Basic linux commands on Ubuntu 22.04

Sudoers

Add NOPASSWD

This section modifies the sudoers file to allow specific users to execute commands with sudo privileges without entering a password.

sudo nano /etc/sudoers.d/ubuntu

ubuntu ALL=(ALL) NOPASSWD:ALL

Add commands

This section adds another entry to the sudoers file, but this time for the deploy user and specifies a list of allowed commands.

sudo nano /etc/sudoers.d/deploy

deploy ALL=(ALL) NOPASSWD: /bin/mv, /bin/sed, /bin/rm, /bin/chmod, /bin/chown, /home/deploy/scripts/deploy.sh

Create SSH file and folder

This section sets up SSH for the deploy user by creating the necessary file and directory structure. It includes the following commands:

sudo adduser --disabled-password deploy
mkdir /home/deploy/.ssh
chmod 700 /home/deploy/.ssh
touch /home/deploy/.ssh/authorized_keys
chown deploy:deploy /home/deploy/.ssh/authorized_keys
chmod 600 /home/deploy/.ssh/authorized_keys

Firewall : ufw -> deny incoming, allow outgoing, ssh, http, https

This section configures the Uncomplicated Firewall (UFW) to control incoming and outgoing network traffic.

sudo apt install ufw -y
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow 3222
sudo ufw allow http
sudo ufw allow https
sudo ufw enable

These commands help to secure the system by restricting incoming connections and allowing only specific ports.

Timezone : Europe/Brussels

This section sets the system’s timezone to “Europe/Brussels”.

sudo timedatectl set-timezone Europe/Brussels

unattended-upgrades :

This section installs and configures the unattended-upgrades package, which automatically applies security updates to the system.

sudo apt install unattended-upgrades -y
sudo dpkg-reconfigure -plow unattended-upgrades

Quit command:

sudo apt install unattended-upgrades -y
sudo dpkg-reconfigure -f noninteractive unattended-upgrades

The package allows for automatic security updates, reducing the risk of vulnerabilities.

Update welcome message

This section modifies the MOTD (Message of the Day) to display a custom welcome message.

sudo nano /etc/update-motd.d/99-custom-welcome

#!/bin/sh

echo "██████  ██████   ██████  ██████  ██    ██  ██████ ████████ ██  ██████  ███    ██ "
echo "██   ██ ██   ██ ██    ██ ██   ██ ██    ██ ██         ██    ██ ██    ██ ████   ██ "
echo "██████  ██████  ██    ██ ██   ██ ██    ██ ██         ██    ██ ██    ██ ██ ██  ██ "
echo "██      ██   ██ ██    ██ ██   ██ ██    ██ ██         ██    ██ ██    ██ ██  ██ ██ "
echo "██      ██   ██  ██████  ██████   ██████   ██████    ██    ██  ██████  ██   ████ "
echo ""
echo ""

#!/bin/sh

echo " ██████ ███████ ██████  ████████ ██ ███████ ██  ██████  █████  ████████ ██  ██████  ███    ██ "
echo "██      ██      ██   ██    ██    ██ ██      ██ ██      ██   ██    ██    ██ ██    ██ ████   ██ "
echo "██      █████   ██████     ██    ██ █████   ██ ██      ███████    ██    ██ ██    ██ ██ ██  ██ "
echo "██      ██      ██   ██    ██    ██ ██      ██ ██      ██   ██    ██    ██ ██    ██ ██  ██ ██ "
echo " ██████ ███████ ██   ██    ██    ██ ██      ██  ██████ ██   ██    ██    ██  ██████  ██   ████ "
echo ""
echo ""

#!/bin/sh

echo "██████  ███████ ██    ██ "
echo "██   ██ ██      ██    ██ "
echo "██   ██ █████   ██    ██ "
echo "██   ██ ██       ██  ██  "
echo "██████  ███████   ████   "
echo ""
echo ""

sudo chmod +x /etc/update-motd.d/99-custom-welcome

These modifications customize the welcome message displayed when logging into the system.