實現DHCP自動獲取IP地址
前提：系統已經實現DNS（即使用ping www.baidu.com測試時能ping通）。
1． 在內核中添加以下選項：
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，后面子選項可不選，配置CONFIG_NETFILTER
說明：若沒選<* > Packet socket, [ * ] Network packet filtering (replaces ipchains) --->選項，在執行udhcpc命令時出現如下錯誤：
~ # 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中添加以下選項：
Networking Utilities --->
udhcp Server/Client --->
[] udhcp Server (udhcpd) //在此不作服務端，故不選。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沒編譯相應選項，也可從網上下載相應文件，用arm-linux交叉編譯得到udhcpd,udhcpc命令copy到usr/sbin下就可以了。
我從 網上 下的udhcp_0.9.8cvs20050303.orig.tar.gz文件
解壓后修改Makefile文件
在19行添加CROSS_COMPILE=arm-linux-
注釋12行的COMBINED_BINARY=1，否則不生成udhcpc命令。
3． 建相關配置文件
從busybox的examples/udhcp/下copy simple.script文件到開發板/usr/share/udhcpc/下，並重命名為default.script，udhcp_0.9.8cvs20050303.orig.tar.gz中也有這樣的文件。
[root@localhost root]# vi usr/share/udhcpc/default.script
#!/bin/sh
# udhcpc script edited by Tim Riker <Tim@Rikers.org>
[ -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． 重啟開發板，執行udhcpc就可自動獲取IP地址了，以下是執行udhcpc的輸出信息：
~ # 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． 如果是雙網卡必須用參數指明
例：udhcpc -i eth1