1  linux
#cd linux
#cp /root/busybox/kernel-2.6.30.5-i686.cfg ./.config
#make menuconfig
注：kernel-2.6.30.5-i686.cfg为编译内核的选项模版，可以在附件中下载。
提示：为了实现后面的功能，请务必将文件系统中的ext3和网卡的驱动程序直接编译进内核；因为作者使用的是vmware Workstation虚拟机，所以，所需的网上驱动是pcnet32的，其它的均可按需要进行选择。

网卡驱动：pcnet32
Device Drivers  ---> Network device support  ---> Ethernet (10 or 100Mbit)  ---> EISA, VLB, PCI and on board controllers   AMD PCnet32 PCI support  
AMD 8111 (new PCI lance) support  

ext3文件系统：
File systems  ---> Ext3 journalling file system support  Default to 'data=ordered' in ext3

IDE硬盘驱动：
Device Drivers  --->  Block devices  --->   Very old hard disk (MFM/RLL/IDE) driver

SCSI硬盘驱动：
Device Drivers  --->  SCSI device support  --->  -*- SCSI device support
                    [*] SCSI target support
                    [*] SCSI generic support
                    [*] SCSI low-level drivers  --->
                                    [*]   BusLogic SCSI  support
                    [*] SCSI Device Handlers  --->   [*]   LSI RDAC Device Handler 
 
#make  SUBDIR=arch/
#cp arch/x86/boot/bzImage  /mnt/boot

4、安装busybox

#tar xvf busybox-1.16.1.tar.bz2 -C /usr/src
#cd /usr/src/busybox-1.16.1
#make menuconfig

Busybox Settings --> Build Options -->Build BusyBox as a static binary (no shared libs)
    Installation Options  --->  (./_install) BusyBox installation prefix，修改其值为/mnt/sysroot

Busybox Settings --> Busybox Library Tuning  --->     Username completion
                                                      Fancy shell prompts
                                                      Support for /etc/networks
                                                      Query cursor position from terminal



#make  install

安装后的文件均位于/mnt/sysroot目录中；但为了创建initrd，并实现让其启动以后将真正的文件系统切换至目标系统分区上的rootfs，您还需要复制一份刚安装在/mnt/sysroot下的busybox至另一个目录，以实现与真正的根文件系统分开制作。我们这里选择使用/mnt/temp目录；

#mkdir -pv /mnt/temp
#cp -r /mnt/sysroot/* /mnt/temp/

执行脚本buildlinux

#chmod +x buildlinux
#./buildlinux

提示：在脚本执行过程有两处和用户交互
1.要求用户为目标主机设置root用户的密码。
2.要求用户输入dropbear的源码包的完整路径。

由于初学，脚本可能写的不完善，只能接受.tar.bz2的dropbear源码包，还请博友们见谅。

脚本代码如下：

#!/bin/bash
# Name: buildlinux
# Description:
# Author: CZ
# Version: 1.1.0
# Datatime: 2012-03-26 12:25:25
# Usage: buildlinux

########################### 1 Make initrd ###########################
echo -e "[1] Make initrd....."
cd /mnt/temp

#[1]Build rootfs
mkdir -p proc sys etc/init.d tmp dev mnt/sysroot

#[2]Build equipment file
mknod dev/console c 5 1
mknod dev/null c 1 3

#[3]Make init for initrd
rm -rf linuxrc
cat > init << EOF
#!/bin/sh
mount -t proc proc /proc
mount -t sysfs sysfs /sys
mdev -s
mount -t ext3 /dev/hda2 /mnt/sysroot
exec switch_root /mnt/sysroot /init
EOF
chmod +x init

#[5]Make initrd
find . | cpio --quiet -H newc -o | gzip -9 -n > /mnt/boot/initrd.gz
if [ $? -eq 0 ];then
        echo -e "Make initrd  [\033[32mOK\033[0m]"
else
        echo -e "Make initrd  [\033[31mFail\033[0m]"
fi

########################### 2 Make reality filesystem ###########################
echo -e "[2] Make reality filesystem....."
cd /mnt/sysroot

#[1]Build rootfs
mkdir -p proc sys etc/init.d tmp dev/pts boot var/log boot home root
chmod -R 700 root/

