Look status:

# systemctl status firewall

# firewall-cmd --state

running

View zones:

# firewall-cmd –list-all

public (active)

target: default

icmp-block-inversion: no

interfaces: eth0

sources:

services: dhcpv6-client ssh

ports: 8081/tcp 53/udp 53/tcp

protocols:

masquerade: no

forward-ports:

source-ports:

icmp-blocks:

rich rules:

It is seen that the open service: ssh (22/TCP),dhcpv6-client and ports 8081/tcp 53/udp 53/tcp, a Protocol is required without this the command will not be accepted

Allow connection to a specific port (for example 1732 ) is very simple:

# firewall-cmd --add-port=1732/tcp

# firewall-cmd --runtime-to-permanent

The second command will overwrite the Active settings to the saved and agreeme at boot

To remove a port from the rules, use the –remove-port parameter:

# firewall-cmd --remove-port=1732/tcp

# firewall-cmd --runtime-to-permanent

In General, many –add-* commands have values for checking the status of –query-*, –list-* — list, changing –change -*, or deleting –remove the corresponding value. For brevity, we will not continue to focus on this. After reload rules check:

# firewall-cmd --list-ports

Firewalld provides a mode that allows you to block all connections with a single command:

# firewall-cmd --panic-on

To check which mode the firewall is in, there is a special key:

# firewall-cmd --query-panic

Panic mode is disabled:

# firewall-cmd --panic-off

It is not necessary to know which port is associated with the service in firewalld, just specify the name of the service. The utility will take care of the rest. After installing firewall knows the settings of more than 50 services, we get a list of them.

# firewall-cmd --get-services

Allow http connection:

# firewall-cmd --add-service=http

Using braces, you can specify multiple services at once. Information on the settings of the services available through

# firewall-cmd --info-ser

Debian

One of the most universally compatible Linux distributions. it is long-term in support and the very first distribution. It has a graphical shell GHOME. From its advantages can be distinguished

• The presence of a modern Linux kernel
• Extra large package storage
• Big Tracking System
• Great support for architectures (x86, x64, ARM)

CentOS

Every third user of Linux will select this operating system. Absolutely all software products designed for work and support of the Linux environment will work in CentOS.

• Ensuring installation in UEFI Secure Boot mode on supported hardware
• Very easy transition to systemd, firewalld and GRUB2
• Very reliable server solution

Ubuntu

This operating system is the best solution for openStack public clouds. Today, many users for their personal computers use this particular operating system. The main advantages can be distinguished

• This operating system can always be easily downloaded, use is very simple, and configurations are easy
• It is one of the safest operating systems due to the fact that it has a built-in firewall and anti-virus software
• It is interesting that Ubuntu has been translated into more than 50 languages ​​of the world, and is available to many users
• In support of servers, Ubuntu is one of the most popular systems, because of its simplicity, reliability and security systems

FreeBSD

This distribution includes a security group that controls all of this software. A wide selection of additional applications and programs is installed by pkg packages or by compiling code. The main advantages can be distinguished

• Due to licensing, much of FreeBSD, the coded has become an integral part of other operating systems, such as Apple, and the Sony’s PlayStation software system
• FreeBSD has a large set of server software in the base system and a set of ports. This allows you to configure FreeBSD and use it as a mail server, web server, firewall, FTP server, DNS server and router, as well as other applications

KernelCare

KernelCare – the great option for hosting provaiders and businesses. KernelCare runs on Ubuntu, CentOS, Debian, and other popular flavors of Linux. It checks for updates every 4 hours and installs them automatically. Patches can be rolled back. KernelCare is free for nonprofits. To install KernelCare, run the installation script:

wget -qq -O - https://kernelcare.com/installer | bash

If you are using an IP based license, nothing else is required. Otherwise, if you are using a key based license, run the following command to register the service:

/usr/bin/kcarectl --register <your-key>

Where is the registration code string <your-key>provided when signing up for a trial or purchasing a product. You can get it on this page. Below are some useful KernelCare commands. To check if a running KernelCare kernel is supported:

curl -s -L https://kernelcare.com/checker | python

To unregister a server:

sudo kcarectl --unregister

To check the status of the service:

sudo kcarectl --info

The software will automatically check for new patches every 4 hours. To update manually, run:

/usr/bin/kcarectl --update

Canonical Livepatch

Canonical Livepatch is a service that fixes a running kernel without rebooting your Ubuntu system. Livepatch is free to use on three Ubuntu systems. To use this service on more than three computers, you need to subscribe to the Ubuntu Advantage program. Before installing the service, you need to get a livepatch token from the Livepatch service website. After installing the token and enabling the service by running the following two commands:

sudo snap install canonical-livepatch
sudo canonical-livepatch enable <your-key>

To check the status of the service, run:

sudo canonical-livepatch status --verbose

Later, if you want to unregister the machine, use this command:

sudo canonical-livepatch disable <your-key>

The same instructions apply for Ubuntu 20.04 and Ubuntu 18.04.

In the Debian distribution, the root user can only connect using the keys and cannot connect using the password. The configuration file itself may contain settings that may be useful to you depending on the situation. Keys DennyUsers and AllowUsers – Allows you to restrict users and IP from which they can connect. For example, these lines:

DennyUsers login
AllowUsers "root@15.45.78.5,johnn,anny@78.65.55.0/24"

Only root, johnn, anny users can connect. In addition, the root user can only connect with IP 15.45.78.5 and anyy from the 78.65.55.0/24 subnet.

