unblock wifi in rfkill

rfkill block问题

之前在部署arch linux时比较偷懒，没有采用正规的网络设置方法，而是使用脚本来启动有线和无线网络。

• start_lan

sudo wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant-my_wifi.conf -D wired -i enp0s25 &
sleep 5
sudo dhcpcd enp0s25

• start_wifi

sudo ifconfig wlp3s0 down
sleep 1
sudo ifconfig wlp3s0 up
sudo wpa_supplicant -B -c /etc/wpa_supplicant/wpa_supplicant-my_wifi.conf -i wlp3s0
sleep 5
sudo dhcpcd wlp3s0

但是我发现发现无线脚本运行时候报错

SIOCSIFFLAGS: Operation not possible due to RF-kill
Successfully initialized wpa_supplicant
rfkill: WLAN soft blocked
dhcpcd-9.2.0 starting
DUID 00:04:62:91:a1:81:51:17:11:cb:b7:60:eb:9e:7a:2e:cc:7b
dhcpcd_prestartinterface: Operation not possible due to RF-kill
wlp3s0: waiting for carrier
timed out
dhcpcd exited

为何会出现 rfkill: WLAN soft blocked 报错？

参考 How to unblock something listed in rfkill?

• 检查 rfkill

rfkill list all

显示无线接口存在 Soft blocked

0: tpacpi_bluetooth_sw: Bluetooth
    Soft blocked: no
    Hard blocked: no
1: hci0: Bluetooth
    Soft blocked: no
    Hard blocked: no
2: phy0: Wireless LAN
    Soft blocked: yes
    Hard blocked: no

"Hard blocked" 不能通过软件修改，需要检查是否是硬件开关关闭，例如ThinkPad笔记本的侧边有一个硬件拨动开关可以关闭无线设备

"Soft blocked" 是软件关闭，例如失败的驱动或者内核模块导致连接断开

• 解除block: 这里可以看到无线接口是 2: phy0: Wireless LAN ，所以使用这个标号就是 2

rfkill unblock 2

• 然后再次 rfkill list all 检查就可以看到软件阻断已经关闭

0: tpacpi_bluetooth_sw: Bluetooth
    Soft blocked: no
    Hard blocked: no
1: hci0: Bluetooth
    Soft blocked: no
    Hard blocked: no
2: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no

• 再次执行

./start_wifi

但是提示无法从驱动读取 SSID

Successfully initialized wpa_supplicant
wlp3s0: Could not read SSID from driver
dhcpcd-9.2.0 starting
DUID 00:04:62:91:a1:81:51:17:11:cb:b7:60:eb:9e:7a:2e:cc:7b
wlp3s0: waiting for carrier
timed out
dhcpcd exited

我发现可能是我在 /etc/wpa_supplicant/wpa_supplicant-my_wifi.conf 有一个配置影响了SSID获取

ap_scan=0

将这个配置修改成 ap_scan=1 ，即

ctrl_interface=/var/run/wpa_supplicant
ap_scan=1
network={
  ssid="my_wifi"
  key_mgmt=WPA-EAP
  eap=PEAP
  phase1="peaplabel=0"
  phase2="auth=MSCHAPV2"
  identity="my_id"
  password="my_passwd"
}

然后再执行

sudo wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant-my_wifi.conf -i wlp3s0

则正常连接成功，此时使用 iwconfig 可以看到

...
wlp3s0    IEEE 802.11  ESSID:"my_wifi"
          Mode:Managed  Frequency:5.745 GHz  Access Point: xx:xx:xx:xx:xx:xx
          Bit Rate=12 Mb/s   Tx-Power=15 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=53/70  Signal level=-57 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0
...

完整配置

确保无线网卡已经激活

• 首先使用 rfkill 确保无线网卡已经激活

sudo apt install rfkill

• 检查无线网卡状态

rfkill list

如果wifi被软件block，需要unblock

rfkill unblock wifi

• 停止NetworkManager(如果是Ubuntu桌面版本，通常需要停止NetworkManager)

sudo systemctl stop NetworkManager
sudo systemctl disable NetworkManager

检查无线网卡接口

• 使用iwconfig命令检查

iwconfig

显示输出

lo        no wireless extensions.

enp0s25   no wireless extensions.

wlp3s0    IEEE 802.11  ESSID:off/any
          Mode:Managed  Access Point: Not-Associated   Tx-Power=15 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off

virbr0    no wireless extensions.

virbr0-nic  no wireless extensions.

anbox0    no wireless extensions

这里可以看到 Access Point: Not-Associated

如果无线接口没有显示，可能需要激活:

sudo ifconfig wlp3s0 up

• 然后扫描无线网络：

sudo iwlist wlp3s0 scan | grep ESSID

此时可以看到周围可用的无线热点名字列表

使用wpa_supplicant连接无线网络

• 安装wpa_supplicant

sudo apt install wpasupplicant

• wapsupplicant提供了一个 wpa_passphrase 工具可以创建配置:

wpa_passphrase your-ESSID your-passphrase | sudo tee /etc/wpa_supplicant/wpa_supplicant-home.conf

• 然后我们通过命令行就可以连接

sudo wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant-home.conf -i wlp3s0

如果终端显示的输出没有报错，就可以在命令行上添加 -B 参数以便在后台运行 wpa_supplicant 进程

sudo wpa_supplicant -B -c /etc/wpa_supplicant/wpa_supplicant-home.conf -i wlp3s0

• 连接正常，则使用 iwconfig 可以看到已经连接到无线Access Point

• 最后执行dhcp

sudo dhclient wlp3s0

连接隐藏的无线网络

如果无线网络是隐藏SSID，则需要在 wpa_supplicant.conf 配置中加上

scan_ssid=1

启动时自动连接

参考

• Turn WIFI on from the command line - Still off

• How to unblock something listed in rfkill?

• Using WPA_Supplicant to Connect to WPA2 Wi-fi from Terminal on Ubuntu 16.04 Server - 这片文档写得非常详细，建议阅读参考