#[2]Build equipment file
mknod dev/console c 5 1
mknod dev/null c 1 3

#[3]Build initialization system script file
cd /mnt/sysroot/etc/init.d
cat > rcS <
#!/bin/sh
echo -e "            Welcome to  \033[31mBuilt-in-Linux\033[0m                 "

echo -e "Remounting the root filesystem ..........[  \033[32mOK\033[0m  ]"
mount -t proc proc /proc
mount -t sysfs sysfs /sys
mount -o  remount,rw  /

echo -e "Creating the files of device ............[  \033[32mOK\033[0m  ]"
mdev -s

echo -e "Mounting the filesystem .................[  \033[32mOK\033[0m  ]"
mount -a
swapon -a

echo -e "Starting the log daemon .................[  \033[32mOK\033[0m  ]"
syslogd
klogd

echo -e "Configuring loopback interface ..........[  \033[32mOK\033[0m  ]"
ifconfig  lo  127.0.0.1/8
ifconfig eth0 172.16.4.6/16

# END
EOF
chmod +x rcS

#[4]Build inittab file
cd /mnt/sysroot
mv linuxrc init
cd /mnt/sysroot/etc
cat > inittab << EOF
::sysinit:/etc/init.d/rcS
::respawn:/sbin/getty 9600 tty1
::respawn:/sbin/getty 9600 tty2
::respawn:/sbin/getty 9600 tty3
::respawn:/sbin/getty 9600 tty4
::respawn:/sbin/getty 9600 tty5
::respawn:/sbin/getty 9600 tty6
::shutdown:/bin/umount -a -r
::ctrlaltdel:/sbin/reboot
EOF

#[5]Build fstab file
cat > fstab << EOF
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
devpts                  /dev/pts                devpts  mode=622        0 0
/dev/hda1               /boot                   ext3    defaults        1 2
/dev/hda2               /                       ext3    defaults        1 1
/dev/hda3               swap                    swap    defaults        0 0
EOF

#[6]Build syslog configure file
cat > syslog.conf << EOF
*.info          /var/log/messages
EOF
echo -e "Make reality filesystem  [\033[32mOK\033[0m]"

########################### 3 Install grub ###########################
echo -e "[3] Install grub....."
grub-install --root-directory=/mnt /dev/hda
NU31=`echo $?`

#[1]Build grub.conf file
cd /mnt/boot/grub
cat > grub.conf << EOF
default        0
timeout        3
color    light-green/black light-green/black
title    Busybox--Linux--Dropbear (2.6.34.1)
    root (hd0,0)
    kernel /bzImage ro root=/dev/hda2 quiet
    initrd /initrd.gz
EOF
NU32=`echo $?`
if [ $NU31 -eq 0 -a $NU32 -eq 0 ];then
        echo -e "Install grub  [\033[32mOK\033[0m]"
else
        echo -e "Install grub  [\033[31mFail\033[0m]"
fi
unset NU31 NU32

########################### 4 Build user files ###########################
echo -e "[4] Build user files....."
cd /mnt/sysroot

#[1]Build root passwd
head -1 /etc/passwd > /mnt/sysroot/etc/passwd
sed -i "s@/bin/bash@/bin/sh@" /mnt/sysroot/etc/passwd
chmod 400 /mnt/sysroot/etc/passwd

#[2]Build root group
head -1 /etc/group > /mnt/sysroot/etc/group

#[3]Build root shadow
read -p "Input a passwd for root: " PASS
while [ -z $PASS ];do
        read -p "Input a passwd for root" PASS
done
NUMBER=`echo $RANDOM$RANDOM`
PASSWD=`echo $PASS | openssl passwd -1 -salt $NUMBER -stdin`
echo "root:$PASSWD:15408:0:99999:7:::" > /mnt/sysroot/etc/shadow
chmod 400 /mnt/sysroot/etc/shadow
echo -e "Build user files  [\033[32mOK\033[0m]"
unset PASS NUMBER PASSWD

########################### 5 Build banner ###########################
echo -e "[5] Build banner....."
cd /mnt/sysroot/etc
cat > issue << EOF
                Welcome to Busybox-linux(grass51.blog.51cto.com)
                                Kernel \r
EOF
echo -e "Build banner  [\033[32mOK\033[0m]"

########################### 6 Set Hostname ###########################
echo -e "[6]Set Hostname config files"
mkdir /mnt/sysroot/etc/sysconfig
cd /mnt/sysroot/etc/sysconfig
echo > network << EOF
HOSTNAME=grass51.example.com
EOF
echo -e "Set Hostname config files  [\033[32mOK\033[0m]"

########################### 7 Build profile file ###########################
echo -e "[7] Build profile file....."
cd /mnt/sysroot/etc
cat > profile << EOF
export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
export PS1='[\u@\h \W]\$'
EOF
echo -e "Build profile file  [\033[32mOK\033[0m]"

