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How to add directory to PATH in Linux

The $PATH environment variable is a list of directories that tells the shell which directories to search for executable files.

To check what directories are in your $PATH list use command:

echo $PATH

To add new directory ~/.local/bin/ to $PATH use command:

export PATH="$HOME/.local/bin:$PATH"

But this change is only temporary and valid only in the current shell session.

To make the change permanent, you need to define the $PATH variable in the shell configuration files. In most Linux distributions when you start a new session, environment variables are read from the following files:

Global shell specific configuration files such as /etc/environment and /etc/profile. Use this file if you want the new directory to be added to all system users $PATH.
Per-user shell specific configuration files. For example, if you are using Bash, you can set the $PATH variable in the ~/.bashrc file. If you are using Zsh the file name is ~/.zshrc.

In this example, we’ll set the variable in the ~/.bashrc file. Open the file with your text editor and add the following line at the end of it:

nano ~/.bashrc

export PATH="$HOME/.local/bin:$PATH"

Save the file and load the new $PATH into the current shell session using the source command:

source ~/.bashrc

To confirm that the directory was successfully added, print the value of your $PATH by typing:

echo $PATH

Yt-dlp: youtube-dl alternative

yt-dlp is a youtube-dl fork based on the now inactive youtube-dlc. The main focus of this project is adding new features and patches while also keeping up to date with the original project.

Official GitHub repository: https://github.com/yt-dlp/yt-dlp

Installation:

sudo wget https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp -O /usr/local/bin/yt-dlp
sudo chmod a+rx /usr/local/bin/yt-dlp

Yt-dlp usage similar as a youtube-dl. To show all supported video formats use command:

yt-dlp -F https://youtube.com/video-id

To download video use command with flag yt-dlp -f <firmat-id> <video-url>

yt-dlp -f 22 https://youtube.com/video-id

To download all videos from playlist and convert them to mp3 use command:

yt-dlp --ignore-errors --format bestaudio --extract-audio --audio-format mp3 --audio-quality 160K --output "%(title)s.%(ext)s" --yes-playlist 'YOUTUBE-PLAYLIST-URL'

Install Proxmox VE on Debian

Proxmox VE (Proxmox Virtual Environment) – this is a open source virtualization system, that uses a hypervisor KVM and LXC, based on Debian GNU Linux.

First edit your /etc/hosts file and write there your IP address:

sudo nano /etc/hosts

192.168.1.2    hostname.com   hostname

Add Proxmox VE distribution to your operating system:

echo "deb http://download.proxmox.com/debian/pve buster pve-no-subscription" > /etc/apt/sources.list.d/pve-install-repo.list

Add key for Proxmox VE repository:

wget http://download.proxmox.com/debian/proxmox-ve-release-6.x.gpg -O /etc/apt/trusted.gpg.d/proxmox-ve-release-6.x.gpg
chmod +r /etc/apt/trusted.gpg.d/proxmox-ve-release-6.x.gpg # optional, if you have a non-default umask

Update packages list and upgrade your system:

apt update && apt full-upgrade

Install Proxmox VE packages:

apt install proxmox-ve postfix open-iscsi

Reboot your system

reboot

After reboot open your web borwser and go to https://192.168.1.2:8006, where 192.168.1.2 – is a IP address of your Proxmox computer, and 8006 – default Proxmox port.

That’s all, Proxmox VE successfully installed on your PC. Now you can create new Virtual machines…

Bdcom P3310 delete, block and unblock ONU

To delete OUN from OLT on EPON 2 interface go to config and use interface EPON0/2:

enable
config
interface EPON0/2

To delete ONU use command (note, that adter delete ONU will register on OLT again):

no epon bind-onu mac e067.b37d.d3d3

To add ONU to Black List use command:

epon onu-blacklist mac e067.b37d.d3d3

To remove ONU from Black List use command:

no epon onu-blacklist mac e067.b37d.d3d3

Best and simplest Mikrotik Firewall rules

Don’t forget to update your Mikrotik firmware to 6.41.1 or higher! Current stable and secure firmware is 6.47.10.
Simple Mikrotik Firewall configuration:

In Mikrotik terminal go to Firewall Filter:

/ip firewall filter

For increase the speed of router fist rule should be:

add chain=forward action=fasttrack-connection connection-state=established,related

Allow Established and Related connections for forward and input chains:

add chain=forward action=accept connection-state=established,related,untracked log=no log-prefix=""
add chain=input action=accept connection-state=established,related,untracked log=no log-prefix=""

Drop invalid connections for forward and input chains only from WAN interfaces:

add chain=forward action=drop connection-state=invalid in-interface-list=WAN log=no log-prefix=""
add chain=input action=drop connection-state=invalid in-interface-list=WAN log=no log-prefix=""

Allow ICMP ping from WAN only width 128 bits packets:

add chain=input action=accept protocol=icmp in-interface-list=WAN packet-size=0-128 log=no log-prefix=""

Allow remote control by Winbox or SSH only from IP addresses from AccessList:

add chain=input action=accept protocol=tcp src-address-list=AccessList in-interface-list=WAN dst-port=8291,22 log=no log-prefix=""

In IP -> Firewall -> Address List create new address list width name AccessList and add there all IP addresses you want to use for remote connection to your router.

