ubuntu WiFi: operation not possible due to RF-kill《轉載》

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 Some people have been experiencing WiFi problems with Ubuntu 10.10 since an update that happend just before Christmas 2010. The problem seems to be a bug in a kernel module, which prevents the rfkill‘s soft and hard block from syncing correctly.

In practice that means you can press your laptop‘s WiFi button as often as you want, it doesn‘t change anything. Your wireless adapter will always appear as disabled. If you try to start the wireless interface manually you get the following error message:

[email protected]:~# sudo ifconfig wlan0 up
SIOCSIFFLAGS: Operation not possible due to RF-kill

If you do a rfkill list all you should get an output similar to this:

[email protected]:~$ sudo rfkill list all
0: hp-wifi: Wireless LAN
Soft blocked: yes
Hard blocked: no
1: phy0: Wireless LAN
Soft blocked: yes
Hard blocked: no

Depending on the state of your WiFi button the Hard blocked will either be yes or no. Press the WiFi button and run rfkill list all again to make sure the value for Hard blocked changes.

The actual problem is, that the Soft blocked value is always set to yes, because for some reason the syncing between the hardware block and the software block doesn‘t work as supposed. To override this behavior, you can just run rfkill unblock wifi and it should work again. Double check by entering rfkill list all again and make sure it looks like this, with all values set to no:

[email protected]:~$ sudo rfkill list all
0: hp-wifi: Wireless LAN
Soft blocked: no
Hard blocked: no
1: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no

If you then run ifconfig wlan0 up (or enable the wireless via your desktop‘s network manager) you should be able to connect to a wireless network again without any further issues.

The configuration, which I‘ve been using:

• Compaq Presario CQ60
• Atheros AR5001 Wireless Network Adapter
• Ubuntu 10.10

I also read, that some people could fix it, by turning off the WiFi button during the boot process and then switch it on again, once the system is up and running. It seems that the system expects the hard block to be set to off. This is still a bug, but it could explain why then the soft block didn‘t sync with the hard block any more.《FROM:http://blog.csdn.net/cat_lover/article/details/7088873》==================================UBUNTU14.04也出現過同樣的問題，按如上操作後重新啟動電腦才能串連到WIFI。操作步驟是這個的，首先按膝上型電腦的快速鍵或開關關閉無線網，然後執行sudo rfkill list all---->ifconfig wlan0 up--->重啟電腦。

查看 網卡啟用狀態：

執行ifconfig -a 顯示所有網卡資訊， 不加-a參數，只能查啟用的網卡。
例如：網卡名 eth0
啟用網卡命名 ifconfig eth0 up
禁用網卡命名 ifconfig eth0 down

ubuntu WiFi: operation not possible due to RF-kill《轉載》