Linux server security policy details (6)

Article Title: Linux server security policy details (6 ). Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

4.2 daemon

4.2.1 concept of Linux daemon

Linux servers need to run many system services during startup. They provide Linux system function interfaces to local and network users and are directly oriented to applications and users. The programs that provide these services are executed by the daemons running on the background. System services are long-lived services that are independent of control terminals and periodically execute certain tasks or wait for some events to be handled. System services are often started during system boot and terminated when the system is shut down. System Services complete many system tasks, such as job planning service crond and printing service lqd. In Client/Server mode, the Server listener (Listen) waits for the Client to connect to a specific port. After the connection is successful, the Server and the Client communicate through the port. A daemon opens a port and waits for the Listen connection. If the client sends a connection request, the daemon creates a (Fork) subserver to respond to the connection, and the master server continues to listen to other service requests.

　4.2.2 list of services and daemon provided by Linux

The following describes in detail the services provided by Linux and their daemon processes. It is in alphabetical order, as shown in Table 4-2.

The service of the inuxsystem depends on the process. Doc

Select the system services to run based on your needs.

4.2.3 running mode of the Linux daemon

　1. Run the stand-alone daemon independently.

The init script is responsible for managing the independent daemon. the scripts of all the independent daemon are in the/etc/rc. d/init. d/directory. System services are independent daemon processes, including syslogd and cron. The standalone daemon is called stand-alone. It is an access mode in the traditional unix c/S mode. The working principle of the stand-alone mode is 4-4.

In stand-alone mode, the network services include xinetd, route, and gated. In addition, the Web server Apache and the mail server Sendmail and the Domain Name Server Bind. In Linux, services started in stand-alone mode are started by the symbolic link in the running level under/etc/rc. d.

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