一.背景
1.1 jello@jello:~$ lsb_release -a
No LSB modules are available.
Distributor ID:    Ubuntu
Description:    Ubuntu 16.04.3 LTS
Release:    16.04
Codename:    xenial
1.2 usb无线网卡
jello@jello:~$ lsusb|grep Wireless
Bus 001 Device 003: ID 0bda:8179 Realtek Semiconductor Corp. RTL8188EUS 802.11n Wireless Network Adapter
1.3 usb无线网卡使用的驱动
jello@jello:~$ lsmod |grep 8188
r8188eu               454656  0
cfg80211              565248  2 wl,r8188eu
1.4 列出当前的无线网卡设备的当前状态
jello@jello:~$ sudo rfkill list
0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
1: brcmwl-0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
1.5 列出指定无线网卡的配置情况
jello@jello:~$ sudo iwconfig wlan1
wlan1     unassociated  Nickname:"<WIFI@REALTEK>"
          Mode:Managed  Frequency=2.412 GHz  Access Point: Not-Associated   
          Sensitivity:0/0  
          Retry:off   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0
从此处可以看出当前网卡处于2.412GHz的频率
1.6 列出要连接的无线信号的信息
jello@jello:~$ sudo iwlist wlan1 scan
ell 10 - Address: 62:38:3A:43:12:C3
                    ESSID:"myWifi"
                    Protocol:IEEE 802.11bgn
                    Mode:Master
                    Frequency:2.472 GHz (Channel 13)
                    Encryption key:on
                    Bit Rates:144 Mb/s
                    Extra:wpa_ie=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : TKIP CCMP
                        Authentication Suites (1) : PSK
                    Extra:rsn_ie=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : TKIP CCMP
                        Authentication Suites (1) : PSK
                    Quality:0  Signal level:0  Noise level:0
从此处可以看出要连接的wifi使用的chan=13
1.7 列出网卡支持的frequency
jello@jello:~$ sudo iwlist wlan1 frequency
wlan1     13 channels in total; available frequencies :
          Channel 01 : 2.412 GHz
          Channel 02 : 2.417 GHz
          Channel 03 : 2.422 GHz
          Channel 04 : 2.427 GHz
          Channel 05 : 2.432 GHz
          Channel 06 : 2.437 GHz
          Channel 07 : 2.442 GHz
          Channel 08 : 2.447 GHz
          Channel 09 : 2.452 GHz
          Channel 10 : 2.457 GHz
          Channel 11 : 2.462 GHz
          Channel 12 : 2.467 GHz
          Channel 13 : 2.472 GHz
          Current Frequency=2.412 GHz (Channel 1)

二.连接chan=13的wifi无线信号
2.1 启动无线网卡(笔者的usb无线网卡对应的名字为wlan1,请根据自己的情况选择)
sudo ifconfig wlan1 up  
2.2 连接加密的chan=13的无线网(wpa_supplicant.conf文件中有无线网的信息)
jello@jello:~$sudo wpa_supplicant -B -iwlan1 -c wpa_supplicant.conf
2.3 通过2.2出现以下错误提示
Successfully initialized wpa_supplicant
nl80211: Could not configure driver mode
nl80211: deinit ifname=wlan1 disabled_11b_rates=0
wlan1: Failed to initialize driver interface
2.4 解决2.3的错误提示
jello@jello:~$ sudo wpa_supplicant -B -iwlan1 -c wpa_supplicant.conf -Dwext
Successfully initialized wpa_supplicant
ioctl[SIOCSIWAP]: Operation not permitted
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
不用管这些错误信息
2.5 获取ip
jello@jello:~$ sudo dhclient wlan1