How to Identify and Kill a Running Process in Linux

In Linux, managing processes is a key part of system administration. You can identify and terminate (or “kill”) processes using several commands. Here’s a guide on how to identify and kill a running process on a Linux server.

1. Identify a Process by Name or ID #

The first step is to identify the process you want to stop. This can be done using commands like ps, top, htop, and pgrep.

Using ps Command #

The ps command shows a snapshot of current processes.

• List all processes:
  • Note the PID of the process that you want to kill

ps aux

• Find a specific process by name:
  • Replace process_name with the name of the process you’re searching for.
  • Take note of the PID

ps aux | grep process_name

Using top Command #

top provides a real-time view of running processes and can help you identify high-resource-consuming processes.

• Start top:
  • Note the PID of the process you want to kill.
  • Press q to quit top.

top

Using htop (if installed) #

htop is an interactive tool that provides an easy-to-use interface for managing processes.

• Start htop:

htop

• Navigate to the process and press F9 to kill it.

2. Kill a Process by PID #

Once you’ve identified the PID of the process, you can use the kill command to terminate it.

• Basic kill command:
  • Replace PID with the actual process ID.

kill PID

• Common Kill Signals

The kill command uses different signals to terminate a process:

• SIGTERM (signal 15): Politely asks a process to stop.
  • If you input a PID that does not exist, you will see an output that says there is no such process.

kill -15 PID

SIGKILL (signal 9): Forces a process to stop immediately, without cleanup.

kill -9 PID

3. Kill All Instances of a Process by Name #

To kill all instances of a particular process by name, use the pkill or killall commands.

Using pkill #

pkill can terminate processes based on their name.

• Kill processes by name:

pkill process_name

Using killall #

killall kills all instances of a process by name. This is useful for stopping multiple instances.

• Kill all instances of a process:

killall process_name

4. Check if the Process was Successfully Terminated #

Use either of the commands below to check if the process is still running.

ps aux | grep process_name or pgrep process_name

Summary of Commands #

• Identify Process:
  • ps aux
  • pgrep process_name
  • top or htop
• Kill Process by PID:
  • kill PID
  • kill -9 PID (force kill)
• Kill All by Name:
  • pkill process_name
  • killall process_name

These commands provide an efficient way to identify and kill processes on Linux, essential for effective system management and troubleshooting.