失敗原因：
1.telnet套件未安裝，檢查telnet套件是否已安裝：
[root@vm-rhel root]# rpm -qa telnet telnet-0.17-25
表示已安裝
2.telnet套件已安裝，telnet-server未安裝，檢查telnet-server套件是否安裝：
[root@vm-rhel root]# rpm -qa telnet-server telnet-server-0.17-25
表示已安裝
3.telnet#設定檔問題：
[root@vm-rhel root]# cat /etc/xinetd.d/telnet
# default: on
# description: The telnet server serves telnet sessions; it uses \
# unencrypted username/password pairs for authentication.
service telnet
{
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID
disable = yes
}將disable對應的值修改為no或註解該行並重啟xinetd守護程式：service xinetd restart。
[root@vm-rhel root]# service iptables status Table: filter Chain INPUT (policy ACCEPT) target prot opt source destination RH-Lokkit-0-50-INPUT all -- anywhere anywhere Chain FORWARD (policy ACCEPT) target prot opt source destination RH-Lokkit-0-50-INPUT all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain RH-Lokkit-0-50-INPUT (2 references) target prot opt source destination ACCEPT udp -- 192.168.1.1 anywhere udp spt:domain dpts:1025:65535 ACCEPT tcp -- anywhere anywhere tcp dpt:smtp flags:SYN,RST,ACK/SYN ACCEPT tcp -- anywhere anywhere tcp dpt:http flags:SYN,RST,ACK/SYN ACCEPT tcp -- anywhere anywhere tcp dpt:ftp flags:SYN,RST,ACK/SYN ACCEPT tcp -- anywhere anywhere tcp dpt:ssh flags:SYN,RST,ACK/SYN ACCEPT tcp -- anywhere anywhere tcp dpt:telnet flags:SYN,RST,ACK/SYN ACCEPT udp -- anywhere anywhere udp spts:bootps:bootpc dpts:bootps:bootpc ACCEPT udp -- anywhere anywhere udp spts:bootps:bootpc dpts:bootps:bootpc ACCEPT all -- anywhere anywhere ACCEPT all -- anywhere anywhere REJECT tcp -- anywhere anywhere tcp dpts:0:1023 flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable REJECT tcp -- anywhere anywhere tcp dpt:nfs flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable REJECT udp -- anywhere anywhere udp dpts:0:1023 reject-with icmp-port-unreachable REJECT udp -- anywhere anywhere udp dpt:nfs reject-with icmp-port-unreachable REJECT tcp -- anywhere anywhere tcp dpts:x11:6009 flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable REJECT tcp -- anywhere anywhere tcp dpt:xfs flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
表示未關閉,如果防火牆已關閉，則不需要在/etc /sysconfig/iptables設定檔中新增：-A RH-Lokkit-0-50-INPUT -p tcp -m tcp --dport 23 --syn -j ACCEPT。
關閉防火牆：service iptables stop (重新啟動後失效：防火牆開機自動啟動)
啟動防火牆：service iptables start
#重啟防火牆： service iptables restart
禁止防火牆開機自動啟動：chkconfig iptables off
5.預設情況下Linux不允許root使用者以telnet方式登入Linux主機，若要允許root使用者登入可採用以下3方法：
（1）修改/etc/pam.d/login設定檔
RedHat Linux對於遠端登入的限制體現在/etc/pam.d/login檔中，把限制內容註解即可。
[root@vm-rhel root]# cat /etc/pam.d/login#%PAM-1.0auth required pam_securetty.so auth required pam_stack.so service=system-auth #auth required pam_nologin.so account required pam_stack.so service=system-auth password required pam_stack.so service=system-auth session required pam_stack.so service=system-auth session optional pam_console.so
（2）移除/etc/securetty資料夾
驗證規則設定在/etc/securetty檔案中，定義了root使用者只能在tty1-tty6的終端機上記錄，刪除該檔案或將其改名即可避開驗證規則從而實現root使用者以telnet方式遠端登入Linux主機。
[root@vm-rhel root]# mv /etc/securetty /etc/securetty.bak
（3）先用一般使用者登錄，再切換到root使用者
[bboss@vm-rhel bboss]$ su root Password: [root@vm-rhel bboss]#
#
以上是關於telnet到RedHat Linux失敗的解決方法詳解的詳細內容。更多資訊請關注PHP中文網其他相關文章！
