How to terminate the process?

To terminate a process in Linux, you can use the commands kill, pkill, or killall.

1. Using kill:

• Terminates a process by its Process ID (PID).
• Requires knowing the PID of the process.
• Signals:
  • SIGTERM (default, 15): Graceful termination, allows the process to exit properly.
  • SIGKILL (9): Immediate and forceful termination, cannot be ignored by the process.

# find the PID of the process
ps aux | grep <process_name>

# send SIGTERM signal (default)
kill <PID>

# send SIGKILL signal
kill -9 <PID>

2. Using pkill:

• Terminates processes by name or other attributes.
• Does not require knowing the PID.
• Supports pattern matching.

# terminate all processes named 'nginx'
pkill nginx

# terminate all processes containing 'myapp' in their name (case-insensitive)
pkill -i myapp

# send SIGKILL to processes named 'firefox'
pkill -9 firefox

3. Using killall:

• Terminates processes only by their exact name.
• Does not support complex pattern matching like pkill.

# terminate all processes named 'apache2'
killall apache2

# send SIGKILL to processes named 'mysqld'
killall -9 mysqld

Choice of command:

Command	Method of termination	Requires PID	Pattern support
kill	By PID	Yes	No
pkill	By name/attributes	No	Yes
killall	By exact name	No	No

In most cases, it is recommended to first try terminating the process with SIGTERM (kill <PID>, pkill <name>) to allow it to save data and exit properly. SIGKILL (kill -9, pkill -9, killall -9) should be used only as a last resort when the process does not respond to other signals.