How to Check Running Processes in Linux Using ps, top, htop & atop

Managing a Linux server involves more than installing applications and keeping the system updated. To check running processes activity effectively, it’s important to understand how Linux manages every service, from a web server and database to scheduled jobs and background scripts. When a website becomes slow, CPU usage suddenly spikes, or memory starts disappearing, the first place to investigate is the list of running processes.

Linux offers several built-in and advanced tools for monitoring what’s happening inside your system. Some provide a quick snapshot of active processes, while others continuously update resource usage in real time or record historical performance data for deeper analysis.

If you’re new to Linux administration, choosing between commands like ps, top, htop, and atop can be confusing because they all display process information in different ways. Knowing when to use each one can save time during troubleshooting and help you identify performance bottlenecks much faster.

In this guide, you’ll learn what each tool does and how to use it effectively with practical examples.

TL;DR

• Linux processes are running instances of applications or system services.
• The ps command provides a snapshot of currently running processes.
• top displays live CPU, memory, and process activity directly in the terminal.
• htop offers an interactive, user-friendly interface with easier navigation and process management.
• atop records system activity over time, making it useful for diagnosing performance issues that occurred earlier.
• Each tool serves a different purpose, and many administrators use them together for a more complete view of system performance.

Why Process Monitoring Matters in Linux

Every application running on your Linux server consumes system resources such as CPU time, memory, storage, or network bandwidth. Unexpected events like a runaway script, an overloaded web application, or a failing service can quickly affect overall system performance.

Regularly monitoring running processes helps you:

• Identify applications consuming excessive CPU or memory.
• Detect unresponsive or stuck processes.
• Troubleshoot slow server performance.
• Verify that essential services are running correctly.
• Monitor applications after deployments or configuration changes.
• Discover unusual resource usage before it impacts users.

Whether you’re managing a personal VPS or multiple production servers, understanding your system’s active processes makes troubleshooting significantly easier.

Tip: Process monitoring isn’t only for fixing problems. It’s equally useful for validating that a server is operating as expected after updates, deployments, or maintenance.

What Is a Linux Process?

A process is simply a program that is currently running on your Linux system. Every time you execute a command, start a service, or launch an application, Linux creates one or more processes to perform the required tasks.

For example:

• Starting the Apache or Nginx web server creates server processes.
• Connecting to a server over SSH starts a user session process.
• Running a backup script creates a temporary process until the job finishes.
• Database servers like MySQL or PostgreSQL continuously run multiple background processes to handle queries and maintenance tasks.

Each process is assigned a unique Process ID (PID), which allows the operating system to manage it independently.

Understanding these basics makes it much easier to interpret the output of process monitoring tools later in this guide. All utilities display process information, they solve different problems. Choosing the right one depends on whether you need a quick snapshot, continuous monitoring, easier navigation, or historical performance records.

When Should You Use Each Tool?

There’s no single “best” command for every situation. Instead, each utility fits a specific workflow.

Choosing the appropriate tool not only speeds up troubleshooting but also gives you more relevant information without unnecessary complexity.

Checking Running Processes with the ps Command

If you only need to verify whether a process is running or want a quick overview of active processes, the ps command is usually the best place to start.

This makes it ideal for quick checks, scripting, and troubleshooting tasks where you need accurate process information without continuously monitoring the system.

What Is the ps Command?

The ps (Process Status) command is a built-in Linux utility that displays information about running processes. It displays:

• Process IDs (PIDs)
• Parent process IDs (PPIDs)
• Process owner
• CPU and memory usage
• Running time
• Terminal association
• Current process state
• The command used to start the process

Since ps only displays the current state of the system, running it again later may produce different results if processes have started or stopped.

Basic Syntax

ps [options]

ps [options]

You will see output as mentioned below:

Without any options:

ps

ps

Example Output

PID   TTY          TIME     CMD
2184  pts/0        00:00:00 bash
2671  pts/0        00:00:00 ps

PID   TTY          TIME     CMD
2184  pts/0        00:00:00 bash
2671  pts/0        00:00:00 ps

What This Means

By default, this output is limited to processes running in your current terminal session.

