How to Find the PID and PPID Linux [7 Easy Methods]

TL;DR

To easily find PID and PPID Linux, follow these steps:

  1. Open your Terminal application.
  2. List all processes with ps aux command in Linux.
  3. Find the PID and PPID for a specific process with ps aux | grep [process-name] (the second column shows the PID, the third column shows the PPID).

Ever struggled with managing processes on your Linux system? Knowing the PID (Process ID) and PPID (Parent Process ID) of running processes can make your life much easier. In this post, I’ll show you how to find these IDs using simple, effective methods. Whether you’re a system administrator or a developer, these techniques will help you monitor and manage your processes more efficiently. Expect to learn about commands like ps, pgrep, top, pidof, and pstree that will streamline your process management tasks. Let’s get started!

What Are PID and PPID of a Process in Linux?

In Linux, every process is assigned a unique identifier called a Process ID (PID), which is used by the system to manage process execution and resources. Here’s what PID and PPID mean:

  • PID (Process ID): This is the unique number assigned to a process when it starts. This ID is used by the system to refer to the process during its lifetime, for tasks like scheduling, resource allocation, and process management.
  • PPID (Parent Process ID): This is the PID of the process that started (or spawned) the current process. Essentially, the PPID points to the process’s parent. Understanding the relationship between processes and their parents can help in managing processes and understanding system behavior.

These IDs are crucial for system management tasks such as monitoring system activities, sending signals to processes (like to terminate a process), and managing process priorities. They are typically viewed using commands like ps, top, or htop, where you can see both the PID and PPID for all running processes.

How to Find the PID and PPID Linux?

To find the PID and PPID Linux, you can use several methods. First, the ps aux | grep [process-name] command lists all processes, showing the PID in the second column and the PPID in the third. The pgrep [process-name] command directly outputs the PID. Use top, then press f, navigate to PPID, and enable it for real-time process monitoring.

The /proc/[PID]/status file also contains PID and PPID information. With htop, you can view PIDs and PPIDs interactively. The pidof [process-name] command quickly finds the PID of a running program. Finally, pstree -p visualizes the process tree with PIDs, providing a clear hierarchical view.

That’s the quick summary. Now, here are the detailed instructions for each method to find the PID and PPID of a process in Linux:

1. ps Command

The ps command is used to display information about active processes on a Linux system. It’s a powerful tool for monitoring the processes running and managing system resources. Follow these steps to find the PID using the ps command:

  1. Start by opening your Terminal application.
open terminal
  1. Type the following command to list all processes:
ps aux

This command lists all active processes along with detailed information.

listing all active processes
  1. To find the PID and PPID for a specific process, use the grep command:
ps aux | grep [process-name]

In the output, the second column will display the PID, and the third column will display the Linux PPID of the filtered processes.

viewing PID using ps command

2. pgrep Command

pgrep simplifies the task of locating processes by name or other attributes and directly outputs their PIDs, making it quicker to find process IDs without parsing full process lists. Here is the step-by-step process:

  1. Access your Terminal window.
  2. Enter the command below to find the PID of a process by its name:
pgrep [process-name]

Replace the process-name with the process name of which you find the PID.

viewing PID using pgrep command
  1. To find the PPID, use the PID obtained and check it with the ps command:
ps -f -p [PID]

The output will show PPID along with other details of the process.

viewing PPID by using PID

3. top Command

top is typically used for real-time monitoring of system resources and processes. It’s interactive and updates process information periodically, making it ideal for ongoing system management. Here is the step-by-step guide to find the PID and PPID in Linux:

  1. Start by launching your Terminal.
  2. Simply type the following command to see a list of processes:
top

This command displays a dynamic list of processes.

viewing dynamic list of processes
  1. Press f to select which columns to display. 
go to column configuration
  1. Navigate to PPID and press space to enable it. Press Enter to save the configuration.
enabling PPID column
  1. With PPID now enabled, you can easily read both PID and PPID from the top display.
enabled PPID in top menu

4. /proc Directory

The /proc directory contains a virtual filesystem with detailed information about the system and processes. It is useful for accessing real-time systems and process information directly from the filesystem. Follow these steps to find the PPID and PID in Linux:

  1. Open your Terminal interface.
  2. Enter the directory of a specific PID to examine its details:
cd /proc/[PID]

Replace PID with the PID of the directory to which you want to navigate.

entering the directory of PID
  1. Check the status of the file by running the command:
cat status | grep 'Pid\|PPid'

This command checks the status file to find PPID and other details.

finding PPID from the directory

5. htop Command

htop offers an enhanced, interactive overview of system processes, which can be easier to navigate and more visually informative than top. It allows for real-time process management. Here is how to do it:

  1. If not already installed, you can install htop using:
sudo apt install htop

The command will install htop on your Ubuntu system.

installing htop on ubuntu
  1. To launch htop, simply type htop in the Terminal.
launching htop on ubuntu
  1. Press F2 to enter setup.
go to setup menu

6. Using pidof Command

The pidof command in Linux helps you quickly find the Process ID (PID) of a running program. This is particularly useful for monitoring, debugging, or terminating processes efficiently.

  1. Launch your terminal application.
  2. To find the PID of a specific process, type:
pidof firefox

This command finds and displays the PID of the Firefox process.

viewing pid of a specific process

7. Using pstree Command

The pstree command visualizes the hierarchical structure of running processes, showing parent-child relationships. It’s useful for understanding process hierarchies and managing processes effectively.

