root@2[/]# ifconfig

eth0 Link encap:Ethernet HWaddr 00:10:A4:9F:2B:FF

inet addr:192.168.1.254 Bcast:192.168.1.255 Mask:255.255.255.0

inet6 addr: fe80::210:a4ff:fe9f:2bff/64 Scope:Link

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:106942 errors:0 dropped:0 overruns:0 frame:0

TX packets:103319 errors:0 dropped:0 overruns:0 carrier:0

collisions:9 txqueuelen:1000

RX bytes:110201058 (105.0 MiB) TX bytes:11096727 (10.5 MiB)

Interrupt:11 Base address:0x4800

lo Link encap:Local Loopback

inet addr:127.0.0.1 Mask:255.0.0.0

inet6 addr: ::1/128 Scope:Host

UP LOOPBACK RUNNING MTU:16436 Metric:1

RX packets:4410 errors:0 dropped:0 overruns:0 frame:0

TX packets:4410 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:0

RX bytes:1030232 (1006.0 KiB) TX bytes:1030232 (1006.0 KiB)

我们现在来连接一下

root@2[/]# telnet 192.168.1.254

Trying 192.168.1.254...

Connected to 192.168.1.254.

Escape character is '^]'.

lcnja.8800.org login: root

Login incorrect

lcnja.8800.org login: lcnja

Password:

Last login: Mon Sep 27 20:51:33 2004 from localhost.localdomain on pts/3

Linux debian 2.6.8-1-686 #1 Tue Sep 14 00:22:58 EDT 2004 i686 GNU/Linux

The programs included with the Debian GNU/Linux system are free software;

the exact distribution terms for each program are described in the

individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent

permitted by applicable law.

lcnja@lcnja:~$

从上面我们可以看到我们已经连接成功了，但是使用root连接的时候会失败，因为默认的安全设置是限制root用户使用telnet连接主机的

本来因为telnet是明文传输的，所以处于安全考虑才限制了root从telnet登陆，如果你需要使用，那么如下修改

root@2[/]# nano /etc/pam.d/login

#

# The PAM configuration file for the Shadow `login' service

#

# NOTE: If you use a session module (such as kerberos or NIS+)

# that retains persistent credentials (like key caches, etc), you

# need to enable the `CLOSE_SESSIONS' option in /etc/login.defs

# in order for login to stay around until after logout to call

# pam_close_session() and cleanup.

#

# Outputs an issue file prior to each login prompt (Replaces the

# ISSUE_FILE option from login.defs). Uncomment for use

# auth required pam_issue.so issue=/etc/issue

# Disallows root logins except on tty's listed in /etc/securetty

# (Replaces the `CONSOLE' setting from login.defs)

#把下面在行注释掉

# auth requisite pam_securetty.so

# Disallows other than root logins when /etc/nologin exists

# (Replaces the `NOLOGINS_FILE' option from login.defs)

auth requisite pam_nologin.so

# This module parses /etc/environment (the standard for setting