Viewing Every Running Process

For most server management tasks, you’ll need to view every running process on the system rather than only those associated with your current terminal session.

Use:

ps -e

ps -e

or

ps -A

ps -A

Both commands display every running process on the system. This is especially useful when:

• Verifying background services
• Checking application status
• Confirming daemon processes are active
• Looking for unexpected programs

Display More Process Details

The default output is intentionally brief. To include additional information such as the parent process, owner, and startup details, use:

ps -ef

ps -ef

Sample Output

UID        PID  PPID  C STIME TTY      TIME CMD
root         1     0  0 Jul16 ?        00:00:03 systemd
root       728     1  0 Jul16 ?        00:00:01 sshd
mysql     1458  

   
      1  1 Jul16 ?        00:00:12 mysqld

UID        PID  PPID  C STIME TTY      TIME CMD
root         1     0  0 Jul16 ?        00:00:03 systemd
root       728     1  0 Jul16 ?        00:00:01 sshd
mysql     1458  

   
      1  1 Jul16 ?        00:00:12 mysqld

This format is commonly used when troubleshooting production servers because it provides much more context than the default view.

Finding a Specific Process

Instead of scanning hundreds of running processes manually, you can search for a particular application.

For example, to locate Nginx processes:

ps -ef | grep nginx

ps -ef | grep nginx

Example output:

root      1024     1  0 09:30 ? 00:00:00 nginx: master process
www-data  1051  1024  0 09:30 ? 00:00:00 nginx: worker process

root      1024     1  0 09:30 ? 00:00:00 nginx: master process
www-data  1051  1024  0 09:30 ? 00:00:00 nginx: worker process

Similarly, you can search for:

ps -ef | grep apache2
ps -ef | grep apache2
ps -ef | grep mysql

ps -ef | grep apache2
ps -ef | grep apache2
ps -ef | grep mysql

or any other service running on your server.

Tip: If the only result you see is the grep command itself, the target process is likely not running.

Show Processes for a Particular User

When multiple users share the same Linux server,

filtering processes by username can make the output much easier to read.

ps -u username

ps -u username

Example:

ps -u ubuntu

ps -u ubuntu

This displays only the processes owned by the ubuntu user. Common use cases include:

• Shared hosting environments
• Multi-user development servers
• Investigating resource usage for a specific account

Display Information for a Specific Process ID

If you already know the Process ID (PID), you can retrieve information about that process directly.

ps -p 1842

ps -p 1842

To display additional columns:

ps -fp 1842

ps -fp 1842

This is particularly useful when documentation or log files reference a specific PID during troubleshooting.

Customize the Output

One of the strengths of the ps command is its flexibility. Instead of displaying every available column, you can choose exactly what information you need.

For example:

ps -eo pid,user,%cpu,%mem,cmd

ps -eo pid,user,%cpu,%mem,cmd

Possible output:

PID   USER     %CPU %MEM COMMAND
1024  root      0.0  0.3 nginx
1458  mysql     4.2  6.8 mysqld
2083  ubuntu    0.1  1.2 node server.js

PID   USER     %CPU %MEM COMMAND
1024  root      0.0  0.3 nginx
1458  mysql     4.2  6.8 mysqld
2083  ubuntu    0.1  1.2 node server.js

Sort by Memory Usage

ps -eo pid,user,%mem,cmd --sort=-%mem

ps -eo pid,user,%mem,cmd --sort=-%mem

These commands place the busiest processes at the top of the list, making it much faster to identify potential bottlenecks.

