How to Install Telnet Server on CentOS/RHEL 6/5

Written by Gaurav | April 19, 2018

 CentOS, RHEL, Telnet 

Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. Using telnet server we can make a connection to a remote host using telnet client and get terminal.

Telnet server is not secured for remote access, that’s why we do not recommend to use Telnet server for login to remote server. To access Linux system remotely use ssh servers.

Install Telnet Server

Telnet server is available under default yum repositories. Execute following command to install it

# yum install telnet-server

Enable Telnet Service

Telnet is an xinetd based service, First edit telnet xinetd configuration file /etc/xinetd.d/telnet and set disable to no.

service telnet

{

        flags           = REUSE

        socket_type     = stream

        wait            = no

        user            = root

        server          = /usr/sbin/in.telnetd

        log_on_failure  += USERID

        disable         = no

}

Now restart xinetd service

# service xinetd restart

Connect to Telnet Server

Now connect to Telnet server using telnet client. For this example, we are connecting to Telnet server from windows host

c:> telnet svr1.infosolution.net

CentOS release 6.5 (Final)

Kernel 2.6.32-431.17.1.el6.i686 on an i686

login: Gaurav

Password:

Last login: Tue Apr 18 19:19:24 from 192.168.1.115

[Gaurav@svr1 ~]$

sshd start failed cause by "start sshd:/var/empty/sshd

sshd start failed cause by "start sshd:/var/empty/sshd must be owned by root and not gruop or world-writable"

Problem(Abstract)

sshd start failed cause by "start sshd:/var/empty/sshd must be owned by root and not group or world-writable" 

Cause

file dir /var/empty/sshd 's access permissions not been setup correct

Resolving the problem

Follow below instruction to do some change for access permissions of /var/empty/sshd

1) su - root

2) chmod 755 /var/empty/sshd

3) service sshd restart

Repair and optimise Database Tables in VICIdial and Goautodial

Repair and optimise Database Tables in VICIdial and Goautodial

It is an ideal practice to repair and optimize your vicidial database every 15 days or so. However, if you get any database crashes, these will be the issues to identify this crash.

• Session has been disabled
• Autodial calls not landing to the agents
• Realtime report not updating properly
• Agent Error / MySQL could not connect

Step 1: Login to SSH (use any SSH clients)

Step 2: Run this in the console.

mysqlcheck -u root -p –auto-repair –check –optimize –all-databases

It will ask your database password. Input the same and press enter. The repair will start and take a minute or two to finish. After it is done, reboot the server.

• Default database password for Goautodial is “vicidialnow” without quotes.

Recommended: Make sure you keep power backup for your VICIdial server if that is hosted in your office premises. The sudden power loss to the server creates database crashes very often.

TCP/IP Protocal Stack

What is encapsulation?TCP/IP Protocal Stack?

Each layer adds a header and a trailer send to the another layer.
Trailer is Error checking methods

One person Writing data in his own PC.
He likes to send file to destination , In Between how it works

Here We going to explain How TCP/IP Works

What actually happens IF the files passes through TCP/IP .

TCP/ IP Protocal consist of
-Applicaion
-Transport layer
-Internet
-Network access layer.

Step 1
Application Layer(DATA)-->Assume that you have Big DATa . One DATA you can't send in one single shot.
What it will do ,

Here Application Part over

Step 2

Transport Layer --->It will segerate as a segment after that sequene wise one by one will send.

Segment - Segregated
Sequence-> First , Second , Third
Port number - This Data should go through this ID

Here Tansport part over

Step 3

Internet Layer

All There things merge in Transport Header--->Begining of the information

Assume segement , sequence and port num in the courier cover .
Sequence --->In that courier cover we need address, that mean Sequence need to know source and destination IP
also we required Who sends it ---> Source IP Address
Who received it --> Destination IP Address

Here we knows how to that get to that district->Network , How do that get to that building -->IP address---> Here involves Router

Step 4

Network access layer -MAC Address

Here you are sending to the building suppose you need to send to the particular person mean,
you required Source and Destination MAC Address--Here involves switch.

Trailer is the end of the information

In that courier has 100 pages, whether same pages destination person received or not , Here error checksome is coming to the picture.

Courier everythig filled up , now going to post in postel box . Small truck will come and take it up --->Here Framerelay involves
Framerelay knows where the data should go.

Step 5
Phsical Layer

Here Truck should go in road right ? That's what Ethernet cable involves here
Also we can send courier to Aeroplane too , that's what Fibre cable involves here

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