How to

Topics

• Proxy

• SSH

• ZSH

Download files from the cloud

• Send content to WeTransfer cloud-like

• Download using wget

Installing wget

sudo apt install wget

Download a single file

wget https://wordpress.org/latest.zip

Save the downloaded file under a different name

To save the downloaded file under a different name, pass the -O option followed by the chosen name.

wget -O latest-wordpress.zip https://wordpress.org/latest.zip

How to download in the background mode with wget

To download in the background, use the option -b . In the following example, we are downloading the OpenSuse iso file in the background.

wget -b https://download.opensuse.org/tumbleweed/iso/openSUSE-Tumbleweed-DVD-x86_64-Current.iso

Download all files from FTP

wget -r 'ftp://username:password@ip/directoryname'

Download / Upload Files

Single file from remote to local

scp remoteuser@remoteserver:/remote/folder/myfile.txt  myfile.txt

Multiple files from local to remote

scp myfile.txt myfile2.txt remoteuser@remoteserver:/remote/folder/

All files from local to remote

scp * remoteuser@remoteserver:/remote/folder/

All files and folders recursively from local to remote

scp -r * remoteuser@remoteserver:/remote/folder/

References: Simplified Guide

DNS

Custom DNS

$ vim  /etc/resolv.conf   

nameserver 8.8.8.8
nameserver 8.8.4.4

Custom DNS servers for /etc/resolv.conf

To define a custom DNS:

• First, install resolvconf and follow the commands bellow

sudo apt install resolvconf -y

• Put the nameservers from Google inside the file/etc/resolvconf/resolv.conf.d/head

sudo sh -c "echo \"nameserver 8.8.8.8
nameserver 8.8.4.4\" >> /etc/resolvconf/resolv.conf.d/head"

sudo sh -c "echo \"nameserver 8.8.8.8
nameserver 8.8.4.4\" >> /etc/resolvconf/resolv.conf.d/base"

• Update Resolvconf

  sudo resolvconf -u

• Restart the resolvconf service

sudo service resolvconf restart

Get current IP from the shell

remoteHost=$(dig +short myip.opendns.com @resolver1.opendns.com)
echo $remoteHost

Stream audio

sudo apt install -y pulseaudio pavucontrol

• Alt + F2 and type pavucontrol

• Select Recording tab

• Change to Internal audio monitor

Search inside files recursively

grep -rli "my-name"

Display Usage in Megabytes and Gigabytes

df -h

Display a Specific File System

df –h /dev/sda2

Show size of folders

sudo du -shc /var/*

Empty trash

rm -rf ~/.local/share/Trash/*

Search and replace inside the file

sed -i 's/SEARCH_REGEX/REPLACEMENT/g' INPUTFILE

Network

Check network ports in use

sudo netstat -tlnp | grep 80

Check opened network ports of the server

nmap HOST

## Example

nmap google.com
nmap 55.1.22.5.68

Open network ports

# Openning 8080 port
 
 sudo iptables -A INPUT -p tcp --dport 8080 -j ACCEPT

Open Firewall ports

To open ports on the firewall, using the iptables command is possible specifying the desired port. Using the example below, just replace port 8888 with the desired port.

$ iptables -I INPUT -p tcp --dport 8888 -j ACCEPT
$ iptables -t filter -I FORWARD -i eth2 -o etho -m multiport --dport 8888 -j ACCEPT

Logs

Show real-time logs from OS

tail -f /var/log/syslog

# Or you can use journalctl
# journalctl -f

Environment

Set Global environment

sudo sh -c "echo MY_GLOBAL_ENV_TO_MY_CURRENT_DIR=$(pwd)" >> /etc/environment"

Set local environment

env MY_GLOBAL_ENV_TO_MY_CURRENT_DIR=$(pwd)

Unset local environment

unset MY_GLOBAL_ENV_TO_MY_CURRENT_DIR

Startup

Show all service status

sudo service --status-all 

Exec commands at startup

sudo vim /etc/init.d/rc.local

    #!/bin/bash

    #command1
    #command2
    exit 0;

sudo chmod ugo+x /etc/init.d/rc.local

update-rc.d rc.local defaults

PPA

Remove installed PPA repository

Use the "--remove" flag, similar to how the PPA was added:

sudo add-apt-repository --remove ppa:whatever/ppa

As a safer alternative, you can install "ppa-purge":

sudo apt-get install ppa-purge

And then remove the PPA, downgrading gracefully packages it provided to packages provided by official repositories:

sudo ppa-purge ppa:whatever/ppa

Note that this will uninstall packages provided by the PPA, but not those provided by the official repositories. If you want to remove them, you should tell it to apt:

sudo apt-get purge package_name

You can also remove PPAs by deleting the .list files from /etc/apt/sources.list.d directory.

