Quick Answer

# Send a normal termination request (SIGTERM)
kill 1234

# Force-kill the process (SIGKILL)
kill -9 1234

# Kill by process name instead of PID
pkill node

What You’re Trying to Do

A process is frozen and not responding, or a background command needs to be stopped, or something is still holding onto a port and needs to be shut down. kill sends a signal to a process ID — despite the name, it’s not always about force-killing. The default behavior is to politely ask the process to exit.

Environment

  • OS: Linux (Ubuntu / CentOS / Debian, etc.)
  • Useful commands: kill -l, ps aux, pgrep

Solution

1. Find the PID of the Process

ps aux | grep node
user   1234  0.5  1.2  912345  45678 pts/0   Sl   10:00   0:03 node server.js

The number in the second column, 1234, is the process ID (PID).

2. Send SIGTERM (Graceful Shutdown)

kill 1234

When no signal is specified, kill sends SIGTERM (15) by default. This asks the process to clean up (close files, drop connections) before exiting.

3. Send SIGKILL (Force Kill)

If the process doesn’t respond to SIGTERM, force it to stop.

kill -9 1234
# or
kill -SIGKILL 1234

SIGKILL terminates the process immediately at the OS level — it can’t be caught, ignored, or handled by the process, so it gets no chance to clean up. Use it only as a last resort.

4. Kill by Process Name (pkill / killall)

Looking up a PID every time gets tedious. You can target processes by name instead.

# Kill any process whose name partially matches
pkill node

# Kill a process with an exact name match
killall node
# Force-kill also works the same way
pkill -9 node

5. Kill Only a Specific User’s Processes

pkill -u www-data

6. List Available Signals

kill -l
 1) SIGHUP       2) SIGINT       3) SIGQUIT      9) SIGKILL
15) SIGTERM     ...

Common Errors

kill: (1234): No such process

The PID you specified has already exited, or you got the PID wrong. Check again with ps aux or pgrep.

pgrep -a node

Operation not permitted

You’re trying to kill a process you don’t own (owned by root or another user). Check your permissions.

sudo kill -9 1234

A Zombie Process Survives kill -9

A zombie process (state Z) has already finished executing — it’s just waiting for its parent to call wait() and reap it. kill can’t remove it; you need to restart or terminate the parent process instead.

ps aux | grep 'Z'

Killing Whatever Process Is Holding a Port

# Find and kill the process using port 3000
lsof -i:3000
kill -9 $(lsof -t -i:3000)

FAQ

Q: Is it okay to always use kill -9? Better to avoid it when possible. SIGKILL gives the process no chance to clean up, which can lead to corrupted files or inconsistent data. Try plain kill (SIGTERM) first, and only reach for -9 if the process doesn’t respond.

Q: What’s the difference between kill and pkill? kill sends a signal to a specific PID. pkill searches for matching processes by name or other criteria and can signal multiple processes at once.

Q: Should I use killall or pkill? killall matches process names exactly, while pkill also supports regex-style pattern matching. pkill is more flexible if you need finer control over the match.

Q: Are there other commonly used signals besides SIGTERM and SIGKILL? SIGHUP (1) is often used to tell a process to reload its configuration, and SIGINT (2) is what Ctrl+C sends.

Q: What’s the Windows equivalent? taskkill /PID 1234 /F behaves similarly to kill -9.

Q: Do I need kill just to stop a background shell job? For jobs running in your current shell, you can check the job number with jobs and target it directly, e.g. kill %1.

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