How to Kill a Running Linux Process

The kill command in Linux is used to terminate processes by sending specific signals. By default, it sends the SIGTERM signal (signal 15), which gracefully stops a process. However, other signals, like SIGKILL (9), can forcefully terminate a process when necessary.

Terminate a Process by PID

kill 1234  

Sends the default SIGTERM signal to gracefully terminate process 1234.

Forcefully Kill a Process

kill -9 1234  

• -9 sends the SIGKILL signal, which forcefully terminates the process.

Reload a Process (e.g., Web Server)

kill -1 1234  

• -1 sends the SIGHUP signal, often used to reload configurations (e.g., Nginx, Apache).

Stop a Process Temporarily

kill -19 1234  

• -19 sends the SIGSTOP signal, pausing the process.

Resume a Stopped Process

kill -18 1234  

• -18 sends the SIGCONT signal, resuming a paused process.

List All Available Signals

kill -l  

Displays a list of all signals (e.g., SIGTERM, SIGKILL, SIGHUP).

More Read

How to Remove Empty Directories in Linux

How to Search Text or String in Files on Linux

How to Copy Files and Directories in Linux cp Command Examples

How to Move or Rename Files and Directories in Linux

Kill a Process by Name

pkill firefox  

Terminates all processes named firefox.

Kill Processes by User

pkill -u username  

Terminates all processes owned by username.

Kill Processes Matching a Pattern

pkill -f "python script.py"  

• -f: Matches the full command line (e.g., kills python script.py).

Send a Custom Signal

kill -SIGUSR1 1234  

Sends the SIGUSR1 signal, often used for custom process handling.

Kill All Processes in a Process Group

kill -- -12345  

• -- -12345: Sends the signal to all processes in the process group 12345.

Kill Background Jobs

kill %1  

Terminates the background job with ID 1 (use jobs to list background jobs).

Gracefully Stop Multiple Processes

kill 1234 5678 91011  

Sends SIGTERM to processes 1234, 5678, and 91011.

Verify if a Process Was Killed

kill -0 1234  

• -0 checks if the process exists without sending a signal.
• Returns 0 if the process exists, 1 if it doesn’t.

Kill All Processes Except the Current Shell

kill -9 -1  

• -1: Sends SIGKILL to all processes except the current shell.
• Warning: Use with caution—this can crash the system.

Key Notes:

• Signals: Use kill -l to list all signals. Common ones include:
• SIGTERM (15): Graceful termination.
• SIGKILL (9): Forceful termination.
• SIGHUP (1): Reload configurations.
• Permissions: Only the root user or process owner can kill processes.
• Alternatives: Use pkill or killall to target processes by name.