This provides a location for external processes to relaunch cf-serverd if the process dies unexpectedly.
如果进程意外终止，这可以提供一个位置供外部进程重新启动 cf-serverd。
If the parent process dies before its children, the orphaned children need to know who is their parent process.
如果父进程在子进程之前终止，孤立的子进程需要知道它们的父进程是谁。
If the child dies before the parent, a signal is sent to the parent, and then the child moves to a zombie state until the signal is acknowledged, or the parent process is killed.
如果子进程在父进程之前终止，则会向父进程发送一个信号，然后子进程转变为僵死状态，直到该信号得到确认，或父进程被终止。
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