How to Kill a Process in Linux: Terminate Processes Using the Kill and Killall Commands

When managing a Linux server, you may encounter unresponsive or malfunctioning processes that consume system resources, slow down your work, and negatively impact other running processes. Knowing how to kill a process in Linux is essential for efficient system administration.

This article will guide you through various methods to terminate unresponsive processes in Linux. Whether you are a beginner or an experienced administrator, these methods will help you manage processes effectively in a Linux environment.

What is the kill Process in Linux?

The kill command in Linux terminates a running, unresponsive, or malfunctioning process in a controlled and safe manner.

How to Locate a Process in Linux

Before terminating a process, it’s crucial to identify it correctly. Fortunately, Linux provides several tools for this. The ps and top commands are among the most common.

The ps command shows a snapshot of all running processes, allowing you to find the Process ID (PID) of a specific process. Basic usage:

ps [options]

Common options include:

• -a: shows processes for all users.

• -u: shows processes for the current user.

• -x: includes processes without a terminal.

To narrow the list, combine it with grep. For example, to list all running Java processes:

ps -aux | grep java

The top command provides a dynamic view of all running processes and their resource usage. It requires no additional arguments for basic use.

For more focused searches, pidof and pgrep are useful.

pidof finds a process’s PID by its name:

pidof [options] [process_name]

Example: pidof nginx returns the PID of NGINX processes. Options include:

• -c: returns only PIDs in the current root directory.

• -o: omits specified PIDs.

• -s: returns only one PID, typically the oldest.

pgrep provides flexible searches by name or other properties:

pgrep [options] [pattern]

Example: pgrep -u username finds processes run by a specific user. Options include:

• -n: returns the newest matching process.

• -o: returns the oldest matching process.

• -u: matches processes owned by the specified user.

  
  

Kill Command Signals

After identifying the process, send the appropriate signal using kill. Each signal serves a different purpose and affects how the process ends.

List all available signals:

kill -l

Common signals:

• SIGTERM (15): default and safest signal for orderly termination.

• SIGKILL (9): immediately stops a process without cleanup.

• SIGSTOP (19): pauses a process without terminating it.

• SIGHUP (1): indicates terminal disconnection, often ending the process.

• SIGINT (2): interrupts a process, typically via Ctrl+C.

Specify the signal by name or number. Use SIGTERM for safe shutdowns, SIGKILL only when necessary.

How to Kill a Process in Linux

After understanding signals, here are methods to kill processes on a Linux server. If using a VPS, connect via SSH (e.g., with PuTTY).

Using Holy VPS Browser Terminal:

1. Log in to Panel → VPS section.

2. Select your server and access SSH credentials.

3. Click Browser Terminal to open a terminal in a new tab.

4. Log in with SSH credentials.

5. Use kill to terminate a process, e.g.:

kill 63772

Where 63772 is the PID.

Killing a Process Using kill with a PID

To kill a single process:

kill 12345

This sends SIGTERM to PID 12345.

For a forced kill:

kill -9 12345

Killing Multiple Processes

Kill multiple PIDs at once:

kill 12345 67890 13579

Or use a pattern with pgrep:

kill $(pgrep pattern)

Killing a Process Using pkill

pkill kills processes by name or other attributes:

pkill apache

Options:

• -u username: kill processes owned by a user.

• -t terminal: kill processes attached to a terminal.

• -l: list processes with PIDs.

Be careful—pkill apache kills all matching names.

Killing a Process Using killall

killall requires the exact process name:

killall apache

Options include:

• -o [time]: kill processes older than specified time.

• -y [time]: kill processes newer than specified time.

Example: Kill Chrome processes running over 30 minutes:

killall -o 30m chrome

Conclusion

We hope this guide has been helpful! 🚀 Remember, don’t hesitate to ask questions on the HolyHosting Discord or contact our support team.

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