Linux telnet service enabled (1)

Today, a company employee got a Red Hat Enterprise 5 installation. After the system was installed, it was found that telnet was not available, and ssh was acceptable. It took a long time to get it done. Combined with the previous information on this aspect, refer to the following:

1. Summary linux provides services by running daemon in the background.

The work of the daemon is to open a port) and wait for the listen to enter the connection. In C/S mode, if the customer requests a connection, the daemon creates a fork sub-process to respond to the connection, and the parent process continues to listen to requests from other services.

However, if every service provided by the system must run a daemon listening for a port connection, it usually means a waste of system resources. To this end, the "extended network daemon" xinetdxinetd internet daemon is introduced ). The telnet service is also protected by xinetd.

2. Checks whether the rpm packages of telnet and telnet-server are installed.

OS: RedHat9

[Root @ localhost root] # rpm-qa telnet

Telnet-0.17-25 // telnet *. rpm is installed by default //

[Root @ localhost root] # rpm-qa telnet-server

Null

// Telnet *. rpm is not installed by default //

3. Install the telnet-server 3rd disk with the telnet-server-0.17-25.i386.rpm [root @ localhost root] # rpm-ivh telnet-server *. i386.rpm -- this package depends on the xinet package.

4. Modify the telnet service configuration file vi/etc/xinetd. d/telnet

Service telnet

{

Disable = yes

Flags = REUSE

Socket_type = stream

Wait = no

User = root

Server =/usr/sbin/in. telnetd

Log_on_failure + = USERID

}

Add "#" to the front of the disable = yes line, or change it to "disable = no ".

PS:

After telnet-server is installed, files/usr/sbin/in. telnetd are available.

5. Restart the xinetd daemon. Because the telnet service is also protected by xinetd, after the telnet-server is installed, you must restart the xinetd to start the telnet service.

[Root @ localhost root] # service xinetd restart

Or

[Root @ localhost root] #/etc/init. d/xinetd restart

6. Disable the system firewall. If it cannot be modified, first modify the user Authentication method and then try (setup-> Authentication configuration). The default firewall in linux is "high"

CLI:

[Root @ localhost root] # setup

Select: "firewall configuration"

Select security level -- "no firewall"