转自 ：http://blog.csdn.net/zhangboyj/article/details/6154846
前提：系统已经实现DNS（即使用ping www.baidu.com测试时能ping通）。 1．  在内核中添加以下选项： Networking  --->    [*] Networking support         Networking options  --->            <* > Packet socket                 //添加.配置CONFIG_PACKET           [ * ]     IP: DHCP support         //添加           [ * ] Network packet filtering (replaces ipchains)  --->    //添加，后面子选项可不选，配置CONFIG_NETFILTER 说明：若没选<* > Packet socket, [ * ] Network packet filtering (replaces ipchains)  --->选项，在执行udhcpc命令时出现如下错误： ~ # udhcpc udhcpc (v0.9.9-pre) started udhcpc[208]: udhcpc (v0.9.9-pre) started   FATAL: couldn't listen on socket, Address family not supported by protocol udhcpc[208]: FATAL: couldn't listen on socket, Address family not supported by protocol 2．  Busybox中添加以下选项： Networking Utilities --->    udhcp Server/Client  --->         [] udhcp Server (udhcpd)       //在此不作服务端，故不选。生成udhcpd命令                                      [*] udhcp Client (udhcpc)       //生成udhcpc命令                                        [ ] Lease display utility (dumpleases)                                 [ ]   Log udhcp messages to syslog (instead of stdout)                 [ ]   Compile udhcp with noisy debugging messages 若busybox没编译相应选项，也可从网上下载相应文件，用arm-linux交叉编译得到udhcpd,udhcpc命令copy到usr/sbin下就可以了。 我从 网上  下的udhcp_0.9.8cvs20050303.orig.tar.gz文件 解压后修改Makefile文件 在19行添加CROSS_COMPILE=arm-linux-   注释12行的COMBINED_BINARY=1，否则不生成udhcpc命令。 3．建相关配置文件 从busybox的examples/udhcp/下copy  simple.script文件到开发板/usr/share/udhcpc/下，并重命名为default.script，udhcp_0.9.8cvs20050303.orig.tar.gz中也有这样的文件。 [root@localhost root]# vi usr/share/udhcpc/default.script #!/bin/sh   # udhcpc script edited by Tim Riker   [ -z "$1" ] && echo "Error: should be called from udhcpc" && exit 1   RESOLV_CONF="/etc/resolv.conf" [ -n "$broadcast" ] && BROADCAST="broadcast $broadcast" [ -n "$subnet" ] && NETMASK="netmask $subnet"   case "$1" in         deconfig)                 /sbin/ifconfig $interface 0.0.0.0                 ;;           renew|bound)                 /sbin/ifconfig $interface $ip $BROADCAST $NETMASK                   if [ -n "$router" ] ; then                         echo "deleting routers"                         while route del default gw 0.0.0.0 dev $interface ; do                                 :                         done                         for i in $router ; do                                 route add default gw $i dev $interface                         done                 fi                   echo -n > $RESOLV_CONF                 [ -n "$domain" ] && echo search $domain >> $RESOLV_CONF                 for i in $dns ; do                         echo adding dns $i                         echo nameserver $i >> $RESOLV_CONF                 done                 ;; esac   exit 0   4．重启开发板，执行udhcpc就可自动获取IP地址了，以下是执行udhcpc的输出信息：   ~ # udhcpc udhcpc (v0.9.9-pre) started udhcpc[228]: udhcpc (v0.9.9-pre) started   Sending discover... udhcpc[228]: Sending discover...   Sending select for 192.168.1.109... udhcpc[228]: Sending select for 192.168.1.109...   Lease of 192.168.1.109 obtained, lease time 86400 udhcpc[228]: Lease of 192.168.1.109 obtained, lease time 86400   deleting routers route: SIOC[ADD|DEL]RT: No such process adding dns 192.168.0.1 ~ # ping www.baidu.com PING www.a.shifen.com (220.181.38.4): 56 data bytes 64 bytes from 220.181.38.4: icmp_seq=0 ttl=52 time=1219.0 ms [1] + Stopped                    ping www.baidu.com   5．  如果是双网卡必须用参数指明 例：udhcpc  -i  eth1