How to fix Container process (PID 1) exited unexpectedly in Docker

# View full logs from exited container
docker logs <container_name_or_id>

# View last 50 lines with timestamps
docker logs --tail 50 --timestamps <container_name_or_id>

# Follow logs in real-time (useful during debugging)
docker logs -f <container_name_or_id>

# Get detailed container state including exit code
docker inspect --format='{{.State.ExitCode}} {{.State.Error}}' <container_id>

# Get full state information
docker inspect --format='{{json .State}}' <container_id> | jq

docker inspect --format='{{.State.OOMKilled}}' <container_id>

CMD python app.py
# This runs: /bin/sh -c "python app.py"
# /bin/sh is PID 1, python is a child process

CMD ["python", "app.py"]
# This runs: python app.py directly as PID 1
# Python receives signals directly

# Nginx - use daemon off
CMD ["nginx", "-g", "daemon off;"]

# Apache httpd - use FOREGROUND
CMD ["httpd", "-D", "FOREGROUND"]

# PostgreSQL - runs in foreground by default
CMD ["postgres"]

# Redis - runs in foreground by default
CMD ["redis-server"]

# Node.js - runs in foreground by default
CMD ["node", "server.js"]

# BAD - backgrounds the process
CMD ["sh", "-c", "nginx &"]

# BAD - nohup often causes issues
CMD ["nohup", "python", "app.py"]

#!/bin/bash
# Setup tasks
echo "Starting application..."
python app.py &  # BAD: backgrounds the process
echo "Started"    # Script exits here, container stops

#!/bin/bash
set -e

# Setup tasks (run before main process)
echo "Running initialization..."

# Use exec to replace shell with the main process
# Now python becomes PID 1 and receives signals directly
exec python app.py

# Run container with init process
docker run --init -d myimage

# In docker-compose.yml
services:
  myapp:
    image: myimage
    init: true

# Install tini
RUN apt-get update && apt-get install -y tini

# Use tini as entrypoint
ENTRYPOINT ["/usr/bin/tini", "--"]
CMD ["python", "app.py"]

import signal
import sys

def handle_sigterm(signum, frame):
    print("Received SIGTERM, shutting down gracefully...")
    # Cleanup code here
    sys.exit(0)

signal.signal(signal.SIGTERM, handle_sigterm)
signal.signal(signal.SIGINT, handle_sigterm)

# Your main application code

process.on('SIGTERM', () => {
  console.log('Received SIGTERM, shutting down gracefully...');
  // Cleanup code here
  process.exit(0);
});

process.on('SIGINT', () => {
  console.log('Received SIGINT, shutting down gracefully...');
  process.exit(0);
});

#!/bin/bash
trap 'echo "Caught SIGTERM"; exit 0' TERM
trap 'echo "Caught SIGINT"; exit 0' INT

# Your main logic here
while true; do
  # Do work
  sleep 1
done

# Override entrypoint to get a shell
docker run -it --entrypoint /bin/sh myimage

# Or /bin/bash if available
docker run -it --entrypoint /bin/bash myimage

# Once inside, manually run your application
./entrypoint.sh
# or
python app.py

# Keep container running with tail
docker run -d myimage tail -f /dev/null

# Then exec into it
docker exec -it <container_id> /bin/sh

# Check if container was OOM killed
docker inspect --format='{{.State.OOMKilled}}' <container_id>

# Check kernel logs for OOM messages (on the host)
dmesg | grep -i "killed process"

docker run -m 2g myimage

# docker-compose.yml
services:
  myapp:
    image: myimage
    deploy:
      resources:
        limits:
          memory: 2G

docker run -m 1g --memory-swap 2g myimage