CentOS开启telnet服务

CentOS5.8上安装telnet服务

1.查看系统版本及是否安装telnet

[root@centos32 comodo]# cat /etc/issue
CentOS release 5.8 (Final)
Kernel \r on an \m
[root@centos32 comodo]# rpm -qa|grep telnet
telnet-0.17-39.el5

其中CentOS系统默认已经安装了telnet，但是telnet-server软件包需要自行安装

2.安装telnet-server

1.可以下载rpm包安装（下载地址:）

2.可以#yum install telnet-server

安装完成后检查安装是否成功：

[root@centos32 comodo]# rpm -qa|grep telnet
telnet-0.17-39.el5
telnet-server-0.17-39.el5

3.启动telnet服务

方法1：图形桌面System->Administration->Services->"On Demand Services"菜单页选中telnet并保存

方法2：图形桌面Applications->Accessories->Terminal中输入#/usr/sbin/ntsysv回车选中telnet并保存

方法3：修改/etc/xinetd.d/telnet将disable = yes修改为no, 可以使用命令#sed -i 's/disable = yes/disable = no/' /etc/xinetd.d/telnet

方法4：修改启动项#/sbin/chkconfig telnet on

方法3和方法4需要重启telnet服务,运行命令#/etc/rc.d/init.d/xinetd restart

4.测试服务

[root@centos32 comodo]# telnet localhost
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
CentOS release 5.8 (Final)
Kernel 2.6.18-308.16.1.el5 on an i686
login: comodo
Password:
Last login: Thu Dec  6 15:19:27 from debian32
[comodo@centos32 ~]$ exit(此处可知telnet已经使用用户comodo成功登录)
logout

Connection closed by foreign host.
[root@centos32 comodo]#

5.允许root登录telnet（默认情况下，telnet禁止root用户登录）

方法1.修改/etc/pam.d/remote注释掉auth required pam_securetty.so

[root@centos32 comodo]# vim /etc/pam.d/remote
#%PAM-1.0
#auth       required     pam_securetty.so

方法2.先查看root登录使用的伪终端号，然后把这个伪终端加到/etc/securetty中

step 1:打开一个终端输入

[root@centos32 comodo]# telnet localhost
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
CentOS release 5.8 (Final)
Kernel 2.6.18-308.16.1.el5 on an i686
login: root
Password:
Login incorrect

login: Login timed out after 60 seconds
Connection closed by foreign host.

step 2:打开一个终端输入

[root@centos32 comodo]#tail /var/log/secure
Dec  6 15:51:15 centos32 login: pam_securetty(remote:auth): access denied: tty 'pts/7' is not secure !
Dec  6 15:51:18 centos32 login: FAILED LOGIN 1 FROM centos32 FOR root, Authentication failure

step 3:把pts/7加入到/etc/securetty后，telnet即可使用root账户登录

[root@centos32 comodo]# vim /etc/securetty
pts/7