Practical Examples

Check if the SSH service is running

ps -ef | grep sshd

ps -ef | grep sshd

Find the PID of a Node.js application

ps -ef | grep node

ps -ef | grep node

List only process IDs

ps -eo pid

ps -eo pid

Show CPU and memory usage together

ps -eo pid,user,%cpu,%mem,cmd

ps -eo pid,user,%cpu,%mem,cmd

Identify the highest CPU-consuming process

ps -eo pid,%cpu,cmd --sort=-%cpu | head

ps -eo pid,%cpu,cmd --sort=-%cpu | head

Adding head limits the output to the top entries, making the results easier to review.

Common Mistakes Beginners Make

Learning to use ps is straightforward, but a few common mistakes can lead to confusion.

When Should You Choose ps?

The ps command is an excellent choice when you need quick, accurate information without launching an interactive monitoring session.

Use it when you want to:

• Confirm that an application or service is running.
• Retrieve a process ID before sending a signal.
• Generate process reports in shell scripts.
• Inspect running services during troubleshooting.
• Create custom process lists for automation.

If you need to watch processes continuously as CPU and memory usage change in real time, however, ps is no longer the ideal tool.

In the next section, we’ll explore top, which provides a live, continuously updating view of your system and is often the first utility administrators use when diagnosing performance issues.

If you need to stop a misbehaving process after identifying it, check out our detailed guide on How to Kill a Running Process in Linux.

Monitoring Linux Processes in Real Time with top

The ps command shows the current state of running processes, but its output is static and doesn’t refresh automatically. When you need to monitor CPU usage, memory consumption, or system load as they change, the top command is the better choice.

What Is the top Command?

The top command is a built-in Linux monitoring tool that displays a live, continuously updating view of system performance and active processes, making it ideal for troubleshooting performance issues in real time.

It’s particularly useful for:

• Diagnosing slow server performance
• Identifying CPU-intensive applications
• Finding memory-hungry processes
• Monitoring services after deployments
• Troubleshooting unexpected load spikes

Because the display refreshes automatically, you can observe how processes behave over time instead of relying on a single snapshot.

Launching top

Open your terminal and run:

top

top

Within a few seconds, your terminal transforms into a live monitoring interface.

Understanding the top Interface

Although the screen may appear busy at first, it’s organized into two primary sections.

System Summary

The top portion provides an overview of your server’s health, including:

• Current system uptime
• Number of logged-in users
• Load averages
• CPU utilization
• Physical memory usage
• Swap memory usage
• Total running and sleeping processes

This information gives you an immediate sense of whether the system is under normal load or experiencing resource pressure.

Process List

The lower section displays active processes. Some of the most useful columns include:

These values update automatically, making it easy to spot changing resource usage.

Although running top without options is enough in most situations, several command-line options make it even more useful.

Monitor a Specific User

To display only the processes owned by a particular user:

top -u username

top -u username

Example:

top -u ubuntu

top -u ubuntu

This reduces clutter when multiple users share the same server.

Watch Specific Processes

If you already know a process ID, monitor only that process.

top -p 2458

top -p 2458

This is especially useful while testing an application or observing resource usage after restarting a service.

Display Full Command Lines

Instead of showing only executable names:

top -c

top -c

This displays the complete command used to launch each process, making it easier to distinguish between similar applications.

Run in Batch Mode

Sometimes you need to save monitoring output for later analysis:

top -b -n 5

top -b -n 5

This captures five updates before exiting.

You can also redirect the output into a file:

top -b -n 5 > process_report.txt

top -b -n 5 > process_report.txt

Batch mode is commonly used in automation scripts and scheduled diagnostics.

Useful Interactive Shortcuts

Once top is running, you can adjust many settings directly from the interface without restarting the command. Several keyboard shortcuts let you adjust the display instantly.

Learning just a few of these shortcuts can significantly improve your workflow.

When Is top the Right Choice?

The top command shines when you need to observe how a server behaves over time. Typical scenarios include:

• A website becomes slow during peak traffic.
• CPU usage suddenly reaches 100%.
• Memory consumption keeps increasing.
• You suspect a process has entered an infinite loop.
• You want to verify resource usage immediately after deployment.

Since the display refreshes continuously, you can watch changes as they happen instead of repeatedly rerunning commands.

