How to redirect Docker logs to file?

To redirect Docker container logs to a file, you can use the --log-driver and --log-opt options when running the container. Docker provides several logging drivers, and you can choose one that suits your needs. The most commonly used logging drivers are json-file (the default), syslog, and journald. Here's how you can redirect Docker logs to a file using the json-file logging driver:

1. Create a Docker Container with Redirected Logs

This will run the container with the json-file logging driver and redirect the container's logs to files. The logs will be stored in the /var/lib/docker/containers/container_id/container_id-json.log file on the host, where container_id is the unique ID of your container.

docker run -d --name your_container_name \
  --log-driver=json-file \
  --log-opt max-size=10m \
  --log-opt max-file=3 \
  your_image_name

Explanation:

• d: Run the container in detached mode (in the background).
• -name your_container_name: Give a name to the container.
• -log-driver=json-file: Use the json-file logging driver to redirect logs to files.
• -log-opt max-size=10m: Set the maximum size of each log file to 10 megabytes (adjust as needed).
• -log-opt max-file=3: Set the maximum number of log files to rotate before removing old logs (adjust as needed).
• your_image_name: Replace this with the name of the Docker image you want to run in the container.

2. View the Logs

To view the logs of the running container, you can use the docker logs command:

docker logs your_container_name

This will display the logs on the console.

If you want to save the logs to a file on your host system, you can use output redirection:

docker logs your_container_name > container_logs.txt

This will save the container logs to the container_logs.txt file on your host system.

Remember to adjust the logging driver and options according to your requirements. Other logging drivers, such as syslog or journald, are also available and might be more suitable for specific use cases. The json-file driver is commonly used for redirecting logs to files when you want to keep the logs outside of Docker's default logging mechanism.

To learn more about logging, visit Better Stack Community.

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