Sendmail vs Mailx

• Sendmail → Mail Transfer Agent (MTA) responsible for routing and delivering email
• Mailx → Mail User Agent (MUA) used to compose and send messages from the command line

Install Sendmail

Ubuntu/Debian:

sudo apt-get update
sudo apt-get install sendmail
sudo sendmailconfig

CentOS/RHEL:

sudo yum update
sudo yum install sendmail sendmail-cf
sudo systemctl start sendmail
sudo systemctl enable sendmail

Install Mailx

Ubuntu/Debian:

sudo apt-get install mailutils

CentOS/RHEL:

sudo yum install mailx

Send Your First Email

Using Sendmail:

sendmail recipient@example.com < email.txt

Using Mailx:

echo "This is the body of the email" | mailx -s "Subject Here" recipient@example.com

Send Attachments with Mailx

Single attachment:

echo "Please find the attached report" | mailx -a ./report.pdf -s "Monthly Report" recipient@example.com

Multiple attachments:

echo "Please find the attached reports" | mailx -a ./report1.pdf -a ./report2.csv -s "Monthly Reports" recipient@example.com

Automate Email Delivery

Example:

echo "$body" | mailx -s "$subject" $recipient

Schedule with cron:

0 8 * * * /path/to/your_script.sh

This runs the script every day at 08:00.

Summary

• Sendmail handles routing and delivery
• Mailx simplifies email creation and attachments
• Supports automation through Bash scripts and cron
• Useful for reports, alerts, and system notifications

Full guide 👉 https://vsys.host/how-to/how-to-send-email-in-linux-from-the-command-line-with-sendmail-and-mailx

The free version includes access to more than 50 scripts, while the licensed version provides access to hundreds more.

Installing Softaculous in Plesk

For Plesk 12 and newer:

1. Log in to Plesk as root
2. Go to Server Management → Extensions
3. Open Extensions Catalog
4. Search for Softaculous
5. Click Install

After installation, Softaculous appears under My Extensions.

Verify ionCube Loader

Check whether ionCube is installed:

find / -name 'ioncube_loader_*' -exec grep -H 'ionCube PHP Loader' {} \;

Verify activation:

php -m | grep -i ioncube

Or check the version:

echo '<?php echo ioncube_loader_version(); ?>' > check_ioncube_version.php
php check_ioncube_version.php

Installing Softaculous via SSH

Connect as root and run:

wget -N http://files.softaculous.com/install.sh
chmod 755 install.sh
./install.sh

After installation, Softaculous becomes available in the control panel.

Installing Softaculous in cPanel/WHM

Before installation, enable ionCube Loader:

WHM → Server Configuration → Tweak Settings → PHP → ioncube

Then install Softaculous via SSH:

wget -N https://files.softaculous.com/install.sh
chmod 755 install.sh
./install.sh

After completion, access:

WHM → Plugins → Softaculous — Instant Installs

Summary

Softaculous simplifies application deployment in Plesk and cPanel.

Key steps:

• enable ionCube Loader
• install Softaculous from Extensions Catalog or via SSH
• manage applications directly from the control panel

Full guide 👉
https://vsys.host/how-to/how-to-installation-of-softaculous-in-plesk-and-cpanel

This guide covers how to configure IPv6 connectivity on a Linux server.

Why IPv6

Benefits include:

• larger address space
• improved routing efficiency
• direct end-to-end connectivity
• future-proof network infrastructure

Check Existing Network Configuration

Display current interfaces:

ip addr

or

ifconfig

Verify whether an IPv6 address is already assigned.

Configure IPv6 Address

Example:

ip -6 addr add IPV6_ADDRESS dev eth0

This assigns an IPv6 address to the selected network interface.

Configure Default Gateway

Example:

ip -6 route add default via IPV6_GATEWAY

Required for external IPv6 connectivity.

Verify Connectivity

Check routing:

ip -6 route

Test connectivity:

ping6 google.com

or

ping -6 google.com

Make Configuration Persistent

Depending on the distribution, IPv6 settings can be added to:

• /etc/network/interfaces
• Netplan configuration
• NetworkManager configuration

This ensures IPv6 remains active after reboot.

Summary

• assign IPv6 address
• configure IPv6 gateway
• verify routing and connectivity
• save configuration permanently

IPv6 support enables modern network connectivity and compatibility with IPv6-only services.