Limitations of top

Although top is extremely useful, it isn’t perfect. Some common limitations include:

• The interface can feel overwhelming for beginners.
• Navigation relies entirely on keyboard shortcuts.
• Finding a specific process among hundreds can take time.
• Colors and layout vary between Linux distributions.
• Historical performance data isn’t retained.

For many administrators, these limitations lead them to an enhanced alternative: htop.

Why Many Linux Users Prefer htop

If you find top difficult to navigate, htop offers a more user-friendly alternative. It provides the same core process information in a cleaner, color-coded interface with features like search, filtering, tree view, and easier process management.

For many Linux administrators, htop is the preferred tool for everyday system monitoring.

Installing htop

Unlike ps and top, htop isn’t installed by default on many Linux distributions.

Ubuntu and Debian

sudo apt update
sudo apt install htop

sudo apt update
sudo apt install htop

RHEL, AlmaLinux, Rocky Linux, and CentOS

sudo dnf install htop

sudo dnf install htop

Older CentOS versions may use:

sudo yum install htop

sudo yum install htop

Launch htop

Once installed, start it by running:

htop

htop

You’ll immediately notice a cleaner interface compared to top.

What Makes htop Different?

Instead of presenting a wall of constantly changing text, htop organizes information in a more user-friendly way.

Some improvements include:

• Color-coded CPU, memory, and swap usage
• Vertical and horizontal scrolling
• Easy process searching
• Interactive filtering
• Tree view for parent-child processes
• Mouse support in supported terminals
• Function-key shortcuts displayed on screen

These features make htop easier to learn and use, especially for those new to Linux administration.

Useful Keyboard Shortcuts

Unlike top, many common actions are visible directly on the screen, making navigation much easier.

Common Use Cases for htop

htop is particularly helpful when you need to:

• Search for a specific application quickly
• Sort processes by memory or CPU usage
• Kill misbehaving processes interactively
• Understand parent-child process relationships
• Monitor multiple applications during deployments

Because of its intuitive interface, it’s often recommended for developers and system administrators who spend a lot of time managing Linux servers.

top vs htop

If top gives you the information you need, there’s no requirement to switch. However, if you frequently troubleshoot servers, htop can make the process considerably faster and more comfortable.

Looking Beyond Real-Time Monitoring with atop

Both top and htop are great for monitoring what’s happening right now, but they can’t show what happened before you logged in.

That’s where atop is different. It records system activity over time, allowing you to review historical CPU, memory, disk, and process usage. This makes it especially useful for investigating intermittent performance issues and identifying resource bottlenecks that are no longer active.

Using atop for Advanced Linux Process Monitoring

The atop command combines real-time monitoring with historical performance logging, giving you a more complete view of your system’s behavior. It’s particularly valuable on production servers, where occasional CPU spikes, memory pressure, or disk I/O issues may occur outside your monitoring window.

By reviewing past activity, atop helps you diagnose problems that live monitoring tools might miss.

Installing atop

Most Linux distributions don’t install atop by default, so you’ll need to add it manually.

Ubuntu and Debian

sudo apt update
sudo apt install atop

sudo apt update
sudo apt install atop

RHEL, AlmaLinux, Rocky Linux, and CentOS

sudo dnf install atop

sudo dnf install atop

Older CentOS releases may require:

sudo yum install atop

sudo yum install atop

After installation, some distributions automatically enable the logging service, while others may require you to start or enable it manually.

Starting atop

Launch the interactive interface with:

atop

atop

Like top, you’ll see continuously updating statistics, but atop provides additional information about system resources and supports reviewing previously recorded data.

What Information Does atop Display?

atop combines system-wide metrics with process-level statistics.

System Overview

You’ll typically find information about:

• CPU utilization
• Memory and swap usage
• Disk activity
• Network throughput
• System uptime
• Load averages

Process Details

Each running process can display information such as:

This combination makes atop one of the most comprehensive monitoring tools available from the command line.

