Tài liệu Configuring Telnet in Linux ppt

Lab 10.4.5: Configuring Telnet in Linux Estimated Time: 25 Minutes Objective In this lab, the student will learn how to configure Telnet services on a system so that the user can remot

Lab 10.4.5: Configuring Telnet in Linux

Estimated Time: 25 Minutes

Objective

In this lab, the student will learn how to configure Telnet services on a system so that the user can remotely administer a Linux server

Equipment

The following equipment is required for this exercise:

• A system running Linux Red Hat 7.2 or greater

• Another system, either Linux or Windows, to attempt to Telnet into the Linux server

Scenario

The student is setting up a Linux server that will need to be administered and accessed remotely To do this, Telnet services will be installed on the Linux Red Hat 7.2 computer

Procedures

In Linux Red Hat 7.2, the Telnet services are not started by default In this lab, the

student will first have to navigate to the configuration file to start the Telnet services Second, the student will need to make sure that the proper accounts are created to access the server through Telnet In the last part of the lab, the student will test the Telnet services to confirm that the Telnet services are properly installed and started on the server

Step 1: Configuring Telnet Services

1 Login with the root account Make sure to be at the CLI command prompt If in the KDE interface, open up a terminal emulator window

2 From a terminal windows, type:

cd/etc/xinetd.d

This will change the user to the directory where the Telnet configuration file is

located

3 Next, type:

ls

This will display a list of all the configuration files in the xinetd.d directory

Example of the /etc/xinetd.d directory

4 Locate the Telnet file Is it present? Y/N

5 Next, check the confirmation of the Telnet file:

vi telnet

This will allow the user to use the vi Editor to change the Telnet configuration file

6 Once the vi Editor window opens, press i on the keyboard to enter “insert” mode Locate the “disable = yes” line in the configuration file Use the arrow keys on the

keyboard to move the cursor to delete the word “yes” and replace it with “no” This will change the configuration file to allow Telnet access to the server

Step 2: Starting the Telnet xinetd Daemon

1 Before testing the Telnet service, make sure that the Telnet daemon is running The daemon that runs the Telnet services is called xinetd (the same daemon that worked with FTP) From the command prompt, type:

/etc/rc.d/init.d/xinetd stop

2 Next, start the xinetd daemon:

/etc/rc.d/init.d/xinetd start

3 Check the status of the xinetd daemon:

/etc/rc.d/init.d/xinetd status

In the space below, write down the status of the xinetd daemon?

Step 3: Testing Telnet Access to the Localhost

1 To test Telnet services, type:

telnet localhost

This will use the system to access the Telnet services on the system

At this point the system will attempt to make a Telnet to the system through the local loopback address, 127.0.0.1 It will run through the login procedure and prompt the user to enter a username and password

2 A user cannot login to a remote site with the root account Use one of the other student accounts to log on and test the Telnet configuration

If a connection to the system is established, then the Linux server has been

successfully configured for Telnet access

What directory are you in? To find out, type:

pwd

In the space below, write down the current working directory:

_ _

Example of a Telnet session to the localhost and running the pwd command

Step 4: Connecting to Other Systems via Telnet (optional)

1 As in the FTP lab, use the ifconfig command to get an IP address Exchange IP addresses with a classmate

2 Telnet to their computer and have them Telnet to the one being used Telnet cannot

be used with the root account, so use a student account created in previous labs

3 The student can also use a MS Windows computer to Telnet to a Linux computer The example below shows the output of the command line in a windows computer

To Telnet from a Windows computer, go to the run command and type Telnet and the IP address

When prompted, type in the correct user account and password

Troubleshooting

Configuring services like Telnet for a Linux operating system can be somewhat confusing

to the inexperienced user Editing the configuration files can be a difficult task, so it is

important to remember where these files are located and how to navigate to them Telnet

can be a useful troubleshooting tool, which will allow access to the system from virtually

any operating system that has an Internet connection As a system administrator, this can

help with troubleshooting efforts

Reflection

1 What security risks does enabling Telnet pose to a system?

2 What are some precautions that would allow a users to provide security while having

Telnet access enabled on a system?