Logged into the console today and found the following output

There are 20 zombie processes

Upon checking, it turned out not to be what I imagined. Its definition (reprinted from Jianshu) is as follows:

APEU2's definition of a zombie process: In UNIX System terminology, a process that has terminated, but whose parent has not yet waited for it, is called a zombie. When a parent process does not call the wait method to obtain the termination status of the child process when the child process ends, the child process becomes a zombie process after termination.

Hazards of zombie processes

When a child process ends, it sends a SIGCHLD signal to the parent process. The parent process enters the wait method to release related resources, close open files, etc. When the parent process does not know the child process has ended and does not enter the wait method to release related resources, a large number of zombie processes will occupy a large amount of system resources; on the other hand, the process ID of the child process is still occupied, and when a large number of zombie processes appear, it will cause the system to be unable to create new processes.

Definitely not a good thing.

So we can enter the following command to view all zombie processes:

ps aux | grep Z

We use the following commands to solve it

ps -eo pid,ppid,stat,cmd | grep 'Z'  # Find zombie processes and their parent processes

kill -HUP <PPID>  # Send SIGHUP signal to the parent process, where <PPID> is the parent process ID

Alternatively, you can choose to terminate the parent process