How to change the LINUX daemon and disable the port

========================================== Daemon knowledge ============================================
In linux, there are many daemon processes, and most servers use daemon. At the same time, the daemon completes many system tasks, such as job planning process crond and printing process lqd.

A Brief Introduction to common daemon processes:
Kudzu (hardware detection) sshd (remote connection) inetd (network connection) ldap (Directory Access Protocol)

Linux running level:
The most commonly used is 3, 5.

Run level 0: it is used for shutdown. When it is started, it will be used for shutdown.
Run level 1: In Single user mode, only the root account is allowed to log on, mainly for system maintenance.
Run level 2: enables all users to log on, but does not enable NFS working, that is, there is no network function
Run level 3: enables all users to log on and have complete functions. It contains functions not available in run level 2, but is in text mode after startup.
Run level 4: defined by the user, but it is identical to run level 3 by default,
Run level 5: similar to run level 3, the only difference is that the graphic interface is used after the startup,
Run level 6: restart. Restart immediately after startup

Chkconfig changes the running level of the daemon:
You can use the MAN Chkconfig command to view help information.
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Use the Netstat command:
Netstat-tn view current open port
Netstat-tnl: port used to view the listener status

Use Lsof with netstat to check which program is started on the corresponding port:
Lsof-I: 111 view the PID value and COMMAND of the program port 111
Kill 9441 close the port with PID 9441

Ntsysv graphical tool to disable unwanted services