TurnRPIIntoAP

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目的

将闲置的RPI变为一个AP,有线转无线，用于快速连接网络开发。

准备材料

下载2021-05-07-raspios-buster-armhf-lite.zip， 解压并写入SD卡，之后用SD卡启动RPI3, 默认用户名及密码是pi/raspberry, 写入后使用rpi-config扩充文件系统：

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.10.52-v7+ #1441 SMP Tue Aug 3 18:10:09 BST 2021 armv7l GNU/Linux
pi@raspberrypi:~ $ cat /etc/issue
Raspbian GNU/Linux 10 \n \l

步骤

更改为tsinghua的源以加速:

# 编辑 `/etc/apt/sources.list` 文件，删除原文件所有内容，用以下内容取代：
deb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main non-free contrib rpi
deb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main non-free contrib rpi

# 编辑 `/etc/apt/sources.list.d/raspi.list` 文件，删除原文件所有内容，用以下内容取代：
deb http://mirrors.tuna.tsinghua.edu.cn/raspberrypi/ buster main ui

下载hostapd及dhcp服务器:

# sudo apt-get update -y
# sudo apt-get upgrade -y
# sudo apt-get install hostapd isc-dhcp-server iptables-persistent

配置DHCP服务器:

$ sudo vim /etc/dhcp/dhcpd.conf

找到以下行(这里需要注释掉默认的选项):

option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;

替换为:

#option domain-name "example.org";
#option domain-name-servers ns1.example.org, ns2.example.org;

找到以下行(这里是激活authoritative选项):

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

替换为:

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
authoritative;

在文件的末尾添加以下定义:

subnet 172.16.42.0 netmask 255.255.255.0 {
	range 172.16.42.10 172.16.42.50;
	option broadcast-address 172.16.42.255;
	option routers 172.16.42.1;
	default-lease-time 600;
	max-lease-time 7200;
	option domain-name "local";
	option domain-name-servers 8.8.8.8, 8.8.4.4;
}

现在保存后退出。
现在编辑isc-dhcp-server的默认定义文件，配置其监听的端口:

# sudo vim /etc/default/isc-dhcp-server
.....
INTERFACESv4="wlan0"
INTERFACESv6="wlan0"

编辑wlan0的静态地址(这里我们顺便设置了eth0的静态地址):

# sudo vim /etc/network/interfaces
auto wlan0
iface wlan0 inet static
  address 172.16.42.1
  netmask 255.255.255.0
auto eth0
iface eth0 inet static
  address 192.168.1.117
  netmask 255.255.255.0
  gateway 192.168.1.33

配置hostapd:

# sudo vim /etc/hostapd/hostapd.conf
country_code=US
interface=wlan0
driver=nl80211
ssid=Pi_AP
country_code=US
hw_mode=g
channel=6
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=xxxxxxxxxxxx
wpa_key_mgmt=WPA-PSK
wpa_pairwise=CCMP
wpa_group_rekey=86400
ieee80211n=1
wme_enabled=1

配置hostapd的默认配置文件:

# sudo vim /etc/default/hostapd
Find the line #DAEMON_CONF="" and edit it so it says DAEMON_CONF="/etc/hostapd/hostapd.conf"

配置NAT（网络地址转换) :

# sudo vim /etc/sysctl.conf

pi@raspberrypi:~ $ cat /etc/sysctl.conf  | grep ip_forward
net.ipv4.ip_forward=1

最后保存iptables:

sudo iptables -t nat -S
sudo iptables -S
sudo sh -c "iptables-save > /etc/iptables/rules.v4"

iptables-persistent会在启动的时候自动载入保存的规则。

如此则可以将RPi3作为一个无线接入点来使用。