Docker Docker Troubleshooting Understanding Exit Codes 0 1 125 126 127 128n 137 143

1. Core Command / Concept

Understanding exit codes helps diagnose and troubleshoot issues with Docker containers. docker run -it --rm.

2. Step-by-Step

1. Check the Docker version: docker --version
2. Run a simple container with an exit code: docker run -it --rm alpine /bin/echo "Hello World"
3. Check the exit code: echo $?
4. ⚠️ Delete all stopped containers: docker container prune
5. Run a container with a non-zero exit code: docker run -it --rm alpine /bin/false
6. Check the exit code: echo $?
7. Run a container with a specific exit code: docker run -it --rm alpine /bin/sh -c "exit 125"
8. Check the exit code: echo $?

3. Real Commands with Examples

1. Purpose: Run a container with a specific exit code.
   Command: docker run -it --rm alpine /bin/sh -c "exit 125"
   Brief explanation of flags: -it runs the container in interactive mode, --rm removes the container when it exits.

2. Purpose: Run a container with a non-zero exit code.
   Command: docker run -it --rm alpine /bin/false
   Brief explanation of flags: Same as above.

3. Purpose: Run a container with a zero exit code.
   Command: docker run -it --rm alpine /bin/echo "Hello World"
   Brief explanation of flags: Same as above.

4. Common Errors

1. Error message or symptom: docker: Error response from daemon: Container command 'exit 125' exited with code 125.
   Why it happens: The container exits with the specified code.
   One-line fix: docker run -it --rm alpine /bin/sh -c "exit 0"

2. Error message or symptom: docker: Error response from daemon: Container command '/bin/false' exited with code 1.
   Why it happens: The container exits with a non-zero code.
   One-line fix: docker run -it --rm alpine /bin/echo "Hello World"

3. Error message or symptom: docker: Error response from daemon: Container command '/bin/sh -c exit 125' exited with code 125.
   Why it happens: The container exits with the specified code.
   One-line fix: docker run -it --rm alpine /bin/sh -c "exit 0"

5. Quick Checks

1. Situation: Container exits with code 0.
   Command to run: docker run -it --rm alpine /bin/echo "Hello World"
   What a correct response looks like: 0

2. Situation: Container exits with code 1.
   Command to run: docker run -it --rm alpine /bin/false
   What a correct response looks like: 1

3. Situation: Container exits with code 125.
   Command to run: docker run -it --rm alpine /bin/sh -c "exit 125"
   What a correct response looks like: 125

6. Last-Minute Reference

• Docker exit codes are based on the container's exit status.
• Exit code 0 means the container exited successfully.
• Exit code 1 means the container exited with a non-zero status.
• Exit code 125 means the container was killed by a signal.
• Exit code 126 means the container was killed by a signal due to a missing command.
• Exit code 127 means the container was killed by a signal due to a command not found.
• Exit code 128+n means the container was killed by a signal with number n.
• Exit code 137 means the container was killed due to a timeout.
• Exit code 143 means the container was killed due to a SIGTERM signal.
• ⚠️ Always check the Docker version with docker version to ensure compatibility.
• ⚠️ Use docker container prune to delete all stopped containers.
• ⚠️ Use docker system prune to delete all unused data.