Full guide 👉 https://vsys.host/how-to/how-to-adding-ipv6-connectivity-to-your-server

This guide covers the basic workflow for mounting extra HDDs or SSDs in Linux systems.

Step 1 — Detect Disk

List available disks:

fdisk -l

or

lsblk

Used to identify the new device (e.g. /dev/sdb).

Step 2 — Create Partition

Open disk utility:

fdisk /dev/sdb

Typical flow:

• n → new partition
• w → write changes

Step 3 — Format Disk

Example (ext4):

mkfs.ext4 /dev/sdb1

Creates filesystem on the new partition.

Step 4 — Create Mount Point

mkdir /mnt/storage

Mount point = directory where the disk will be attached.

Step 5 — Mount Disk

mount /dev/sdb1 /mnt/storage

Verify:

df -h

Step 6 — Permanent Mount (fstab)

Get UUID:

blkid

Edit fstab:

nano /etc/fstab

Example:

UUID=xxxx /mnt/storage ext4 defaults 0 0

Ensures automatic mounting after reboot.

Summary

• detect disk → lsblk / fdisk -l
• partition → fdisk
• format → mkfs
• mount → mount
• persist → /etc/fstab

Full guide 👉 https://vsys.host/how-to/mounting-of-additional-hard-disks-in-linux

This is commonly used for:

• exposing internal services
• redirecting traffic to another port
• forwarding requests to another host

Enable IP Forwarding

Temporary:

echo 1 > /proc/sys/net/ipv4/ip_forward

Permanent:

sudo nano /etc/sysctl.conf

Set:

net.ipv4.ip_forward = 1

Apply:

sudo sysctl -p

Redirect Traffic to Another Port

Example:

iptables -t nat -A PREROUTING -p tcp --dport 80 \
-j REDIRECT --to-port 8080

Traffic from port 80 will be redirected to 8080.

Forward Traffic to Another Server

Example:

iptables -t nat -A PREROUTING -p tcp --dport 80 \
-j DNAT --to-destination 192.168.1.10:80

Used to forward traffic to another internal server.

Allow Forwarded Traffic

iptables -A FORWARD -p tcp -d 192.168.1.10 \
--dport 80 -j ACCEPT

Required to allow forwarded packets.

Configure NAT / Masquerading

iptables -t nat -A POSTROUTING -j MASQUERADE

Needed when forwarding traffic between networks.

Save Rules

Ubuntu / Debian:

sudo apt install iptables-persistent
sudo netfilter-persistent save

CentOS:

service iptables save

Verify Rules

iptables -L
iptables -t nat -L

Used to inspect forwarding and NAT rules.

Summary

• enable ip_forward
• use PREROUTING for redirects/DNAT
• allow traffic in FORWARD chain
• use MASQUERADE for NAT
• save rules for persistence

Full guide 👉
https://vsys.host/how-to/linux-port-forwarding-with-iptables

This guide covers RPM installation methods across different Linux distributions.

What is RPM

RPM packages contain:

• application files
• metadata
• dependencies
• installation scripts

Used for software installation and package management on RPM-based systems.

Install RPM on RHEL / CentOS / Rocky / AlmaLinux

Using yum:

sudo yum install package.rpm

Using dnf:

sudo dnf install package.rpm

dnf is the modern replacement for yum in newer distributions.

Install RPM on Fedora

sudo dnf install package.rpm

Fedora uses dnf by default.

Install RPM on openSUSE

sudo zypper install package.rpm

openSUSE uses the zypper package manager.

Install RPM Manually

Using RPM directly:

sudo rpm -ivh package.rpm

Options:

• -i → install
• -v → verbose
• -h → progress output

Upgrade RPM Package

sudo rpm -Uvh package.rpm

Used to upgrade existing packages.

Remove RPM Package

sudo rpm -e package_name

Removes installed RPM package.