  1. Access your command window.
  2. To view the entire process tree, type:
pstree

This command displays all running processes in a tree format.

viewing entire process tree
  1. To display PIDs in the process tree, use:
pstree -p

This command shows each process with its corresponding PID.

viewing pid in process tree
  1. To view the process tree for a specific user, use:
pstree -u [username]

This command displays the process tree for processes owned by the user guestuser.

viewing process tree of a specific user

Best Practices for Secure Process Management in Linux

Managing processes securely in Linux is crucial for maintaining system integrity and preventing unauthorized access or data breaches. These practices help administrators enforce security policies effectively and safeguard their environments. Here are five key practices:

  • 🔒 Use Least Privilege Principle: Always run processes with the minimum permissions necessary to perform their tasks. Avoid using root privileges unless absolutely necessary, as this can prevent potential system-wide security risks.
  • 🔏 Regularly Update Software: Keep all system software and applications updated. Security patches often include fixes for vulnerabilities that could be exploited by malicious processes. Use package managers like apt, yum, or dnf for consistent updates.
  • 🔐 Monitor and Audit Processes: Implement continuous monitoring with tools like auditd or syslog to log and analyze process activities. Regular auditing helps in detecting unusual process behaviors that could indicate a security threat.
  • 🛡️ Use Process Sandboxing: Sandbox environments can isolate processes, limiting their access to system resources and reducing the risk of process-level attacks. Tools like Firejail or SELinux can enforce strict boundaries around processes.
  • 🚨 Implement Access Controls: Define strict access control policies using SELinux or AppArmor to manage which resources a process can access. Tailoring access controls helps minimize potential damage if a process is compromised.

Final Thoughts

In this article, I have explored step-by-step methods to find the PID and PPID of a process in Linux using commands like ps, pgrep, top, pidof, and pstree. These techniques are crucial for efficient system management, helping you monitor, debug, and manage processes securely and effectively.

For more learning, check out these related articles:

Frequently Asked Questions

  1. What is the ps Command?

    The ps command in Unix-based systems is a utility for displaying information about active processes. It allows users to view the current running processes on their system, including details like the process ID (PID), terminal associated with the process, the user running the process, CPU usage, and the command line that initiated the process. This command is vital for system monitoring, management, and troubleshooting tasks.

  2. What is pgrep Command?

    The pgrep command is a utility in Unix-like operating systems that searches for processes currently running on the system based on criteria specified by the user. It returns the process IDs (PIDs) that match the given conditions, making it useful for scripting and process management. This command can be particularly helpful for finding processes by name, user, group, or other attributes without needing to parse the full output of the ps command.

  3. What is top Command?

    The top command is a task manager program in Unix-based systems that provides a dynamic, real-time view of the system’s running processes. It displays a detailed summary of process activity, including information such as CPU and memory usage, process ID, user information, and prioritization. This tool is essential for system administrators and users to monitor system performance and manage tasks effectively.

  4. What is /proc Directory?

    The /proc directory is a virtual filesystem in Unix-like operating systems that provides a window into the kernel’s internal state, allowing users and programs to query or control system resources and settings. It does not contain real files but runtime system information, such as system memory, devices mounted, hardware configuration, and active processes (each process is represented by a directory with its process ID as the name). This makes /proc invaluable for system monitoring and troubleshooting tools.

  5. What is htop Command?

    The htop command is an interactive process viewer for Unix systems that serves as an enhanced version of the traditional top command. It provides a colorful and user-friendly interface for monitoring system processes in real time. htop allows users to manage processes easily, including sorting them by various criteria, searching for specific processes, and performing actions like killing or renicing processes directly from its interface. This tool is particularly appreciated for its usability improvements over top.

  6. How can I change the priority of a process using its PID?

    You can change the priority of a process using its PID with the renice command. This command adjusts the “niceness” of a process, which affects its priority in the CPU scheduling. Lowering the niceness value gives the process a higher priority, ensuring it receives more CPU time, which can be crucial when managing resource allocation for critical tasks.

  7. What are the differences between ps and pgrep when it comes to performance?

    Using ps combined with grep can be less efficient than pgrep, especially on systems with many active processes. The ps command generates a complete list of all processes, which grep then filters, whereas pgrep directly searches for processes matching the criteria, reducing processing time and resource usage.

  8. Can I find the entire process tree for a specific PID?

    Yes, you can visualize the entire process tree for a specific PID using the pstree command. This command displays the tree structure of all processes, making it easier to understand the hierarchy and relationships between a parent process and its child processes, which is particularly useful for comprehensive system analysis and debugging.

Ojash

Author

Ojash is a skilled Linux expert and tech writer with over a decade of experience. He has extensive knowledge of Linux's file system, command-line interface, and software installations. Ojash is also an expert in shell scripting and automation, with experience in Bash, Python, and Perl. He has published numerous articles on Linux in various online publications, making him a valuable resource for both seasoned Linux users and beginners. Ojash is also an active member of the Linux community and participates in Linux forums.

Akshat

Reviewer

Akshat is a software engineer, product designer and the co-founder of Scrutify. He's an experienced Linux professional and the senior editor of this blog. He is also an open-source contributor to many projects on Github and has written several technical guides on Linux. Apart from that, he’s also actively sharing his ideas and tutorials on Medium and Attirer. As the editor of this blog, Akshat brings his wealth of knowledge and experience to provide readers with valuable insights and advice on a wide range of Linux-related topics.

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