Last but not least, you can also disable or remove PPAs from the "Software Sources" section in Ubuntu Settings with a few clicks of your mouse (no terminal needed).

Execute "add-apt-repository" without press enter

--force-yes

Force yes; this is a dangerous option that will cause apt to continue without prompting if it is doing something potentially harmful. It should not be used except in very special situations. Using force-yes can potentially destroy your system! Configuration Item: APT::Get::force-yes.

# Example
sudo add-apt-repository ppa:ondrej/php --force-yes

Create an alias for shell commands

• Add the script below at end of the file ~/.profile

alias hello_world="echo \"Hello World!\""

• Then type your alias directly

hello_world
# output: Hello World

Update packages less noisy

apt-get -qq update

Revalidade ca-certificates

sudo apt-get install -y --reinstall ca-certificates

Add multi-touch to your Linux distribution

To do it, make sure to do the steps below:

sudo gpasswd -a $USER input
sudo apt install xdotool wmctrl libinput-tools
git clone https://github.com/bulletmark/libinput-gestures
cd libinput-gestures
sudo ./libinput-gestures-setup install
touch ~/.config/libinput-gestures.conf

• Paste the content below inside ~/.config/libinput-gestures.conf:

gesture swipe up 3 xdotool key super+Down  
gesture swipe left 3 xdotool key super+Right  
gesture swipe right 3 xdotool key super+Left  

• After that execute the commands below

libinput-gestures-setup autostart
libinput-gestures-setup start
libinput-gestures-setup restart

References:

• https://github.com/bulletmark/libinput-gestures

• https://www.youtube.com/watch?v=ci6YbQGx3c4

Get SO information

sudo apt-get install screenfetch -y
screenfetch

Know where the program was installed

which php

Show any configured swap

sudo swapon --show

Observe and monitor system memory usage

• "-h" means Human Mode

  • Shows values in Mega or Giga

free -h

Downgrade Ubuntu Linux system version

This example will be used a downgrade from Ubuntu 20.10 to 20.04.

• From

  • Version: Ubuntu 20.10

  • Name: Gorilla Grovy

  • Codename: grovy

• To

  • Version: Ubuntu 20.04

  • Name: Focal Fossa

  • Codename: focal

Downgrade sources.list

sudo sed -i 's/groovy/focal/g' /etc/apt/sources.list

Pin packages

Open /etc/apt/preferences file and enter the following content while replacing the codename of the system codename you aim to downgrade to.

/etc/apt/preferences

Package: *
Pin: release a=focal v=20.04
Pin-Priority: 1001

Downgrade Ubuntu system

sudo apt update ; sudo apt upgrade ; sudo apt dist-upgrade

If you found any errors try this:

sudo apt --fix-broken install
sudo dpkg --configure -a
sudo apt dist-upgrade
sudo apt install ubuntu-desktop

Find and remove folder recursively

# Example: node_modules
  sudo find . -type d -name node_modules -exec rm -r {} \;

Open Mac External Harddrive on Linux

- [x] sudo apt-get install hfsprogs
- [x] Mount volume

or

- [x] chmod -R 777 /user/media/volumeX

# df -h
# sudo mount -t hfsplus -o remount,force,rw /dev/sdg1

Remote access using the xrdp package

apt install xrdp
adduser xrdp ssl-cert
systemctl restart xrdp

# Allow firewall access on port 3389
ufw allow 3389

# Change "allowed_users" to anybody
# like this: allowed_users=anybody
vim /etc/X11/Xwrapper.config


# Check your hostname
cat /etc/hostname

# Or get your ip address
if config

Install Postman

sudo apt update
sudo apt install snapd
sudo snap install postman

Unzip with the destination folder

Set -d parameter

unzip package.zip -d /opt

How to Install netstat Command in Linux

# [On CentOS/RHEL]
yum install net-tools     

# [On Debian/Ubuntu]
apt install net-tools     

# [On OpenSuse]
zypper install net-tools  

# [On Arch Linux]
pacman -S netstat-nat     

netstat -r -n

Show subnet

ip -o -f inet addr show | awk '/scope global/ {print $2, $4}'

Show gateway

ip route | grep default

User & Groups

Create new user

sudo adduser newuser

Add an existing user to the Sudo group

sudo usermod -aG sudo newuser

Bluetooth device disconnects right after connect

1. Remove the device on Pulse Audio Bluetooth Devices

2. Kill pulse audio and restart the Bluetooth service

sudo killall pulseaudio && sudo service bluetooth restart

Bash/Zsh undo (CTRL + Z)

Type: CTRL + /