目標: 測試四核 A53 樹莓派 Raspberry Pi 3B+ 無線路由器, 輕量級WEB 服務器(Nginx,PHP,Sqlite3),UART 串口數據採集性能
初始配置，部分選項需要sudo reboot 重啓後生效
開啓 ssh 功能等
$ sudo raspi-config
更換爲國內軟件源，以加快軟件更新和安裝速度:
$sudo vi /etc/apt/sources.list
#添加內容
deb http://mirrors.aliyun.com/raspbian/raspbian/ stretch main contrib non-free rpi
系統更新及軟件升級
$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get dist-upgrade
$ sudo rpi-update
安裝輸入法
$sudo apt install fcitx
無線路由器軟件安裝
(hostapd: 軟件能使無線網卡工作在軟AP（Access Point）模式，即無線路由器,dnsmasq 軟件提供DHCP和DNS服務, pppoeconf 網絡拔號軟件)
$ sudo apt-get install dnsmasq hostapd pppoeconf
raspbian 系統中默認使用 dhcpd 來配置網絡，因 wlan0 工作在AP模式，所以需要設爲靜態IP地址，故在配置文件 /etc/dhcpcd.conf中禁用wlan0.
$sudo vi /etc/dhcpcd.conf
#內容
#interface eth0
#fallback static_eth0
denyinterfaces wlan0
在 /etc/network/interfaces 設置網卡的靜態IP地址
$sudo vi /etc/network/interfaces
source-directory /etc/network/interfaces.d
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address 192.168.0.250
netmask 255.255.255.0
gateway 192.168.0.1
allow-hotplug wlan0
iface wlan0 inet static
address 192.168.10.1
netmask 255.255.255.0
hostapd 配置文件
$sudo vi /etc/hostapd/hostapd.conf
#內容
# This is the name of the WiFi interface we configured above
interface=wlan0
# Use the nl80211 driver with the brcmfmac driver
driver=nl80211
# This is the name of the network
ssid=RPI_3B_Router
# Use the 2.4GHz band
hw_mode=g
# Use channel 6
channel=6
# Enable 802.11n
ieee80211n=1
# Enable WMM
wmm_enabled=1
# Enable 40MHz channels with 20ns guard interval
ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]
# Accept all MAC addresses
macaddr_acl=0
# Use WPA authentication
auth_algs=1
# Require clients to know the network name
ignore_broadcast_ssid=0
# Use WPA2
wpa=2
# Use a pre-shared key
wpa_key_mgmt=WPA-PSK
# The network passphrase
wpa_passphrase=raspberry
# Use AES, instead of TKIP
rsn_pairwise=CCMP
hostapd 配置文件啓動設置
$sudo vim /etc/default/hostapd
// 找到“#DAEMON_CONF=”,去掉#註釋，補全爲
DAEMON_CONF="/etc/hostapd/hostapd.conf"
完成配置後,檢查是否配置成功
$sudo /usr/sbin/hostapd /etc/hostapd/hostapd.conf
如果最後兩行出現瞭如下，則爲正常
wlan0: interface state UNINITIALIZED->ENABLE
wlan0: AP-ENABLED
重啓hostapd
$sudo service hostapd restart
如啓動不成功的處理辦法
$sudo systemctl disable dhcpcd
$sudo systemctl enable networking
$sudo reboot
$sudo hostapd -B /etc/hostapd/hostapd.conf #開機後再次啓動hostapd服務
dnsmasq 配置
$sudo vim /etc/dnsmasq.conf
#內容
interface=wlan0 # Use interface wlan0
listen-address=192.168.10.1 # Explicitly specify the address to listen on
bind-interfaces # Bind to the interface to make sure we aren't sending things elsewhere
server=8.8.8.8 # Forward DNS requests to Google DNS
domain-needed # Don't forward short names
bogus-priv # Never forward addresses in the non-routed address spaces.
dhcp-range=192.168.10.100,192.168.10.200,12h # Assign IP addresses between 172.24.1.50 and 172.24.1.150 with a 12 hour lease time
重啓 dnsmasq 服務
$sudo service dnsmasq restart
開啓Linux內核的IP轉發以及使用iptables做NAT表，讓無線網卡的數據通過有線網卡轉發出去
開啓Linux內核的IP轉發功能
$sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
開啓樹莓派有線網卡和無線網卡的轉發功能 (手動命令行開啓，如不保存，重新開機則會失效)
$sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
$sudo iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
$sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
保存當前的防火牆策略到配置文件中
$sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"
修改系統啓動腳本，添加啓動任務
$sudo vim /etc/rc.local
#新增內容
sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
iptables-restore < /etc/iptables.ipv4.nat
exit 0
dnsmasq經常會出現問題，原因是wlan0還沒熱啓動完成，而dnsmasq先啓動了，所以出現了啓動失敗的現象。
這裏的解決方案就是採用延時啓動
在 /etc/rc.local 文件中, exit 0 之前加入以下命令
$sudo bash /etc/dnsmasq_delayinit.sh
建立文件 dnsmasq_delayinit.sh
$sudo vim /etc/dnsmasq_delayinit.sh
#內容
#!/bin/sh
sleep 10
sudo service dnsmasq restart
把 dnsmasq_delayinit.sh 設置成可執行
$sudo chmod +x /etc/dnsmasq_delayinit.sh
待繼續測試和完善....