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I had recently updated to Ubuntu 18.04. All was working fine until today morning when I was not able to connect to the wifi. When I try to scan for networks it shows no networks found. When I run iwlist wlo1 scan I get the following results:

wlo1 No scan results

I had the same problem with Ubuntu 16.04 but managed to fix by changing the antenna_sel parameter as per this and this by using:

sudo modprobe -r rtl7823be 
sudo modprobe rtl8723be ant_sel=x

The value of x being either 1 or 2, whichever gives better results for wifi signals. However, when I try the same solution for 18.04 it doesn't seem to work. I have looked for solutions for 18.04 and found this answer this answer. There deosn't seem to be any conclusive answer on how to fix the problem. I decided to uninstall rtl8723be drivers using sudo apt purge rtl8723be and reinstall using this however when I try to do that I get errors (when I run this command sudo add-apt-repository ppa:hanipouspilot/rtlwifi) such as:

E: The repository 'http://ppa.launchpad.net/hanipouspilot/rtlwifi/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.

I then installed the rtl8723be driver using instructions as per the github page for rtlwifi_new in here. The installation was sucessful however I was back to square one, no wifi networks found. Does anyone know how to get the wireless to working? I'll post the output of lshw -class network below:

  *-network                 
   description: Wireless interface
   product: RTL8723BE PCIe Wireless Network Adapter
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0
   bus info: pci@0000:08:00.0
   logical name: wlo1
   version: 00
   serial: 70:77:81:12:fc:2d
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
   configuration: broadcast=yes driver=rtl8723be driverversion=4.15.0-33-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11
   resources: irq:18 ioport:5000(size=256) memory:c6100000-c6103fff


*-network
   description: Ethernet interface
   product: RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0
   bus info: pci@0000:09:00.0
   logical name: eno1
   version: 0a
   serial: 3c:a8:2a:ae:31:82
   size: 100Mbit/s
   capacity: 100Mbit/s
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8107e-2_0.0.2 02/26/15 ip=145.94.38.86 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s
   resources: irq:19 ioport:4000(size=256) memory:c6004000-c6004fff memory:c6000000-c6003fff

PS: The LAN works just fine, the problem is just with the wireless interface.

EDIT: The problem is solved with an update to 18.10 as it uses kernel 17.0.

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I am afraid I don't have an exact answer to your question, but I am having the exact same problem and found a workaround to get my wifi running on my laptop again.

Run in terminal: uname -r
Does it say 4.15.0-33-generic?

My solution:
When booting the laptop, select advanced startup options (as if you were trying to select recovery mode) and select kernel 4.15.0-32-generic.
(When entering this menu, I had multiple options/kernels to choose from - some were listed as (recovery mode) and others were normal - I chose the non-recovery entry.) I will try to google my way to a better fix and post back if I find it.

  • Wow! That worked, wifi is working again! Thanks! – srikarad Aug 28 '18 at 10:00
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Try some basic: Plug wifi dongle in a different usb port. make sure you have the latest version of the following installed: linux-headers-generic build-essential git. Try putting your module in etc/modules to load at boot. Verify module is not in the blacklist file. Make sure your on the latest release of 18.4 Apt-get update & upgrade. Bring down your network manager then restart it.

TC.

  • Tried all of it, unfortunately, nothing worked! However, the solution by @Evros of changing the kernel from 4.15.0-33-generic to 4.15.0-32-generic in the advance options worked! – srikarad Aug 28 '18 at 10:03
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The bug is fixed with this kernel:

http://kernel.ubuntu.com/~jsalisbury/lp1788997

as long as you select antenna 1:

modprobe rtl8723be ant_sel=1

Make sure you have that in config too:

sudo /bin/sh -c 'echo "options rtl8723be ant_sel=1" >> /etc/modprobe.d/rtl8723be.conf'

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