Linux server-configure telnet
Configure telnet
Through the configuration file, we can set the connection time, number of connections, connection ip and so on of telnet to achieve a more secure connection.
1. Set the connection time. The parameter "access_times"
[root@localhost wj] # gedit / etc/xinetd.d/telnet
Service telnet
{
Flags = REUSE
Socket_type = stream
Wait = no
User = root
Server = / usr/sbin/in.telnetd
Log_on_failure + = USERID
Disable = no
Access_times = 08:00-09:00 13:00-15:00 / / the allowed connection period is 8: 9 o'clock, 13: 15 o'clock
}
[root@localhost wj] # service xinetd restart / / restart the service
Stop xinetd: [OK]
Starting xinetd: [OK]
[root@localhost wj] # telnet 192.168.0.119 / / attempt to connect
Trying 192.168.0.119...
Connected to 192.168.0.119.
Escape character is'^]'.
Connection closed by foreign host. / / connection failed
2. Set the number of connections. You can set the number of connections allowed by the parameter "instances". After that, you can no longer connect.
[root@localhost wj] # gedit / etc/xinetd.d/telnet
Service telnet
{
Flags = REUSE
Socket_type = stream
Wait = no
User = root
Server = / usr/sbin/in.telnetd
Log_on_failure + = USERID
Disable = no
Instances = 1 / / only one connection is allowed here, and the second cannot be connected.
}
[root@localhost wj] # service xinetd restart / / restart the service
Stop xinetd: [OK]
Starting xinetd: [OK]
[root@localhost wj] # telnet 192.168.0.119 / / first connection
Connected to 192.168.0.119.
Login: david
Password:
Last login: Thu Aug 16 09:10:22 from 192.168.0.119
Already login / / successful
[root@localhost wj] # telnet 192.168.0.119 / / second connection
Connected to 192.168.0.119.
Connection closed by foreign host. / / failed
3. Allow / disable login to a specific ip or network segment. Parameter "only-from"no_access"
[root@localhost wj] # gedit / etc/xinetd.d/telnet
Service telnet
{
Flags = REUSE
Socket_type = stream
Wait = no
User = root
Server = / usr/sbin/in.telnetd
Log_on_failure + = USERID
Disable = no
Only_from = 192.168.0.113 / / only 113 connections are allowed
# only_from = 192.168.0.0amp 24 / / allow 1mm 254 connection
# only_from = 192.168.0.100-192.168.0.200 / / 100 connections allowed
# only_from = 192.168.0. / / allow 113 and 114 connections
# no_access = 192.168.0.113 / / 113connection is prohibited, other words are the same as above
}
4. Allow root connection. As long as the file "/ etc/securetty" is deleted, the system cannot read the file and will naturally log in to root forever.
[root@localhost wj] # mv / etc/securetty / etc/securetty.bak / / rename the file
[root@localhost wj] # service xinetd restart / / restart the service
Stop xinetd: [OK]
Starting xinetd: [OK]
[root@localhost wj] # telnet 192.168.0.119 / / connection
Trying 192.168.0.119...
Connected to 192.168.0.119.
Login: root / / use root user connection
Password:
Last login: Thu Aug 16 07:51:45 from 192.168.0.119
Already login / / connected successfully
I have made a platform for Linux learning. At present, it comes out one by one, which you can refer to and use.
Link: https: / / pan.baidu.com/s/1GOLVU2CbpBNGtunztVpaCQ password: n7bk