Allow OpenVPN connections:

add chain=input action=accept protocol=tcp in-interface-list=WAN dst-port=1194 log=no log-prefix=""

Allow PPTP VPN connections:

add chain=input action=accept protocol=tcp in-interface-list=WAN dst-port=1723 log=no log-prefix=""
add chain=input action=accept protocol=gre log=no

Allow SSTP VPN connection (443 port,
change port if yout SSTP server run on other port):

add chain=input action=accept protocol=tcp in-interface-list=WAN dst-port=443 log=no log-prefix=""

Allow L2TP IPsec VPN connection:

add action=accept chain=input in-interface-list=WAN protocol=ipsec-esp comment="allow L2TP VPN (ipsec-esp)"
add action=accept chain=input dst-port=500,1701,4500 in-interface-list=WAN protocol=udp comment="allow L2TP VPN (500,4500,1701/udp)"

Drop all other connections to Mikrotik and to local network:

add chain=input action=drop in-interface-list=WAN log=no log-prefix=""
add chain=forward action=drop connection-nat-state=!dstnat in-interface-list=WAN log=no log-prefix=""

In IP -> Services menu enable only SSH and Winbox services, for more security you can change default Winbox and SSH ports:

It is all you need to secure your home or office router and network.

Don’t forget to update your Mikrotik firmware to 6.41.1 or higher! Current stable and secure firmware is 6.48.6. For more stability use firmware from “long term” channel.

How to auto start program in Linux with root privilegies

To run some script or program when computer start in linux – copy this program to /etc/init.d directory. Change permissions to 755.

For example let’s create simple bash script “ntpsync“that sync system clock with NTP server in Internet:

service ntp stop
ntpdate time.nist.gov
service ntp start

Copy this sctipt to /etc/init.d, create symbolic link to /etc/rc3.d:

ln -s /etc/init.d/ntpsync /etc/rc3.d/ntpsync

Rc3 level – Мulti-user regime width network support.

That’s all, on next startup Linux will run this script, and automatically sync system clock with NTP server from Internet.

Python Lesson 2 (Variables and types)

Python is completely object oriented, and not “statically typed”. You do not need to declare variables before using them, or declare their type. Every variable in Python is an object.

Numbers

Python supports two types of numbers – integers(whole numbers) and floating point numbers(decimals).

myint = 7
print(myint) # Print integer 7

myfloat = 7.0
print(myfloat) # Print float 7.0

myfloat = float(7)
print(myfloat) # Print float 7.0

Strings

Strings are defined either with a single quote or a double quotes.

mystring = 'hello'
print(mystring)

mystring = "hello"
print(mystring)

Assignment of variables

first = sec = third = 1 # All three variables will be assigned 1
first, sec, third = "Hi", 75, 23.1 # Variables will be assigned in turn

To assign variable value from keyboard use command:

# String from keyboard will be assigned to variable first_var
first_var = input("Enter text: ")

Change type of variable:

int_var = int(input("Enter integer number: "))
float_var = float(input("Enter float number: "))
str_var = str(input("Enter integer number: "))

float_var = float(int_var) # Convert int to float
int_var = int(float_var) + int(float_var) # Convert float to int
str_var = str(25) # Convert number 25 to string

If you try to convert string to number you will get error.

You can do arithmetic operations width variables

# Assign integer value 10 to variable int_var
int_var = int(5.0) + int(5.0) 

# Add 2 to int_var
int_var += 2

# Multiply string
str_var = 'Test'
str_var *= 5 # assing string 'TestTestTestTestTest'

Python Lesson 1 (Hello World):

Python is a very simple language, and has a very straightforward syntax. The simplest directive in Python is the “print” directive. In our first lesson we create script hello.py that write phrase “Hello World“.

print("Hello World\n")

Symbol \n used to set cursor on new line. That’s all it is let’s start our script:

python3 hello.py

And we will see phrase “Hello World” on our display.

Download video from YouTube and convert it to mp3 in Linux

To download video from YouTube you can use some site in Internet, but many of them have ads, viruses and don’t do what you need.

But you can use simple program youtube-dl. It is free, open source, work in console and can download video, audio from YouTube in one click.

To install youtube-dl use simple commands:

1. Install python:

sudo apt install python3
sudo ln -s /usr/bin/python3 /usr/local/bin/python

2. Install youtube-dl:

sudo wget https://yt-dl.org/downloads/latest/youtube-dl -O /usr/local/bin/youtube-dl
sudo chmod a+rx /usr/local/bin/youtube-dl

How to use youtube-dl:

To get all supported formats from YouTube video use command:

youtube-dl -F https://www.youtube.com/watch?v=QpqdtB4ssX0

Thic sommand show you all video formats and id’s

To download some format use flag -f and ID from previous command:

youtube-dl -f 18 https://www.youtube.com/watch?v=QpqdtB4ssX0

That’s all, video starts download. You can use it in terminal and don’t need to open suspicious sites.

You can also download playlists of video from YouTube the same way.

Convert video to mp3 audio.

And you can convert video to mp3 using program ffmpeg. To install ffmpeg use command:

sudo apt install ffmpeg

To convert video to mp3 use command:

ffmpeg -i video.mp4 -acodec libmp3lame audio.mp3

How to Enable Auto Login in Windows 10

To enable automatic login in Windows 10 use program netplwiz. Open Run command line (Win+R) and enter command netplwiz:

In next window uncheck option “User must enter a user name and password to use this computer.”

Enter password from your Windows 10 account and reboot computer.