Key Match – Let’s redefine some settings and global restrictions for connections that fall under the filter.

For example:

PasswordAuthentication no
PermitRootLogin no
Match Address 1.2.3.4,9.8.7.6 Host vps12.hostry.com
PasswordAuthentication Yes
PermitRootLogin yes

For connections from addresses 1.2.3.4,9.8.7.6 and from the node vps12.hostry.com will allow you to use a password

X11Forwarding no
Match User John Address 172.16.1.*
X11Forwarding yes

Add a New User Account

To create a user account, you need to use the adduser command. We recommend using a strong password for the user! An example of a strong password is aoQ7w52!OKvA$Pfz. Next, you can enter values ​​for user information, or press ENTER to leave these fields blank.

# adduser example_user
Adding user `example_user' ...
Adding new group `example_user' (1001) ...
Adding new user `example_user' (1001) with group `example_user' ...
Creating home directory `/home/example_user' ...
Copying files from `/etc/skel' ...
New password:
Retype new password:
passwd: password updated successfully
Changing the user information for example_user
Enter the new value, or press ENTER for the default
        Full Name []: Example User
        Room Number []:
        Work Phone []:
        Home Phone []:
        Other []:
Is the information correct? [Y/n] y

Add User to Sudo Group

You can add a new user to the sudo group using the usermod command

# usermod -aG sudo example_user

Test

Switch to a New user

# su - example_user

Make sure you are the new whoami user, then test sudo access with sudo whoami which should return root

$ whoami
example_user
$ sudo whoami
[sudo] password for example_user:
root

Done!

Linux presents opportunities to work on this platform. They are very numerous, and many of them have been added since their initial release.

Some features will be presented below:

• CAP_KILL: Bypassing permission checks for sending signals to processes
• CAP_SYS_NICE: Enhance the nobility of processes (an explanation of the nobility can be found here)
• CAP_DAC_OVERRIDE: Override discretionary access control, For example, vto bypass the read / write / execute permissions check.

If you enter in the terminal “man 7 capabilities” then more additions and entries will appear

We also want to introduce a list of supported hardware called “Linux Hardware Howto” http://www.ibiblio.org/mdw/%20HOWTO%20/%20Hardware-HOWTO.html

Regarding graphic of programs in this system, there are a lot of them! From simple to powerful editors. We provide the 42 best programs, but in fact, there are many more! http://www.linuxlinks.com/GraphicsSoftware/

To view the contents in your file, you must enter:

less your-file-name

To see line numbers in each line, use the –N option:

less -N your-file-name

Less Keyboard Navigation

There are several techniques for checking open ports and processes running on your Ubuntu. You can use netstat and grep commands

Grep & Netstat

The netstat command gives you the ability to display network status and protocol statistics on your server. Netstat displays different types of network data depending on the command line parameter used. TCP and UDP endpoints can be seen in tables, routing tables, and interface information formats. The Grep command parses the file and displays each line that contains this pattern for a specific character pattern.

In order to use the netstat command, you can enter the following command, which is listed below (check the http port):

netstat -ltnp | grep -w ': 80'

It is also possible to list all listening TCP or UDP ports, including those using ports and socket state. To do this, you need to enter a very simple but useful command such as:

netstat -tunlp

Using SS

The ss command is a special tool that is configured to use the display of network socket information on a Linux system. The tool displays more detailed information than the netstat command, which is used to display active socket connections.

Lscpu Command

lscpu is a very handy and simple program that allows you to get all the information you need regarding Linux processor architecture. Login to your terminal and enter the following command:

lscpu

The Architecture field shows what type of CPU you have. Here x86_64 stands for 64-bit. CPU operation mode – 32-bit and 64-bit. This means your processor supports both 32-bit and 64-bit instructions.

Uname Command

Uname provides information about your Linux system and kernel version. Run the following command to get CPU information using the uname command. This can be done as follows:

uname -m

If you have a 64-bit system, then the output will be as follows:

x86_64

Lshw Command

Lshw is a simple command to display information about the hardware of your Linux system. You can get information about the Linux processor by running the following command:

lshw -c cpu

The output will be as follows:

A graphical interface is a kind of unique opportunity for simple work and management of all files and multimedia. It is very convenient to use it, because it can be used by people with any skills: both with beginners and technically advanced.

This interface allows the user to interact with electronic devices using graphic icons.

Using the GUI, you have access to a unique and very understandable way to navigate and interact with the computer. Also, the graphical interface allows you to simplify the creation of websites without skills in the field of HTML, CSS, JavaScript

Installing GUI on Linux

To install the graphical user interface on the Linux operating system, you need the following actions:

Go to the list of your services: https://hostry.com/orders/  and select the desired virtual server where you want to install the GUI. If you do not have a server, you can order it right now by clicking on the link: https://hostry.com/products/vps/

You need connect to your VPS – by following this links below:

It is necessary to log in and register the following commands:

UBUNTU

apt update
apt install xfce4
start

DEBIAN

apt-get update
apt-get install xfce4 -y
apt-get install xfce4-goodies -y

CENTOS

yum update 
yum -y group install "CNOME Desktop" "Graphical Administration Tools" 
ln -sf /lib/systemd/system/runlevel5.target /etc/systemd/system/default.target 

After successful installation, you will have a GUI panel, where you can quickly and easily manage your data from a computer!

For ubuntu and debian

For centos