How to Fix Docker CrashLoopBackOff on Debian 11

For WebToolsWiz.com, here’s a direct guide to troubleshooting “Docker CrashLoopBackOff” on Debian 11.

Fixing Docker CrashLoopBackOff on Debian 11

1. The Root Cause “Docker CrashLoopBackOff” on Debian 11 signifies that a container’s primary process repeatedly fails to start successfully, exiting with a non-zero status code. This behavior commonly points to an application-level error within the container, or underlying Docker daemon issues such as resource exhaustion or network misconfiguration on the host system.

2. Quick Fix (CLI) Execute these commands to diagnose and resolve common transient issues:

  1. Examine Container Logs: Identify the immediate cause of the container’s crash. 
    sudo docker logs <container_name_or_id>
  2. Restart Docker Daemon: Clear any transient daemon-level issues and reset Docker’s state. 
    sudo systemctl restart docker
  3. Clean Up Resources (Optional): Free up disk space and system resources by removing stopped containers, unused images, and volumes. 
    sudo docker system prune -f
  4. Attempt Container Restart: Try to start your container again. 
    sudo docker start <container_name_or_id>
# Or, if using docker-compose:
# sudo docker-compose up -d

3. Configuration Check Edit the Docker daemon configuration file /etc/docker/daemon.json to ensure robust operation, specifically focusing on stable DNS resolution and preventing excessive log file growth during repeated crashes.

Add or modify the following content:

{
  "dns": ["8.8.8.8", "8.8.4.4"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  }
}

If the file does not exist, create it. This configuration ensures containers use reliable public DNS resolvers and limits the size and number of log files. After modifying the file, restart the Docker daemon for changes to take effect:

sudo systemctl restart docker

4. Verification Confirm the Docker daemon is running correctly and your container is now in a healthy state.

  1. Check Docker Daemon Status: 
    sudo systemctl status docker
    Verify the output shows Active: active (running).
  2. Verify Container Status: 
    sudo docker ps
    Ensure your problematic container is now listed with a Status indicating it is Up and running stably (e.g., Up X seconds).
  3. Review New Logs (if still crashing): If the container continues to crash, review its latest logs for updated error messages. 
    sudo docker logs <container_name_or_id>

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