hello I am on a brand new install of Ubuntu 15.04 on a lenovo b575 laptop everything is working but I can not enable the wifi. when I run the command "rfkill list all" everything listed says no except for "1: phy0: Wireless LAN" hard blocked says yes but my wifi switch is in the on position and the command "rfkill unblock all" does not work. I am not sure what to do from here, I would really appreciate it if someone would take the time to help.
I have looked up your Lenovo b575. Please make sure the PHYSICAL wifi switch on the front of the laptop is enabled. Two thirds of the time when I am asked to help with wifi issues, it is that the user inadvertently turned off their laptop's physical wifi switch.
I ended up fixing this problem by opening up my laptop disconnecting the wifi card. Then I started up the laptop with out the wifi card. After this I turned the laptop off and reconnected the wifi card. Now the command "rfkill list all" lists everything no and I am able to connect to my wifi again.