Process and Service Management - Handling Zombie Processes Incident

Introduction:

Zombie processes are a common issue in system administration. These are processes that have completed their execution but still have an entry in the process table. Handling incidents involving zombie processes is crucial for maintaining a healthy and responsive system. In this blog post, we will explore how to address zombie processes using a C program and relevant Linux commands.

Step 1: Understanding Zombie Processes

Zombie processes are created when a child process completes its execution, but the parent process fails to collect the exit status. These processes remain in the process table as "Z" (defunct) until the parent process collects the exit status using the wait() system call. A system with too many zombie processes can lead to resource depletion.

Step 2: Creating the Zombie Process

Let's create a simple C program (zombie.c) to generate a zombie process:

#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
    // fork() creates a child process identical to the parent
    int pid = fork();

    // if pid is greater than 0, it is the parent process
    // if pid is 0, it is the child process
    // if pid is -1, fork() failed to create a child process
    // Parent process
    if (pid > 0)
        sleep(600);
    // Child process
    else
        exit(0);

    return 0;
}

Compile the C program using the GCC compiler:

sudo apt install gcc
gcc zombie.c -o zombie

Run the compiled program:

./zombie

Step 3: Check for Zombie Processes

On a separate terminal or using the ps command, check for zombie processes:

ps -aux | grep -i defunct

Step 4: Addressing Zombie Processes

To address zombie processes, the parent process should collect the exit status of the child processes using the wait() system call. This ensures that the zombie processes are removed from the process table. Properly managing child processes in a real-world scenario will prevent the accumulation of zombie processes.

Conclusion:

Handling zombie processes is essential for maintaining a healthy system. By understanding the concept of zombie processes and using Linux commands like ps to identify them, administrators can effectively address incidents involving zombie processes. Properly managing child processes and collecting their exit status will prevent the accumulation of zombie processes and contribute to the overall stability of the system.

Regularly monitor process status and implement proper process management practices to avoid zombie process incidents.