How to Build Your Own Amazon Echo with a Raspberry Pi

As you'd expect, you'll need a Raspberry Pi alongside a handful of parts:

A Raspberry Pi 3 (recommended) or Raspberry Pi 2 (you'll also need a USB Wi-FI adapter with the Model 2) with Raspbian installed. If you haven't installed Raspbian before, our guide covers everything you need to know.
A MicroUSB power cable
An 8GB MicroSD card
A USB Microphone (I used this cheap $6 mic, but pretty much any USB mic seems to work. The $8 Playstation Eye seems to work especially well if you're looking for a slight upgrade)
Speakers (any powered speaker does the job, I decided to use a UE Mini Boom because I already owned it and even when it's plugged into the Pi, it still works as a Bluetooth speaker)
A Keyboard and Mouse for setup (or access to a computer with VNC)

Enabling VNC Server

On your Raspberry Pi, run the following commands to make sure you have the latest version of VNC Connect:

sudo apt-get update
sudo apt-get install realvnc-vnc-server realvnc-vnc-viewer

Now enable VNC Server. You can do this graphically or at the command line.

Cacti tool is an open source web based network monitoring and system monitoring graphing solution for IT business. Cacti enables a user to poll services at regular intervals to create graphs on resulting data using RRDtool. Generally, it is used to graph time-series data of metrics such as network bandwidth utilization, CPU load, running processes, disk space etc.

In this how-to we are going to show you how to install and setup complete network monitoring application called Cacti using Net-SNMP tool on RHEL 6.x and CentOS 6.xsystems using YUM  package manager tool.

Cacti Required Packages

The Cacti required following packages to be installed on your Linux operating systems like RHEL / CentOS

1. Apache : A Web server to display network graphs created by PHP and RRDTool.
2. MySQL : A Database server to store cacti information.
3. PHP : A script module to create graphs using RRDTool.
4. PHP-SNMP : A PHP extension for SNMP to access data.
5. NET-SNMP : A SNMP (Simple Network Management Protocol) is used to manage network.
6. RRDTool : A database tool to manage and retrieve time series data like CPU load, Network Bandwidth etc.

Installation
yum install telnet telnet-server -y
vi /etc/xinetd.d/telnet

Set disable = no:

# default: on
# description: The telnet server serves telnet sessions; it uses \
#       unencrypted username/password pairs for authentication.
service telnet

A. You can migrate users from old Linux server to new Linux sever with standard commands such as tar, awk, scp and others. This is also useful if you are using old Linux distribution such as Redhat 9 or Debian 2.x.

Following files/dirs are required for traditional Linux user management:
* /etc/passwd – contains various pieces of information for each user account

* /etc/shadow – contains the encrypted password information for user’s accounts and optional the password aging information.

* /etc/group – defines the groups to which users belong

* /etc/gshadow – group shadow file (contains the encrypted password for group)

* /var/spool/mail – Generally user emails are stored here.

* /home – All Users data is stored here.