开发板网卡自动获取ip并设置网关

1. udhcpc命令
   udhcpc为busybox里的命令，可用于客户端自动获取ip并设置网关；

Usage: udhcpc [-fbnqvoCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]
        [-V VENDOR] [-x OPT:VAL]... [-O OPT]...

        -i,--interface IFACE    Interface to use (default eth0)
        -p,--pidfile FILE       Create pidfile
        -s,--script PROG        Run PROG at DHCP events (default /usr/share/udhcpc/default.script)
        -B,--broadcast          Request broadcast replies
        -t,--retries N          Send up to N discover packets
        -T,--timeout N          Pause between packets (default 3 seconds)
        -A,--tryagain N         Wait N seconds after failure (default 20)
        -f,--foreground         Run in foreground
        -b,--background         Background if lease is not obtained
        -n,--now                Exit if lease is not obtained
        -q,--quit               Exit after obtaining lease
        -R,--release            Release IP on exit
        -S,--syslog             Log to syslog too
        -a,--arping             Use arping to validate offered address
        -O,--request-option OPT Request option OPT from server (cumulative)
        -o,--no-default-options Don't request any options (unless -O is given)
        -r,--request IP         Request this IP address
        -x OPT:VAL              Include option OPT in sent packets (cumulative)
                                Examples of string, numeric, and hex byte opts:
                                -x hostname:bbox - option 12
                                -x lease:3600 - option 51 (lease time)
                                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)
        -F,--fqdn NAME          Ask server to update DNS mapping for NAME
        -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')
        -C,--clientid-none      Don't send MAC as client identifier
        -v 

#自动设置eth0网卡ip和网关
#-b 后台运行
#-s 指定配置脚本文件路径，默认路径为/usr/share/udhcpc/default.script
#-i 网卡接口
ifconfig eth0 up && udhcpc -b -s /etc/udhcpc.d/default.script -i eth0

2. default.script文件创建及内容添加
   创建文件

mkdir /etc/udhcpc.d
touch /etc/udhcpc.d/default.script

添加内容

#!/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 "$subnet" ] && NETMASK="netmask $subnet"

# return 0 if root is mounted on a network filesystem
root_is_nfs() {
        sed -n 's/^[^ ]* \([^ ]*\) \([^ ]*\) .*$/\1 \2/p' /proc/mounts |
        grep -q "^/ \(nfs\|smbfs\|ncp\|coda\)$"
}

have_bin_ip=0
if [ -x /sbin/ip ]; then
  have_bin_ip=1
  BROADCAST="broadcast +"
fi

[ -n "$broadcast" ] && BROADCAST="broadcast $broadcast"

case "$1" in
        deconfig)
                if [ -x /sbin/resolvconf ]; then
                        /sbin/resolvconf -d "${interface}.udhcpc"
                fi
                if ! root_is_nfs ; then
                        if [ $have_bin_ip -eq 1 ]; then
                                /sbin/ip addr flush dev $interface
                                /sbin/ip link set dev $interface up
                        else
                                /sbin/ifconfig $interface 0.0.0.0
                        fi
                fi
                ;;

        renew|bound)
                if [ $have_bin_ip -eq 1 ]; then
                        /sbin/ip addr add dev $interface local $ip/$mask $BROADCAST
                else
                        /sbin/ifconfig $interface $ip $BROADCAST $NETMASK
                fi

                if [ -n "$router" ] ; then
                        if ! root_is_nfs ; then
                                if [ $have_bin_ip -eq 1 ]; then
                                        while /sbin/ip route del default dev $interface 2>/dev/null ; do
                                                :
                                        done
                                else
                                        while /sbin/route del default gw 0.0.0.0 dev $interface 2>/dev/null ; do
                                                :
                                        done
                                fi
                        fi

                        metric=10
                        for i in $router ; do
                                if [ $have_bin_ip -eq 1 ]; then
                                        /sbin/ip route add default via $i metric $metric
                                else
                                        /sbin/route add default gw $i dev $interface metric $metric 2>/dev/null
                                fi
                                metric=$(($metric + 1))
                        done
                fi

                # Update resolver configuration file
                R=""
                [ -n "$domain" ] && R="domain $domain
"
                for i in $dns; do
                        echo "$0: Adding DNS $i"
                        R="${R}nameserver $i
"
                done

                if [ -x /sbin/resolvconf ]; then
                        echo -n "$R" | /sbin/resolvconf -a "${interface}.udhcpc"
                else
                        echo -n "$R" > "$RESOLV_CONF"
                fi
                ;;
esac

exit 0