kill Cheatsheet
Basic Syntax
Core kill command forms.
| Command | Description |
|---|---|
kill PID |
Send SIGTERM (graceful stop) to a process |
kill -9 PID |
Force kill a process (SIGKILL) |
kill -1 PID |
Reload process config (SIGHUP) |
kill -l |
List all available signal names and numbers |
kill -0 PID |
Check if a PID exists without sending a signal |
Signal Reference
Signals most commonly used with kill, killall, and pkill.
| Signal | Number | Description |
|---|---|---|
SIGHUP |
1 |
Reload config — most daemons reload settings without restarting |
SIGINT |
2 |
Interrupt process — equivalent to pressing Ctrl+C |
SIGQUIT |
3 |
Quit and write a core dump for debugging |
SIGKILL |
9 |
Force kill — cannot be caught or ignored; always terminates immediately |
SIGTERM |
15 |
Graceful stop — default signal; process can clean up before exiting |
SIGUSR1 |
10 |
User-defined signal 1 — meaning depends on the application |
SIGUSR2 |
12 |
User-defined signal 2 — meaning depends on the application |
SIGCONT |
18 |
Resume a process that was suspended with SIGSTOP |
SIGSTOP |
19 |
Suspend process — cannot be caught or ignored |
SIGTSTP |
20 |
Terminal stop — equivalent to pressing Ctrl+Z |
Kill by PID
Send signals to one or more specific processes.
| Command | Description |
|---|---|
kill 1234 |
Gracefully stop PID 1234 |
kill -9 1234 5678 |
Force kill multiple PIDs at once |
kill -HUP 1234 |
Reload config for PID 1234 |
kill -STOP 1234 |
Suspend PID 1234 |
kill -CONT 1234 |
Resume suspended PID 1234 |
kill -9 $(pidof firefox) |
Force kill all PIDs for a process by name |
killall: Kill by Name
Send signals to all processes matching an exact name.
| Command | Description |
|---|---|
killall process_name |
Send SIGTERM to all matching processes |
killall -9 process_name |
Force kill all matching processes |
killall -HUP nginx |
Reload all nginx processes |
killall -u username process_name |
Kill matching processes owned by a user |
killall -v process_name |
Kill and report which processes were signaled |
killall -r "pattern" |
Match process names with a regex pattern |
Background Jobs
Kill jobs running in the current shell session.
| Command | Description |
|---|---|
jobs |
List background jobs and their job numbers |
kill %1 |
Send SIGTERM to background job number 1 |
kill -9 %1 |
Force kill background job number 1 |
kill %+ |
Kill the most recently started background job |
kill %% |
Kill the current (most recent) background job |
Troubleshooting
Quick fixes for common kill issues.
| Issue | Check |
|---|---|
Process does not stop after SIGTERM |
Wait a moment, then escalate to kill -9 PID |
No such process error |
PID has already exited; verify with ps -p PID |
Operation not permitted |
Process belongs to another user — use sudo kill PID |
SIGKILL has no effect |
Process is in uninterruptible sleep (D state in ps); only a reboot can free it |
| Not sure which PID to kill | Find it first with pidof name, pgrep name, or ps aux | grep name |
Related Guides
| Guide | Description |
|---|---|
| kill Command in Linux | Full guide to kill options, signals, and examples |
| How to Kill a Process in Linux | Practical walkthrough for finding and stopping processes |
| pkill Command in Linux | Kill processes by name and pattern |
| pgrep Command in Linux | Find process PIDs before signaling |
| ps Command in Linux | Inspect the running process list |
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