wireless - Ubuntu 16.04, Acer laptop, Broadcom driver and wifi cannot be enabled - Ask Ubuntu

ingredients

• laptop acer aspire v11 touch
• ubuntu 16.04 (kernel 4.4.0-45)
• additional driver 'broadcom 802.11 linux sta wireless device' in use

• lspci -knn | grep net -a2

  02:00.0 network controller [0280]: broadcom limited bcm43142 802.11b/g/n [14e4:4365] (rev 01) subsystem: foxconn international, inc. bcm43142 802.11b/g/n [105b:e07e] kernel modules: bcma, wl

• rfkill list

  0: acer-wireless: wireless lan soft blocked: no hard blocked: no 1: acer-bluetooth: bluetooth soft blocked: no hard blocked: no 2: hci0: bluetooth soft blocked: no hard blocked: no

issue

i cannot see option enable wireless device applet main menu bar. result cannot activate , use wi-fi.

research

i almost-fully aware of extensive post on installing broadcom wireless drivers, installation not point. however, have followed uninstall/install sequence:

sudo apt-get purge bcmwl-kernel-source sudo apt update sudo update pciids sudo apt install firmware-b43-install sudo reboot sudo apt install bcmwl-kernel-source # corresponds pci id 14e4:4365 (rev 01) sudo rfkill unblock # measure 

to no avail. note @ sudo apt install bcmwl-kernel-source dialogue window asks permission disable secure boot typing ad hoc password. claims asked later, although did not see being asked again.

interestingly, bounty-winning answer https://askubuntu.com/a/199154/446253, see lspci -nn | grep -i bcm network controller bcm43142 might not supported sta driver. way esoteric me, may provide clue expert.

i aware of other posts deal earlier ubuntu versions, dearly avoid guesswork , find answer applies 16.04 safely.

question

please provide list of simple steps regain possibility enable wifi menu bar?

if need refer verbose posts, please indicate answer applicable according , in way integrates actions undertaken above.

in experience problem comes either of 2 reasons, or both:

1. secure boot in boot set-up utility enabled. should disabled instead. user pilot6 pointing out in comments above.

2. a new kernel not cope network , wi-fi settings. in case solution 1 works kernel 3.19.0-77-generic or 4.4.0-45-generic, not later 4.4.0-53-generic. splash older reliable kernel, @ boot time go 'advanced ubuntu options' of boot loader rather using standard 'ubuntu'. presented choice @ restart since have dual boot system: if don't, can press shift key @ boot time have choice presented you. see https://askubuntu.com/a/885850/446253 way select earlier kernel version boot-time default automatically, using grub customizer.

to know kernel system running on type uname -r in command line (the output subset of uname -a).

this problem occurred both ubuntu 14.04 , 16.04. presume release specification immaterial.