AnQiCMS 作为一个基于 English 语言开发的 high-performance enterprise-level content management system，其 core lies in providing stable, efficient content management services.For any server-side application that requires long-term operation, such as AnQiCMS, it is crucial to ensure that it can run stably after startup, even if the terminal session that starts it is closed.nohupCommand assistant to start AnQiCMS process, and the survival of the process after the terminal is closed, which is closely related to the process management mechanism of the Linux system and the process identifier (PID).

Linux process and terminal session association

In the Linux system, when we start a program through the SSH client or local terminal, the program is typically run as the foreground process of the terminal session.This means it is closely connected to the terminal, and is part of the terminal session.Each terminal session has a session leader (session leader), as well as one or more process groups (process group), and the processes started belong to a process group of the current terminal session.

This connection is characterized by the fact that when the terminal session ends (for example, closing the SSH window or exiting the terminal emulator), the operating system sends a specific signal to all processes in that session, that is,SIGHUP(Hang Up)。This signal's default behavior is to terminate the process that receives it.SIGHUPSignal, and terminate the operation immediately.

Without usingnohupStart AnQiCMS: consequences.

To be specific, if there is no,nohupCommand to directly start the AnQiCMS process under the package and close the current terminal window after startup, then the AnQiCMS process will stop running.This is unacceptable for backend applications like AnQiCMS that require continuous online services, as the website will become inaccessible immediately.

The design goal of AnQiCMS is to provide 24/7 online content management services for small and medium-sized enterprises and content operation teams, which means it needs to run continuously in the background like a daemon.The ordinary terminal startup method cannot meet this requirement because once the terminal is closed, the processes associated with the terminal session will receive a termination signal.

nohupfunction

nohup命令（No Hang Up 的缩写）正是为了解决上述问题而设计的。它的主要功能是让进程忽略SIGHUP信号。当一个进程通过nohupAt startup, it will be set to not receive signals at the end of a terminal session, allowing it to continue running in the background after the terminal closes.SIGHUPIgnoring signals, other than

信号，SIGHUP信号，nohupIt will also redirect the standard input (stdin), standard output (stdout), and standard error (stderr) of the process. Typically, it will redirect the standard output and standard error to a file namednohup.outThe file (if the file does not exist, it will be created), standard input comes from/dev/null.The benefits of doing this are that the process will not be affected even if the terminal that starts it is closed, thus completely disconnecting from the terminal and not affected by the lack of output or input.start.shis explicitly used in the scriptnohupIt is for this reason, to ensure that AnQiCMS can continue to run.

The role of the Process ID (PID)

The process identifier (PID) is a unique number assigned by the operating system to each running process.It is like the ID number of a process, used for internal identification and management of processes.nohupStill withoutnohupIt will also get a PID.

However, the PID itself does not determine the lifecycle of the process. Whether a process survives or not depends more on its association with the terminal session and its response to system signals (such asSIGHUPThe response mechanism of “）。nohupThe command's purpose is to change the processSIGHUPThe response to the signal (ignoring it), rather than changing how the process retrieves PID.

When an AnQiCMS process terminates due to terminal closure, its PID will be**recycled by the system, becoming available, and may be allocated to a new process in the future.Therefore, PID is simply an identifier that reflects that a process is running at a certain point in time, but it cannot predict the behavior or life cycle of the process under specific conditions.

Ensure continuous operation of AnQiCMS recommended practices

Given that AnQiCMS needs to run continuously online, simply running the program directly in the terminal is not enough to support the production environment. In addition to usingnohupIn addition to this simple and direct method, more robust and professional production environment deployments usually adopt process guard tools.

For example, you can configure it on a Linux system,systemdService to manage AnQiCMS process. Throughsystemd，AnQiCMS can be configured to start automatically when the system boots, and to restart automatically in the event of a failure, while ensuring it runs in the background as a daemon, detaching from any user session. Similar tools includeSupervisorThese tools provide more comprehensive process management, logging, and error recovery mechanisms, which are the**practice**to ensure the long-term stability of AnQiCMS.

Summary

Withoutnohupwhen launched AnQiCMS process and then close the terminal, the process will terminate because it receivedSIGHUPthe signal.nohupis to make the process ignoreSIGHUPSignal, and redirect its standard I/O, so that it can continue to run in the background even after the terminal is closed.The process identifier (PID) is a unique identifier for a process. It does not directly determine the survival of the process, but the association with terminal sessions and the mechanism for responding to signals determine the lifecycle of the process.nohup或更专业的进程守护工具来确保其持续、稳定地运行。

Frequently Asked Questions (FAQs)

Q1: AnQiCMS 进程启动后，如何确认它是否在后台持续运行？

A1: You can go throughpsCommand to check if the AnQiCMS process is still running. In Linux or macOS terminals, you can try to runps -ef | grep anqicmsIf you see any process entries related to AnQiCMS (especially if you arestart.shThe executable file is renamed in the script, please use the corresponding name), it indicates that it is running. In addition, checknohup.outlog files (if usednohupStart), check if there are any new log outputs, which can also reflect the active status of the process.

Q2: If you accidentally close the terminal, will the AnQiCMS process really stop?

A2: Yes, if the AnQiCMS process is running withoutnohupor other process守护工具（如systemd）的情况下直接在终端中启动的，那么当您关闭该终端时，AnQiCMS 进程会收到SIGHUPSignal and terminate the run by default. Your website will therefore be inaccessible. This is why AnQiCMS officially providesstart.shThe script will use by defaultnohupThe reason for the command to avoid such unexpected termination.

Q3: BesidesnohupWhat methods can ensure that AnQiCMS runs continuously and achieves boot-up automatically?

A3: For production environments, it is recommended to use more professional process monitoring tools. On Linux systems,systemdis the mainstream choice, you can create asystemdThe service unit file is used to define the start, stop, and restart behaviors of the AnQiCMS process, and configure it to run automatically at system startup. In addition,Supervisoris also a popular process management tool, it can monitor process status and automatically restart processes when they crash, ensuring the continuity of services. These tools provide more thannohupMore powerful management and monitoring features.