经过昨天的实践，终于搞定Ubuntu共享WiFi功能，而且不是Ad-hoc模式。从此“二奶”可以作为无线中继使用（这里指的是在Ubuntu系统下）。参考教程：
Ubuntu共享WiFi(AP)给Android/更新方法二 http://weibin.me/538

首先很重要的是，要确定无线网卡驱动是否支持master mode。如果不支持，就别想了。然后就可以按照教程安装并设置hostapd和dnsmasq。根据教程，写了个脚本，方便启动或关闭该功能。第一次写比较长的Shell脚本，所以该脚本还是不太完善，但基本可用。要注意，/etc/dnsmasq.conf还是要手动修改。脚本如下：

#!/bin/sh
# begin file: sharewifi
    
# Setup wireless AP, share the Internet from interface0 to interface1
# USAGE: sharewifi [ start | stop ] interface0 interface1
# EXAMPLE: sharewifi start wlan1 wlan0
    
help( )
{
    cat << HELP
    Setup wireless AP, share the Internet from interface0 to interface1
    USAGE: sharewifi [ help | start | stop ] interface0 interface1
    EXAMPLE: sharewifi start wlan1 wlan0
    HELP
    exit 0
}
    
start( )
{
    echo Starting share wifi ......
    echo Share Internet $port_in to $port_out
    
    # Configure iptable rules
    iptables -F
    iptables -t nat -A POSTROUTING -s 192.168.7.0/24 -o $port_in -j MASQUERADE
    iptables -A FORWARD -s 192.168.7.0/24 -o $port_in -j ACCEPT
    iptables -A FORWARD -d 192.168.7.0/24 -m conntrack --ctstate ESTABLISHED,RELATED -i $port_in -j ACCEPT
    
    # Log the message of route
    #iptables -A INPUT -m conntrack --ctstate NEW -p tcp --dport 80 -j LOG --log-prefix "NEW_HTTP_CONN: "
    
    # Save iptable rules
    sh -c "iptables-save > /etc/iptables.rules"
    
    # Configure hostapd
    hostapd_conf=/etc/hostapd/hostapd.conf
    [ -f $hostapd_conf ] && rm $hostapd_conf
    echo >> $hostapd_conf interface=$port_out
    echo >> $hostapd_conf driver=nl80211
    echo >> $hostapd_conf ssid=AO522-Tether
    echo >> $hostapd_conf channel=1
    echo >> $hostapd_conf hw_mode=g
    echo >> $hostapd_conf auth_algs=1
    echo >> $hostapd_conf wpa=3
    echo >> $hostapd_conf wpa_passphrase=1234567890
    echo >> $hostapd_conf wpa_key_mgmt=WPA-PSK
    echo >> $hostapd_conf wpa_pairwise=TKIP CCMP
    echo >> $hostapd_conf rsn_pairwise=CCMP
    chmod 755 $hostapd_conf
    
    # Configure /etc/dnsmasq.conf
    #interface=wlan0
    #bind-interfaces #这个是只监听wlan0，没有之会检测所有卡
    #except-interface=lo
    #dhcp-range=10.1.1.10,10.1.1.110,6h #设置dhcp地址范
    
    killall named
    killall hostapd
    ifconfig $port_out 192.168.7.1
    hostapd -B $hostapd_conf
    /etc/init.d/dnsmasq restart
    
    echo Sucess share wifi
    
    exit 0
}
    
stop( )
{
    echo Stopping share wifi ......
    echo Stop share Internet $port_in to $port_out
    
    # Configure iptable rules
    iptables -F
    
    # Log the message of route
    #iptables -A INPUT -m conntrack --ctstate NEW -p tcp --dport 80 -j LOG --log-prefix "NEW_HTTP_CONN: "
    
    # Save iptable rules
    sh -c "iptables-save > /etc/iptables.rules"
    
    # Configure hostapd
    hostapd_conf=/etc/hostapd/hostapd.conf
    [ -f $hostapd_conf ] && rm $hostapd_conf
    
    # Configure /etc/dnsmasq.conf
    
    killall named
    killall hostapd
    ifconfig $port_out down
    ifconfig $port_out del 192.168.7.1
    ifconfig $port_out up
    
    echo Sucess stop share wifi
    
    exit 0
}
#port_in is the network interface which connected to Internet, and default wlan1.
port_in=wlan1

#port_out is the network interface which will be setup AP, and default wlan0.
port_out=wlan0

if [ -n "$2" ]; then
    port_in=$2
    
    if [ -n "$3" ]; then
        port_out=$3
    fi
fi
    
case "$1" in
    "help" )
        help ;;
    "start" )
        start ;;
    "stop" )
        stop ;;
    *)
        help ;;
esac
    
# end file: sharewifi

PS. “二奶”升级到Lubuntu 12.04 LTS，感觉更好用了～