Ubuntu / Linux laptop WiFi issues

The beginning of that

I noticed that Wi-Fi is not available from the GUI settings of Ubuntu 18.04 LTS. The message "No Wi-Fi Adapter Found" or "No Wi-Fi Adapter Found" is displayed. Similarly, when I look at the Bluetooth column, I get a message that the Bluetooth device cannot be found. I had a wired connection for a while, so I didn't know when it happened.

It seems that a lot of similar troubles are occurring when I investigate, but it seems that this problem is troubled by the fact that there are multiple causes and the troubleshooting methods are quite diverse. In this post, I will give a command to confirm the cause and summarize what kind of recovery method should be done for each symptom. I hope it helps someone, and I'm happy to comment that this was the case in my environment.

trouble shooting

--Isn't it in AirPlane mode?

• Evaluation criteria --There is an airplane ✈ mark on the menu bar at the top of Ubuntu. ――It is clearly written in "Bluetooth" of "Settings" that it is airplane mode. --Recovery means --Turn off airplane mode from "Bluetooth" in "Settings" --Is Wi-Fi turned off?
• Evaluation criteria --When you open "Wi-Fi" in "Settings", the toggle switch at the top of the window is "OFF". --When you type the $ rfkill list command in the terminal, the SOFT column is blocked. --Recovery means --Click the toggle switch at the top of the "Wi-Fi" window in "Settings" to turn it "ON" --Type $ rfkill unblock wlan in the terminal --Is the Wireless key on your keyboard pressed?
• Evaluation criteria --When you type the $ rfkill list command in the terminal, the HARD column becomes blocked. --Nothing comes out when you type the $ rfkill list bluetooth command in the terminal --When you open "Settings", both Wi-Fi and Bluetooth appear when the device cannot be found. --Even if the toggle switch is turned "ON", it returns. --Recovery means --Find and hit the Wireless key on your keyboard ――In my case, this was it. PrtScr key along with Fn key on DELL XPS 13 --The wireless key mark and position vary considerably depending on the manufacturer and model number of the notebook PC. --Is it disabled at the BIOS level?
• Evaluation criteria --Check Wi-Fi and Bluetooth settings from the BIOS screen --The screen configuration of the BIOS differs depending on the PC, so check it according to your PC. --Recovery means --If it is "Disable", set it to "Enable" --Isn't there a device driver?
• Evaluation criteria --Type $ ip link show in the terminal to see the logical name of the Wi-Fi device --Names such as wlan0 and wlp1s0 are automatically assigned. --You may distinguish by MAC address --Type $ sudo lshw -C network in the terminal and check if driver = hoge is set in the configuration of the corresponding network. --If the Wi-Fi module is recognized as a PCI device, you can also check the device driver name in use with $ lspci -nnk --Recovery means --If not driver = hoge --Search for the device driver using the product as a clue when checking with the lshw command. --Realtek's rtlXXXX series is compiled and installed from github etc. --BUFFALO WI-U2-433DMS was available in [This Devadora] for Realtek (https://github.com/gnab/rtl8812au) --Broadcom's bcm series is installed with $ sudo apt install bcmwl-kernel-source --When driver = hoge --Type $ modinfo hoge in the terminal to check the device driver information --Type $ nmcli connection in the terminal --If the SSID of the Wi-Fi you want to use is not displayed, set the Wi-Fi network from the settings. --Type $ nmcli device in the terminal and check STATE using the device name as a clue. --If connected, you should be connected to Wi-Fi --Use commands such as $ dmesg | less and $ nano / var / log / syslog to visually check for any error messages.