Configure and use telnet in redhatlinux9

Article Title: Configure and use telnet in redhatlinux9. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
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
　　
Telnet is not safe. By default, the root user is not allowed to use telnet to access the Linux host. To allow the root user to log on, use the following methods:
[Root @ wljs/root] # vi/etc/pam. d/login
# Auth required pam_securetty.so # Add comments to this line!
　　
Or
[Root @ wljs root] # mv/etc/securetty. bak
In this way, the root user can directly access the Linux host. However, we recommend that you do not do this. You can also switch to the root user after a common user enters, with the root permission.