How to Stop a Running Command in Ubuntu

  • Post category:Ubuntu

At times, you may need to stop a running command in Ubuntu, whether it’s stuck, consuming too many resources, or simply no longer required. In this guide, we’ll cover several methods to stop both foreground and background processes.

Stopping a Foreground Command

When a command is running in the terminal and you want to stop it, here are the methods you can use:

1. Using Ctrl+C

The most common way to stop a command in the terminal is by pressing Ctrl+C. This sends a SIGINT (Signal Interrupt) to the process, terminating it immediately.

Example:

If you’re running a command like ping, pressing Ctrl+C will stop it and return you to the prompt.

2. Using Ctrl+Z

If you don’t want to terminate a command but only suspend it temporarily, press Ctrl+Z. This sends a SIGTSTP (Signal Stop) signal to the process and pauses it, allowing you to continue later.

Example:

If you’re working with a text editor like gedit, pressing Ctrl+Z will stop the application but keep it in memory.

You can resume the suspended process by typing:

fg

This will bring the process back to the foreground.

Stopping a Background Command

For commands running in the background or processes started by the system, you have a few additional options.

1. Using the kill Command

The kill command is a universal method to terminate processes. To stop a process, you first need its Process ID (PID). You can find the PID by running:

ps aux | grep [process_name]

Once you have the PID, use the following command to stop the process:

kill [PID]

If the process doesn’t stop, you can use a more forceful signal, SIGKILL (signal 9):

kill -9 [PID]

2. Using pkill Command

The pkill command allows you to kill processes by name, eliminating the need to find their PID manually:

pkill [process_name]

Example:

To kill all instances of Firefox, run:

pkill firefox

3. Using killall Command

Similar to pkill, killall terminates all processes that match a specific name:

killall [process_name]

Example:

To kill all instances of gedit, use:

killall gedit

4. Using xkill for GUI Applications

If you’re dealing with a graphical application, xkill is a handy utility. After running xkill, your mouse cursor will change to a cross or skull icon. Simply click on the window you want to close.

To install xkill, use:

sudo apt install x11-utils

5. Using top or htop

Both top and htop are tools for monitoring processes. You can also use them to kill processes by PID.

Using top:

  • Run top in your terminal.
  • Press k, then enter the PID of the process you want to kill.
  • Optionally, specify a signal (default is 15, SIGTERM).

Using htop:

  • Open htop by running htop in the terminal.
  • Navigate to the process with the arrow keys, press F9, and choose the signal you want to send.

Conclusion

Stopping a running command or process in Ubuntu can be easily achieved using various tools like Ctrl+C, kill, pkill, and others. Always be careful when using the kill -9 option, as it can forcefully terminate processes, potentially leading to data loss.

By understanding these methods, you can efficiently manage and control processes on your Ubuntu system.