Helpful Keyboard Shortcuts

While atop is running, these shortcuts make navigation easier.

Switching between these views allows you to focus on the resource that’s currently causing performance issues.

When Should You Use atop?

atop becomes especially valuable when you’re troubleshooting issues that don’t happen consistently.

Common examples include:

• A server becomes slow during overnight backup jobs.
• CPU usage spikes only during scheduled tasks.
• Memory usage gradually increases over several hours.
• Disk I/O occasionally becomes saturated.
• Performance complaints occur before administrators are available to investigate.

Because historical data is available, you can often identify the root cause without reproducing the problem.

Choosing the Right Linux Process Monitoring Tool

Each command covered in this guide has its own strengths. Rather than replacing one another, they’re often used together depending on the task.

A practical workflow might look like this:

1. Use ps to verify that a service is running.
2. Switch to top if you notice high resource usage.
3. Open htop for easier navigation and process management.
4. Review atop logs if the issue happened earlier and you need historical data.

Selecting the right monitoring tool for the task can help you identify and resolve Linux server issues more efficiently.

Best Practices for Monitoring Linux Processes

Regardless of which utility you use, following a few good habits can make troubleshooting more efficient.

Monitor Before Making Changes
Check current resource usage before restarting services or applying updates. Having a baseline makes it easier to determine whether a change improved or worsened performance.

Watch Trends Instead of Single Readings
A brief spike in CPU or memory usage isn’t always a problem. Look for sustained patterns before taking action.

Identify the Root Cause
Avoid terminating processes simply because they’re consuming resources. A busy process may be performing legitimate work, such as handling web traffic or database queries.

Combine Multiple Tools
No single command provides every answer. Using ps, top, htop, and atop together often gives a more complete understanding of what’s happening on your server.

Keep Monitoring Utilities Updated
Newer package versions may include bug fixes, improved compatibility, and additional features that enhance monitoring accuracy.

Common Process Monitoring Problems and Solutions

Conclusion

Understanding what’s happening inside a Linux system is an essential skill for anyone responsible for servers, applications, or development environments. Whether you’re confirming that a service is running, investigating high CPU usage, or analyzing performance trends over time, the right monitoring tool can help you reach answers much faster.

Instead of relying on a single utility, become comfortable switching between ps, top, htop, and atop based on the situation. Each command offers a different perspective, and together they provide a well-rounded toolkit for diagnosing performance issues and keeping Linux systems running smoothly.

As your infrastructure grows, consistent process monitoring becomes an important part of proactive server management rather than just a troubleshooting step.

FAQs

Key Takeaways

• Linux provides multiple tools for monitoring running processes, each designed for different scenarios.
• ps is ideal for quick process lookups and scripting.
• top provides a continuously updated view of system activity.
• htop simplifies process monitoring with an interactive interface and built-in management features.
• atop adds historical performance tracking, making it easier to diagnose intermittent issues.
• Choosing the right tool depends on whether you need a snapshot, live monitoring, or historical analysis.

Manage Your Linux Servers More Efficiently with ServerAvatar

Command-line tools are invaluable for inspecting processes and diagnosing performance issues, but day-to-day server administration often involves much more than monitoring resource usage.

Tasks like deploying applications, configuring web servers, managing PHP versions, securing websites with SSL, scheduling backups, and overseeing multiple servers can quickly become time-consuming.

If you’re looking for a simpler way to manage Linux servers without giving up flexibility, ServerAvatar provides a centralized dashboard for handling these routine administration tasks. It complements your command-line workflow, allowing you to spend less time on repetitive management and more time building and maintaining your applications.

About the Author

Meghna Meghwani is a technical writer focused on Linux, Ubuntu, VPS hosting, server management, WordPress, PHP, Node.js, cloud hosting, and DevOps. She creates beginner-friendly tutorials, practical hosting guides, troubleshooting articles, and server security content designed to help developers and businesses manage applications and servers more efficiently.