樹莓派的無線網絡卡安裝
首先，從網上買一個適用於樹莓派的無線網絡卡，一般大家都推薦EDUP
0 準備工作，插入USB無線網絡卡之前，檢查網路介面狀態。當然，這時候還是插著網線的。
$ ifconfig
eth0 Link encap:Ethernet HWaddr b8:27:eb:75:29:09
inet addr:192.168.2.109 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:232 errors:0 dropped:0 overruns:0 frame:0
TX packets:145 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26447 (25.8 KiB) TX bytes:25209 (24.6 KiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
1 插入USB的無線網絡卡，網路介面是這樣的，出現了wlan0，就是我們的無線網絡卡
可以使用命令sudo lsusb 檢視掛載的USB裝置，也可以看到我們的無線網絡卡
當然，這時候無線網絡卡還沒有配置好，不能正常工作
$ ifconfig
eth0 Link encap:Ethernet HWaddr b8:27:eb:75:29:09
inet addr:192.168.2.109 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:232 errors:0 dropped:0 overruns:0 frame:0
TX packets:145 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26447 (25.8 KiB) TX bytes:25209 (24.6 KiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
wlan0 Link encap:Ethernet HWaddr e8:4e:06:26:d2:4d
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
$ sudo lsusb
Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 001 Device 004: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter
2 修改樹莓派的網絡卡配置，藍色部分是新加的無線配置。
這裡使用靜態IP地址，方便以後ssh遠端連線。
$ sudo vim /etc/network/interfaces
auto lo
iface lo inet loopback
#iface eth0 inet dhcp
iface eth0 inet static
address 192.168.2.109
netmask 255.255.255.0
gateway 192.168.2.1
#allow-hotplug wlan0
#iface wlan0 inet manual
#wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
#iface default inet dhcp
auto wlan0
allow-hotplug wlan0
iface wlan0 inet static
wpa-ssid "your_ssid"
wpa-psk "your_password"
address 192.168.2.110
netmask 255.255.255.0
gateway 192.168.2.1
3 執行下面的命令，重啟網路介面。
這時候，拔掉網線，無線網絡卡應該能夠正常工作了。如果不行，power cycle一下樹莓派。
$ sudo /etc/init.d/networking restart
最後，如果一起正常，網絡卡狀態如下。
注意，我發現這個無線網絡卡如果長時間不用，好像就inactive了。需要主機ping一下，重新ssh一下才好用，搞不懂是怎麼回事？
$ ifconfig
eth0 Link encap:Ethernet HWaddr b8:27:eb:75:29:09
inet addr:192.168.2.109 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:12 errors:0 dropped:0 overruns:0 frame:0
TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:558 (558.0 B) TX bytes:250 (250.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
wlan0 Link encap:Ethernet HWaddr e8:4e:06:26:d2:4d
inet addr:192.168.2.110 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:81 errors:0 dropped:0 overruns:0 frame:0
TX packets:103 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:11361 (11.0 KiB) TX bytes:16209 (15.8 KiB)