Configure and use Telnet in RedHat Linux 9

Configure and use Telnet in RedHat Linux 9

To configure the telnet service, follow these steps:

　　1. Install the Telnet package (usually two)

1. telnet-client (or telnet). This package provides the Telnet client program;

2. telnet-server. This package provides telnet server programs;

Check whether these software packages are installed before installation. The method is as follows:

[Root @ wljs root] # rpm-Q telnet or [root @ wljs root] # rpm-Q telnet-Client [Root @ wljs root] # rpm-Q telnet-Server

If no software package is detected, install it. By default, the Telnet software package is installed in Red Hat Linux 9. Generally, you only need to install the telnet-server software package.

1. Get the telnet-server-0.17-25.i386.rpm package from the installation disk of Red Hat Linux 9.

2. install the software package

[Root @ wljs root] # rpm-I telnet-server-0.17-25.i386.rpm

　　Ii. Start the Telnet Service

1. Start the service

Method 1: Use ntsysv to add * Before Telnet in the displayed window, and then press OK.

Method 2: edit/etc/xinetd. d/telnet

[Root @ wljs root] # vi/etc/xinetd. d/telnet

Find disable = yes and change Yes to No.

2. Activate the service

[Root @ wljs root] # service xinetd restart

　　Iii. Test services

[Root @ wljs root] # telnet IP (or hostname)

If the configuration is correct, the system prompts you to enter the user name and password of the remote machine.

Login: Password:

Note: Only common users are allowed by default.

　　4. Set the telnet port

# Vi/etc/services

Go to edit mode and find telnet (input/telnet in VI editing mode)

The following content is found:

Telnet 23/tcp Telnet 23/udp

Modify 23 to an unused port number (for example, 2000), exit VI, restart the telnet service, and modify the default port number for telnet.

　　V. Telnet service restrictions

Telnet is a plaintext transmission password and data. If you are not satisfied with the default settings, You need to restrict the service scope. Suppose your host's IP address is 210.45.160.17, you can set it as follows, ^_^!

# Vi/etc/xinetd. d/telnet Service telnet { Disable = No # activate the telnet service, no Bind = 210.45.160.17 # Your IP Only_from = 210.45.0.0/16 # Only 210.45.0.0 ~ is allowed ~ 210.45.255.255 Only_from = .edu.cn # Only CERNET can access! No_access = 210.45.160. {115,116} # these two IP addresses cannot be logged on Access_times =--# The service is only available for these two periods of time every day. ...... }

Vi. login from telnet Root User

For the sake of security, the linxu system does not allow the root account to directly access the system from the remote telnet. If you want to use the root identity management system, you should first enter the system with a common user account, and then run the "Su-" command to convert it to a root user.

Direct telnet to Linux. In the case of blue point 1.0, the function of limiting root users to direct telnet to the system is handled by pam.

In the/etc/PAM. d/login file, you can find:

Auth required/lib/security/pam_securetty.so

This pam_securetty.so file will read the securetty file in the/etc/directory. If the user logs on to the TTY file at the/etc/securetty location, allow the connected user to log on to the host using the root account. So we only need to add a "#" at the beginning of this line to shield this line.