Key Notes

• yum / dnf automatically resolve dependencies
• rpm alone does not resolve dependencies automatically
• package manager depends on distribution

Summary

• RHEL/CentOS → yum or dnf
• Fedora → dnf
• openSUSE → zypper
• rpm command → manual install/upgrade/remove

Full guide 👉
https://vsys.host/how-to/how-to-install-rpm-file-on-different-linux-distributions

Installation

• Download WinSCP from the official site
• Run installer and follow setup steps
• Optional: add features like PuTTYgen integration

Connection Setup

To connect:

• Host name → server IP or domain
• Port → depends on protocol
• Username + password

Default ports:

• SFTP → 22
• SCP → 22
• FTP → 20 / 21
• WebDAV → 80

File Transfer

• Local files → left panel
• Remote server → right panel
• Transfer via drag & drop

Authentication

• Supports password login
• Supports SSH key authentication via Advanced → Authentication settings

Security Notes

• Verify server fingerprint on first connection
• Avoid using root unless necessary
• Incorrect acceptance of warnings may lead to security risks

Summary

• GUI-based file transfer client
• Supports multiple protocols
• Drag & drop file operations
• SSH keys supported
• Requires correct host, port, credentials

Full guide 👉 https://vsys.host/how-to/data-transfer-with-winscp

This setup installs a graphical environment (XFCE4) and enables remote access via XRDP.

Requirements

• Linux system (Ubuntu / CentOS)
• Internet connection
• SSH or VNC access
• User with login privileges
• Basic terminal usage

Root login via GUI is not allowed — use a regular user with sudo.

Install GUI + XRDP

Ubuntu / Debian:

apt update
apt install xrdp vnc4server xubuntu-desktop

CentOS:

yum install -y epel-release
yum groupinstall "Server with GUI" -y
yum install -y xrdp tigervnc-server

XFCE4 is used as a lightweight desktop environment.

Configure and Run XRDP

• Install required packages
• Ensure network connectivity
• Start XRDP service
• Use a non-root user for login

Connect via RDP

• Use Remote Desktop client
• Enter server IP
• Authenticate with system user

Key Points

• GUI is optional but improves usability
• XFCE4 = lightweight and suitable for servers
• XRDP enables remote desktop access
• Works on existing servers (no reinstall required)

Summary

• Install GUI + XRDP packages
• Use XFCE4 for performance
• Connect via RDP client
• Avoid root login

Full guide 👉 https://vsys.host/how-to/how-to-install-a-gui-and-xrdp-on-ubuntu-and-centos

Ubuntu 20.04 supports both temporary and permanent hostname changes via CLI or GUI.

Check Current Hostname

hostname

hostnamectl

hostnamectl provides detailed system info including static, transient, and pretty hostnames.

Temporary Change (until reboot)

sudo hostname new-hostname

• applies instantly
• resets after reboot

Permanent Change (no reboot)

sudo hostnamectl set-hostname new-hostname

• applied immediately
• no reboot required

Permanent Change (with config files)

Edit:

sudo nano /etc/hostname

sudo nano /etc/hosts

Replace old hostname → new hostname.

Apply:

sudo systemctl reboot

Required for full system-level consistency.

Cloud Systems (Cloud-init)

Ensure persistence:

sudo nano /etc/cloud/cloud.cfg

Set:

preserve_hostname: true

Prevents hostname reset after reboot.

GUI Method

• Settings → About
• Change Device Name

Restrictions

• 1–63 characters
• alphanumeric + hyphens
• cannot start/end with hyphen

Summary

• temporary → hostname
• permanent → hostnamectl
• config files → /etc/hostname, /etc/hosts
• cloud → update cloud.cfg

Full guide 👉https://vsys.host/how-to/change-hostname-on-ubuntu-20-04

Rename a Single File (mv)

Basic syntax:

mv old_filename new_filename

Example:

mv file1.txt file2.txt

This renames a file without changing its location.

Rename Using Absolute Path

mv /path/old.txt /path/new.txt

Used when working outside the current directory.

Rename Multiple Files (mv + loop)

for f in *.txt; do
  mv -- "$f" "${f%.txt}.pdf"
done

Changes .txt → .pdf for all files in a directory.

Rename Multiple Files (rename)

rename 's/old/new/' *.txt

Example:

• replace text in filenames
• change extensions
• bulk rename

The rename command uses regex and is more flexible for batch operations.

Key Notes

• mv → simple rename (single file)
• rename → bulk rename with patterns
• loops → needed for batch operations with mv
• supports full paths and automation

Summary

• rename file → mv old new
• batch rename → rename or loops
• use regex for advanced patterns

Full guide 👉https://vsys.host/how-to/how-to-rename-files-in-linux