How To Fix No Wireless Network In Ubuntu 14.04 and 14.10

Solution 1:-

There have been plenty of reports regarding WiFi issues on Ubuntu 16.04. The majority of issues seems to stem from suspend/resume issues where the network would not re-connect, show the wrong icon in the top bar or similar.
The temporary workaround for this is to restart the network manager if you have no network at all, or, if you have network but the nm applet is showing the wrong status, just restart the nm applet.
Restart network manager.

sudo service network-manager restart

Restart the nm applet.

killall nm-applet && nm-applet &

How to fix it

So, this might or it might not work for you dep. on what issue you've been experiencing. But this did solve it for me on two different laptops.
Lets start with figuring out what WiFi chip we have.

sudo lshw -class network

The result should look something like this:

snews@TuxBook:~$ sudo lshw -class network
  *-network               
       description: Wireless interface
       product: Wireless 7265
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlp2s0
       version: 59
       serial: 60:57:18:78:f9:92
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwlwifi driverversion=4.4.0-28-generic firmware=16.242414.0 ip=192.168.1.20 latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn
       resources: irq:49 memory:f7000000-f7001fff

With the above information available to us we can go to work and try to solve the resume from suspend issue.

sudo vi /etc/pm/config.d/config

In this file, paste the following

SUSPEND_MODULES="iwlwifi wlp2s0" 

The values for the suspend_modules dep. on the output from the lshw command. In my case I see that my driver is named iwlwifi and that the logical name for my chip is wlp2s0. Hence I add those to the suspend_modules line.
Now, issue a restart of the network manager

sudo service network-manager restart

Now you should be able to suspend your laptop and when you resume it, WiFi should get reconnected automatically, and you should see the correct network type indicator in the nm applet.
The above might also work for you, so give it a try and see what happens.
UPDATE: It seems that as of 16.04.1 this is not an issue for me any more.
Resources:
http://askubuntu.com/questions/762198/16-04-lts-wifi-connection-issues - This details the /etc/pm/config.d/config config, but I had to modify it a little bit to make it work on my two laptops.

 Solution 2:-
 
After dual booting Macbook Air with Ubuntu, when I logged in to Ubuntu, I found that Ubuntu did not detect any wireless network. Networking was on but it said ‘no network devices available‘.

Indeed it is a common issue with Broadcom network adapters in Ubuntu. A relief is that Ubuntu provides additional drivers specifically for Broadcom adapters. But the issue is that to install additional drivers in Ubuntu you will need network connection. If you have wired connection, it will be very easy to install the additional drivers. But if you are restricted to wireless network only, you’ll have to look for alternate methods.

Since there are no Ethernet ports in Macbook Air and I didn’t want to buy an additional accessory just for this, as an alternate, I used the Ubuntu ISO image which I had used for installing Ubuntu. Let’s see how to fix no wireless network in Ubuntu 14.04 and 14.10 by installing additional drivers from CD-ROM.

Fix no wireless network detected in Ubuntu 14.04 and 14.10

First find out the network adapter in your system. You can refer to this article to find out make of wireless network adapter in Linux. In fact, you can just check in Software Sources if there are any additional drivers available for your system or not. If there are propriety drivers available, this method will easily work for you. Also, you will need the ISO image of the same Ubuntu version.

Step 1:

Get the ISO image of Ubuntu. If you just had a fresh install, you must have this ISO image in some other system or same system in another OS in dual boot. Copy it to an external device such as USB or DVD. Just copy it, don’t burn it as bootable USB.

Now boot in to Ubuntu and copy this Ubuntu ISO image to your home directory.

Step 2:

Open a terminal (Ctrl+Alt+T) and use the following commands:

sudo mkdir /media/cdrom
cd ~
sudo mount -o loop ubuntu-* /media/cdrom

Basically we just manually mounted the ISO image as if it was a CD.

Step 3:

Go to Unity Dash and look for Software & Updates:

In the first tab Ubuntu Software, check the option of CD Rom with Ubuntu…

It will ask for your password and reload the software sources. Next is to go in Additional Drivers tab and select the propriety driver and click on Apply Changes.

Once the drivers have been installed, you’ll see that Ubuntu now recognizes the wireless networks in range.

I hope this post helped you to fix no wireless network issue in Ubuntu 14.04. If you have questions or suggestions, feel free to drop a comment.