Telnet installation and telnet (correct password) cannot log in!

telnet Installation and telnet( The password is correct ) Unable to login ！

1.telnet download

First in yum Find out whether there are these two installation packages in the source

test login: Connection closed by foreign host.
[[email protected] xinetd.d]# yum list | grep telnet
telnet.x86_64                            1:0.17-66.el7                 @updates 
telnet-server.x86_64                     1:0.17-66.el7                 @updates 
[[email protected] xinetd.d]# 

As mentioned above, we found two installation packages

2. install telnet

[[email protected] xinetd.d]# yum -y install telnet

[[email protected] xinetd.d]# yum -y install telnet-server

3.telnet After the installation is successful, we start telnet

because telnet The download is stored in xinetd among , But we start xinetd It is found that there is no dependent package .

[[email protected] xinetd.d]# service xinetd start
Redirecting to /bin/systemctl start xinetd.service
Failed to start xinetd.service: Unit not found.
[[email protected] xinetd.d]# 

4. download xinetd, And restart xinetd

[[email protected] xinetd.d]# yum -y install xinetd

[[email protected] xinetd.d]# service xinetd start         // Successful launch 
Redirecting to /bin/systemctl start xinetd.service
[[email protected] xinetd.d]# 
[[email protected] xinetd.d]# ls /etc/xinetd.d/        // But we found no telnet, So we have to create it ourselves 
chargen-dgram   daytime-dgram   discard-dgram   echo-dgram   tcpmux-server  time-dgram
chargen-stream  daytime-stream  discard-stream  echo-stream  telnet         time-stream
[[email protected] xinetd.d]# 

5. establish telnet, And write the text content

Pay attention to is , The first line in this text disable Medium yes To be converted into no

[[email protected] xinetd.d]# cd /etc/xinetd.d/
[[email protected] xinetd.d]# vi telnet
[[email protected] xinetd.d]# cat  telnet
service telnet
{
        disable = no
        flags           = REUSE
        socket_type     = stream
        wait            = no
        user            = root
        server          = /usr/sbin/in.telnetd
        log_on_failure  += USERID
 
}
[[email protected] xinetd.d]# 

Check the port number

[[email protected] xinetd.d]# netstat -tnl grep 23   //telnet Default port 23, It has been found below telnet Port number 
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN     
tcp6       0      0 :::22                   :::*                    LISTEN     
tcp6       0      0 :::23                   :::*                    LISTEN     
tcp6       0      0 ::1:25                  :::*                    LISTEN     
[[email protected] xinetd.d]# 

Here it is telnet The configuration is complete .

6.telnet（ The password is correct ） Unable to login

Here we are telnet But if the user password is correct , Still can't log in , Then we can directly ssh Connect in to make configuration changes

[[email protected] ~]# cat /etc/pam.d/login       // Notice the second line here auth [... Comment out , Then save to exit 
#%PAM-1.0
#auth [user_unknown=ignore success=ok ignore=ignore default=bad] pam_securetty.so
auth       substack     system-auth
auth       include      postlogin
account    required     pam_nologin.so
account    include      system-auth
password   include      system-auth
# pam_selinux.so close should be the first session rule
session    required     pam_selinux.so close
session    required     pam_loginuid.so
session    optional     pam_console.so
# pam_selinux.so open should only be followed by sessions to be executed in the user context
session    required     pam_selinux.so open
session    required     pam_namespace.so
session    optional     pam_keyinit.so force revoke
session    include      system-auth
session    include      postlogin
-session   optional     pam_ck_connector.so
[[email protected] ~]# 

7. restart telnet

[[email protected] ~]# service xinetd restart
Redirecting to /bin/systemctl restart xinetd.service
[[email protected] ~]# 

8. add to pts/0 And restart

By default linux All think pts0 Is an insecure connection , So I will refuse , Then I can release pts0, Raffi doesn't introduce too much here , If you want to ask what you think , You can go to /var/log/securre The query inside is the rejected Huo ....

[[email protected] ~]# cat /etc/securetty      // Enter this file , Add on last line pts/0
console
vc/1
vc/2
 A little .....
pts/0
[[email protected] ~]# 

restart xinetd

[[email protected] ~]# service xinetd restart
Redirecting to /bin/systemctl restart xinetd.service
[[email protected] ~]# 

After restarting, you can connect again , Enter the user and password to enter ！！！

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