How to Kill a Process in Linux: kill, pkill, kill -9

Sometimes a program hangs, eats all the CPU, or holds a port you need. Stopping it takes two steps: find its process ID (PID), then send it a signal.

Step 1: find the process

ps aux | grep node

deploy   4821  2.1  3.4 1203456 140320 ?  Sl  09:12  0:42 node server.js

The second column, 4821, is the PID. (Ignore the line for grep node itself.)

Shorter:

pgrep -a node        # list matching PIDs with their command lines

Or interactively with top or htop — sort by CPU or memory to find the culprit. (Basic Linux commands)

Step 2: stop it

Politely first

kill 4821

kill sends SIGTERM by default: "please shut down". Well-behaved programs finish what they're doing, close connections, and exit. (Graceful shutdown in Node.js)

Check it's gone:

ps -p 4821

Forcefully if it won't

kill -9 4821

-9 is SIGKILL: the kernel stops the process immediately. It can't refuse, but it also can't clean up — open files may be left half-written, temporary files left behind, in-flight requests dropped. Use it after SIGTERM has had a few seconds.

By name instead of PID

pkill -f "node server.js"   # match against the full command line
killall node                # every process named node — careful

killall node stops every Node process, including ones you didn't mean. Prefer pkill -f with a specific pattern.

Kill whatever is using a port

The classic "port 3000 is already in use" fix. Find the process:

sudo lsof -i :3000
# or
sudo ss -tlnp | grep :3000

Then kill its PID. A one-liner:

sudo kill $(sudo lsof -t -i :3000)

Or with fuser:

sudo fuser -k 3000/tcp

(Ports explained, Docker port already allocated)

"I killed it and it came straight back"

That's a process manager doing its job — systemd, PM2, Docker's restart policy or Supervisor restarts the app when it dies. Stop it through the manager instead:

sudo systemctl stop myapp
pm2 stop myapp
docker stop myapp

(What is systemd?, PM2 vs systemd)

Permission denied

You can only kill your own processes. To stop another user's (or root's), use sudo kill. Think twice before killing system processes you don't recognise.

On macOS and Windows

macOS: the same ps, kill, pkill, lsof commands work, or use Activity Monitor.
Windows: tasklist and taskkill /PID 4821 /F, or Task Manager. For ports: netstat -ano | findstr :3000.

Signals cheat sheet

Signal	Number	Meaning
SIGTERM	15	Please stop (default for `kill`)
SIGINT	2	Interrupt — what Ctrl+C sends
SIGHUP	1	Hang up — many servers reload config on it
SIGKILL	9	Stop now, no clean-up

Before you reach for kill -9

If an app keeps hanging or using too much memory, killing it treats the symptom. Check the logs for why. (Finding memory leaks in Node.js, How container CPU and memory limits work)

EasySpawn runs your apps under a process manager that restarts them if they crash, and Claude Code can find and stop a runaway process for you from a plain-English request. See how it works or join the waitlist.

How to Kill a Process in Linux (kill, pkill, killall, and Ports)