Mysql Uninstall from Ubuntu 16.04

Follow the steps

1) sudo apt-get remove dbconfig-mysql
2) sudo apt-get remove --purge mysql-server mysql-client mysql-common

iperf3 compilation for ARM in Ubuntu

For compiling for ARM target board

Get the cross compiler details and pass it as argument to the configure script. I used iperf-3.1.3
Below method is for building iperf3 as static, so that we need to push only the iperf3 binary , without any shared libraries

First this assumes you had set the ARM compiler in the path

cd iperf-3.1.3/

1) ./configure --host=arm-linux-gnueabi CC=arm-linux-gnueabi-gcc CXX=arm-linux-gnueabi-g++ CFLAGS=-static CXXFLAGS=-static --enable-static --prefix=`pwd`/output

2) make install


the binary will be available inside output/bin/

Increasing the linux terminal console column width and number of rows

very useful tip for embedded Linux engineers and those who work with Linux Console using minicom or teraterm

very useful tip for embedded Linux engineers and those who work with Linux Console using minicom or teraterm

normally if we type ps in serial console, it will show the process , if the length is more than 80 character(which is default) we cannot see the string after 80 characters in the consol,

with the below command you can adjust the width of the terminal with cols argument and number of rows using the  argument rows to the command stty

stty cols 160 rows 40

this can be used separate also

stty cols 160

stty rows 50

Hope this help in ps and htop command when u run and other applications

accessing serial port in linux/ubuntu as a normal user

For accessing serial port in linux/ubuntu as a normal user,

we need to add the user to the dialout group

follow the below commands 

sudo adduser second_user dialout

or 

sudo adduser `whoami` dialout 

Linux File Permission in octal format in terminal or command line

To see the file permission in Linux terminal use the below command

stat -c "%a %n" *

* = will list and show all files , replace with the fie name if you want to know only for one filename

virtual machine shared folder permission

When using Ubuntu on Virtual Box, you can share a folder between Windows Hosta and Ubunut Guest, after doing the sharing, you need to set the permission so that it can be accessed using the normal user login



You need to type the followinf command to add the permission for the normal user to access it

sudo usermod -aG vboxsf <youruser_name>

or

sudo usermod -aG vboxsf `whoami`

Wi-Fi command line commands

Wi-Fi(IEEE 802.11) command line useful commands

Wi-Fi AP Mode
1) Scan the network

iw dev wlan0 scan or
iw dev wlan0 scan ap-force

2) Connected Devices to the Wi-Fi Access Point (wifi AP mode)

Using hostapd cli:  hostapd_cli all_sta

using iw: iw dev wlan0 station dump


Wi-Fi Station/Client Mode

1) To Scan network

iw dev wlan0 scan 

to show only the SSID from the ouput

iw dev wlan0 scan | grep SSID