Enable telnet for CentOS

1. view the linux version: [loong @ localhost ~] $ Cat/etc/issueCentOSrelease5.8 (Final) Kernel \ ronan \ m2. check whether telnet-server is installed in the system. telnet-client (or telnet) is installed in the linux system by default ), telnet-server must be manually installed. [Loong @ localhost

1. view the linux version information:

[loong@localhost ~]$ cat /etc/issueCentOS release 5.8 (Final)Kernel \r on an \m

2. check whether telnet-server is installed in the system. telnet-client (or telnet) is installed in linux by default, while telnet-server must be installed manually.

[loong@localhost ~]$ rpm -qa | grep telnettelnet-0.17-39.el5

3. install telnet-server. skip this step if the system is already installed.

Method 1: Download RPM resource telnet-server,: http://rpmfind.net/linux/rpm2html/search.php? Query = telnet-server

Select the corresponding version of telnet-server to download;

Installation: # rpm-I telnet-server-0.17-39.el5.i386.rpm # seems to have to install xinetd separately.

Method 2: (recommended)

# Yum install telnet-server

After installation:

[loong@localhost ~]$ rpm -qa | grep telnettelnet-0.17-39.el5telnet-server-0.17-39.el5

4. start the telnet service.

Method 1: System-> Administration-> Services,

Select telnet in On Demand Services,

Select xinetd in Background Services, and click Start above, which is displayed on the right: xinetd (pid 15986) is running...

Save & Quit.

Method 2: edit/etc/xinetd. d/telnet and change disable = yes to no.

After modification:

# default: on# description: The telnet server serves telnet sessions; it uses \#       unencrypted username/password pairs for authentication.service telnet{        disable = no        flags           = REUSE        socket_type     = stream        wait            = no        user            = root        server          = /usr/sbin/in.telnetd        log_on_failure  += USERID}

Method 3: Use the chkconfig command to directly enable

[root@localhost loong]# chkconfig telnet on

Note: Method 2 and method 3 require the xinetd service to be activated. The method is as follows:

[root@localhost loong]# service xinetd restartStopping xinetd:                                           [  OK  ]Starting xinetd:                                           [  OK  ]

Or:

[root@localhost loong]# /etc/rc.d/init.d/xinetd restartStopping xinetd:                                           [  OK  ]Starting xinetd:                                           [  OK  ]

5. test services

[root@localhost loong]# telnet localhostTrying 127.0.0.1...Connected to localhost.localdomain (127.0.0.1).Escape character is '^]'.CentOS release 5.8 (Final)Kernel 2.6.18-308.1.1.el5 on an i686login: loongPassword: Last login: Tue Apr 24 16:42:06 from 10.108.14.135[loong@localhost ~]$ exitlogoutConnection closed by foreign host.[root@localhost loong]# 

telnet> o localhostTrying 127.0.0.1...Connected to localhost.localdomain (127.0.0.1).Escape character is '^]'.CentOS release 5.8 (Final)Kernel 2.6.18-308.1.1.el5 on an i686login: rootPassword: Login incorrectlogin:     Login incorrectlogin: Login incorrectlogin: Connection closed by foreign host.[root@localhost loong]# tail -20 /var/log/secureApr 24 17:32:58 localhost login: pam_securetty(remote:auth): access denied: tty 'pts/1' is not secure !Apr 24 17:33:03 localhost login: FAILED LOGIN 1 FROM localhost FOR root, Authentication failure

You can see access denied: tty 'PTS/1' is not secure!

Therefore, add 'PTS/1' to/etc/securetty to enable logon as the root user of telnet. Why? It is unclear.

Method 2: modify/etc/pam. d/remote and comment out auth required pam_securetty.so.

1 #%PAM-1.02#auth       required     pam_securetty.so3 auth       include      system-auth

Note: it is not recommended to enable telnet root logon, which may cause security risks.