How to View Docker Container Logs
Docker is a platform that allows you to create, run, and manage applications in a container. As containerized applications run in isolated environments, you may need to monitor them and sometimes troubleshoot issues. A container generates logs of activities and events. Docker collects the standard output (stdout) and standard error (stderr) streams from the main process running inside the container and makes them accessible through logging commands.
This article explains how to check the logs of Docker containers and Docker Compose services.
The Short Answer
Here is a list of the most commonly used commands to view logs in Docker.
Continue reading for detailed explanations and examples of each command.
View Container Logs
To view the logs of a container, you can use the docker container logs command. It shows all the container output written to stdout and stderr.
docker container logs Command Syntax
[OPTIONS]modify the command behavior.[CONTAINER]is the name or the ID of the container whose logs you want to see.
This command works for both running and stopped containers.
Command Options
Command Demonstration
Create and run a demo container based on the latest version of the
nginximage.CONSOLEThis command creates a container
test-appand starts it.Verify the container.
CONSOLEYou should see the
test-appcontainer listed in the output.View the logs of the container.
CONSOLEView logs with timestamps.
CONSOLEView only the last 10 lines of logs.
CONSOLEView logs from the last 5 minutes.
CONSOLEFollow the logs of the application container.
CONSOLEThe command shows existing logs and occupies the terminal while waiting for new entries. As the nginx container receives requests, new log entries appear in real-time.
View Logs from Docker Compose
Docker Compose applications run multiple connected services, each in its own container. You can view the logs of these services using the docker compose logs command.
docker compose logs Command Syntax
CONSOLE
[OPTIONS]modify the command behavior.[SERVICE...]is the optional service name. If omitted, the command shows logs from all services.
Command Options
Command Demonstration
Create a
docker-compose.yamlmanifest to define a multi-container Docker compose application.CONSOLEPaste the following contents.
YAMLSave and exit the manifest file.
This file creates a Docker application with the following three services:
web: It is a web server based on the latestnginximage. It maps the port8080on the host to the port80in the container and depends on theappservice to start first.app: It is a simple application based onnode:16-alpineimage. It runs a shell command that logs a message "App is running..." with timestamp every three seconds.database: It is a database service app based on thepostgres:13image. It's configured with a password and a database name through environment variables.
Start the services.
CONSOLEVerify the created containers.
CONSOLEYou should see a list of containers with the field
SERVICEindicating its service name.View logs from all services.
CONSOLEView logs from only the
webservice.CONSOLEView logs from multiple services.
CONSOLEFollow logs from a specific service with limited history.
CONSOLEView logs with timestamps and follow mode.
CONSOLECombine multiple options.
CONSOLEThis command shows logs from both the web and database services, showing timestamps, limiting to the last 20 lines, and only displaying logs from the past 5 minutes.
Conclusion
You have learned how to check the logs of Docker containers and Docker compose services. You can now view container logs using commands like docker container logs, follow live logs with the --follow option, and check logs of multi-container Docker compose services using docker compose logs. Visit the Docker Documentation for more information and advanced configuration options.
Tags:Docker
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