########################### 8 OutPut PATH,Hostname ###########################
echo -e "[8] OutPut PATH,HOSTNAME....."
cd /mnt/sysroot/etc/init.d
cat >> rcS << EOF

[ -r /etc/sysconfig/network ] && source /etc/sysconfig/network
[ -z $HOSTNAME ] && /bin/hostname localhost || /bin/hostname $HOSTNAME

source /etc/profile
EOF
echo -e "OutPut PATH,HOSTNAME  [\033[32mOK\033[0m]"

########################### 9 Install dropbear ###########################
echo -e "[9] Install dropbear....."

read -p "Input the dropbear Package path[/tmp/dropbear-2012.55.tar.bz2]:" DROP_FILE
until [ -e $DROP_FILE ];do
        echo -e "$DROP_FILE not extis"
        read -p "Input a right Package path:" DROP_FILE
done
tar xf $DROP_FILE
FILEPATH=`echo ${DROP_FILE##*/}`
TARPATH=`echo $FILEPATH | sed 's@\(.*\).tar.bz2@\1@'`
cd $TARPATH

echo -e "\033[31m Begin configure\033[0m"
sleep 5
./configure
NU91=`echo $?`
if [ ! $NU91 -eq 0 ];then
        read -p "Sorry,configure error,Do you continue[N/y]" NU911
        case $NU911 in
                y|Y)
                        echo ""
                        ;;
                *)
                        exit
                        ;;
        esac
fi
make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp"
NU92=`echo $?`
if [ ! $NU92 -eq 0 ];then
        read -p "Sorry,make error,Do you continue[N/y]"  NU922
        case $NU922 in
                y|Y)
                        echo ""
                        ;;
                *)
                        exit
                        ;;
        esac
fi
make install
NU93=`echo $?`
if [ ! $NU93 -eq 0 ];then
        read -p "Sorry,make install error,Do you continue[N/y]"  NU933
        case $NU933 in
                y|Y)
                        echo ""
                        ;;
                *)
                        exit
                        ;;
        esac
fi
cp -a scp /usr/local/bin
cd ../
rm -rf $TARPATH


#[1]Build a explant lib file script
mkdir -p /mnt/sysroot/{usr/lib,lib}
for COMM in dropbear dropbearkey dropbearconvert dbclient scp;do
  TARGET=/mnt/sysroot

  COMMAND=`which $COMM | grep -o "/.*"`
  CMDPATH=${COMMAND%/*}

  [ -d $TARGET$CMDPATH ] || mkdir -p $TARGET$CMDPATH
  [ -e $TARGET$COMMAND ] || cp $COMMAND $TARGET$CMDPATH

  for LIBFILE in `ldd $COMMAND | grep -o "/.*lib[^[:space:]]*"`; do
        LIBPATH=${LIBFILE%/*}
        [ -d $TARGET$LIBPATH ] || mkdir -p $TARGET$LIBPATH
        [ -e $TARGET$LIBFILE ] || cp $LIBFILE $TARGET$LIBPATH
  done
done

unset COMM TARGET COMMAND CMDPATH LIBPATH
#[2]Build shells for Dropbear
cd /mnt/sysroot/etc
cat > shells << EOF
/bin/sh
/bin/ash
/bin/hush
EOF

#[3]Explant nsswitch
cat > nsswitch.conf << EOF
passwd:         files
shadow:         files
group:          files
hosts:          files dns
EOF

#[4]Explant nsswith libfiles
cd /usr/lib
cp -a libnss_compat.so libnss_db.so libnss_files.so libnss_dns.so libnssutil3.so

libnss3.so libnssckbi.so /mnt/sysroot/usr/lib/
cd /lib
cp -a libnss_compat* libnss_db* libnss_dns* libnss_files* /mnt/sysroot/lib/

#[5]Build private key
mkdir /mnt/sysroot/etc/dropbear
export PATH=$PATH:/usr/local/bin:/usr/local/sbin
dropbearkey -t rsa  -s 2048 -f /mnt/sysroot/etc/dropbear/dropbear_rsa_host_key
dropbearkey -t dss  -f /mnt/sysroot/etc/dropbear/dropbear_dss_host_key

if [ $NU91 -eq 0 -a $NU92 -eq 0 -a $NU93 -eq 0 ];then
        echo -e "Install dropbear  [\033[32mOK\033[0m]"
else
        echo -e "Install dropbear  [\033[31mFaile\033[0m]"
fi
unset NU91 NU911 NU92 NU922 NU93 NU933

 

到此一个10.8M的linux就制作好了，并且其中包含了大多数常用命令，而且还可以ssh远程连接！