📘 ** Exit Status Code = 143 in Bash**

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🎯 What You Will Learn

1. Understand what exit status code = 143 means in Bash.
2. Learn how SIGTERM (signal 15) works — the graceful termination signal.
3. Differentiate 143 from similar codes: 130 (SIGINT) and 137 (SIGKILL).
4. Detect when processes are ended normally by system shutdown, Docker stop, or admin command.
5. Handle and trap SIGTERM safely inside scripts.
6. Apply best practices in WordPress VPS automation, ensuring clean exits during restarts, backups, or container stops.

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1. 5W + 1H Framework

Element	Description
What	Exit code 143 means the process was terminated gracefully via SIGTERM (signal 15).
Why	SIGTERM is sent to stop a process politely, giving it a chance to clean up before exiting.
Who	Used by systemd, Docker, Kubernetes, and admins when stopping services or automation scripts.
When	When a process receives SIGTERM (kill, docker stop, systemctl stop) instead of abrupt SIGKILL.
Where	Common in background jobs, cron, Docker containers, or managed WordPress VPS tasks.
How	Bash computes 128 + signal_number → 128 + 15 = 143.

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2. Prerequisites

Before starting, you should:

• Understand signals in Bash (SIGINT, SIGTERM, SIGKILL).
• Know how to use commands like kill, ps, and trap.
• Be familiar with background processes (&) and service management (systemctl, docker stop).
• Have access to a Linux VPS environment.

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3. Core Syntax and Examples

🧩 Definition

Exit code 143 = process terminated by SIGTERM (signal 15) → graceful shutdown signal.

Example 1 – Sending SIGTERM with kill

sleep 60 &
kill -15 $!
wait $!
echo $?

Expected Output:

143

Explanation: Process was found and asked to terminate (SIGTERM), not forced. Bash reports exit code 143 = 128 + 15.

Example 2 – Graceful Docker Stop

docker run --name test -d ubuntu sleep 300
docker stop test
docker inspect test --format='{{.State.ExitCode}}'

Expected Output:

143

Explanation: Docker sends SIGTERM to the container before SIGKILL (after timeout). Container exits gracefully → exit code 143. Use Case (WordPress VPS): Gracefully stopping a running PHP-FPM or Redis container.

Example 3 – systemd Service Stop

systemctl stop php8.3-fpm
echo $?

Expected Output (in logs):

php8.3-fpm[PID]: received SIGTERM, shutting down

Explanation: systemd uses SIGTERM to stop services like PHP-FPM or MySQL gracefully. The exit code is reported as 143. Use Case: When rebooting a VPS or restarting the stack with systemctl restart lsws.

Example 4 – Handling SIGTERM in Script

#!/bin/bash
trap "echo 'Graceful stop detected'; exit 143" SIGTERM
echo "Running backup..."
sleep 60
echo "Backup completed."

Run it:

bash safe_exit.sh &
kill -15 $!
wait $!
echo $?

Expected Output:

Running backup...
Graceful stop detected
143

Explanation: The script traps SIGTERM, performs cleanup, and exits with 143 intentionally. Use Case: Gracefully stop WordPress backup jobs or WP-CLI updates during system shutdown.

Example 5 – System Sending SIGTERM Before Reboot

sudo reboot

Expected in logs:

systemd[1]: Stopping php8.3-fpm.service...
php-fpm[PID]: received SIGTERM, exiting gracefully

Explanation: During reboot, systemd sends SIGTERM to running processes. They log exit 143 as part of controlled shutdown.

4. Common Scenarios Triggering Exit Code 143

Scenario	Example	Description
Manual stop	kill PID or kill -15 PID	User requests graceful stop
System service stop	systemctl stop mysql	systemd sends SIGTERM
Docker container stopped	docker stop	Docker sends SIGTERM before kill
VPS reboot	reboot or shutdown	OS sends SIGTERM to all
Cron cleanup	Script terminates itself cleanly	Uses exit 143
Monitoring agent shutdown	service telegraf stop	SIGTERM issued to daemon

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5. WordPress VPS Use Cases

Use Case	Example	Explanation
Graceful PHP-FPM stop	systemctl stop php8.3-fpm	Ends requests safely
WP container shutdown	docker stop wp-site	Graceful exit of web app
Cron job interrupted	Admin sends kill	Script exits 143
Redis cache stop	systemctl stop redis-server	SIGTERM sent for safe data flush
WP backup abort	kill -15 PID	Backup stops safely, not corrupted
LiteSpeed reload	systemctl reload lsws	Workers gracefully end connections

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6. Troubleshooting Matrix

Symptom	Likely Cause	Diagnostic Command	Fix
Exit 143 logged	Graceful termination (SIGTERM)	journalctl -xe	Expected normal behavior
Process ends mid-task	Admin stop or reboot	last -x	Re-run job after reboot
Docker container exits 143	Container stop issued	docker logs <container>	Normal; verify graceful shutdown logs
Script halts unexpectedly	Received SIGTERM	trap handling missing	Add cleanup trap
WP tasks stop on cron overlap	Duplicate execution	Add lockfile mechanism

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7. Best Practices

1. Handle SIGTERM gracefully:

trap "echo 'SIGTERM received, exiting cleanly...'; exit 143" SIGTERM

2. Use traps for cleanup:

• Delete temp files.
• Close connections.
• Log event before exit.

3. Avoid force-killing processes: Use kill or systemctl stop instead of kill -9.
4. For containers: Always let Docker send SIGTERM before SIGKILL (default 10s timeout). Extend timeout if needed:

docker stop -t 30 wp-site

5. Automate logging of exits:

echo "$(date): Process exited with code $?" >> /var/log/exit_status.log

6. Use lock files in scripts to prevent multiple overlapping runs.

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8. Quick Lab – Simulate Exit Code 143

Step 1: Create a test script

nano /root/exit143_test.sh

Step 2: Insert

#!/bin/bash
trap "echo 'SIGTERM received, cleaning up...'; exit 143" SIGTERM
echo "Starting task..."
sleep 60
echo "Finished task."

Step 3: Run in background

bash /root/exit143_test.sh &
pid=$!

Step 4: Send SIGTERM

kill -15 $pid
wait $pid
echo $?

Expected Output:

Starting task...
SIGTERM received, cleaning up...
143

Explanation: Script exited gracefully when SIGTERM was received — exit code 143 confirms safe shutdown.

9. Cheat Sheet

Exit Code	Meaning	Description
0	Success	Normal completion
1	General error	Non-specific failure
2	Misuse of shell builtins	Syntax or structure error
126	Command cannot execute	Permission or binary issue
127	Command not found	Missing binary or path
130	Terminated by SIGINT	Manual interrupt (Ctrl+C)
137	Killed by SIGKILL	Forceful kill or OOM
139	Segmentation fault	Memory access violation
143	Terminated by SIGTERM	Graceful termination

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10. Mini-Quiz

1. What signal number corresponds to exit code 143?
2. What’s the difference between SIGTERM and SIGKILL?
3. Which system command sends SIGTERM to stop services gracefully?
4. How can you handle SIGTERM in a Bash script?
5. Why is exit code 143 considered a “normal” stop rather than an error?

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