How to Get Docker Logs

Docker logs may be used to observe and troubleshoot applications running inside of Docker containers. With access to these logs, developers may troubleshoot issues, understand application behavior, and ensure everything is functioning as it should. This article will provide a detailed explanation of how to appropriately read Docker logs.

Primary Terminologies

• Docker: A platform for applications that makes managing, scaling, and deploying programs inside containers easier.
• Container: A small, portable, self-contained environment that includes the application and all of its dependencies.
• Logs: Recorded output from programs, typically used for debugging and monitoring.
• Container ID: A unique number linked to every Docker container.
• Container Name: An easily recognizable name in human language that is linked to a Docker container.

Step-by-Step Process to Get Docker Logs

Step 1: Identify the Container

This command will list every container that is currently operating on the Docker system:

docker ps

With the help of this command, we can able to see a list of running containers with their IDs, names, and other details.

Step 2: Retrieve Logs from a Specific Container

After identifying the container, we will use the docker logs command to extract the logs. For that, we will utilize the container ID or name.

docker logs [OPTIONS] CONTAINER

• CONTAINER: The container ID or name.
• [OPTIONS]: Various options to filter or format the logs.

To get logs from a container, run:

docker logs <container-id-or-name>

Replace <container-id-or-name> with the actual ID or name of your container.

Step 3: Use Options to Filter or Format Logs

Docker provides several options based on the demands of the user or programmers to let them get certain logs.

Tail Logs

With the help of this command we can able to see last few lines of logs:

docker logs --tail <number-of-lines> <container-id-or-name>

Replace <number-of-lines> with the number of log lines you want to see.

Follow Logs

To continuously stream logs (similar to tail -f in Linux):

docker logs -f <container-id-or-name>

This command will keep the log output open and display new log entries in real-time.

Timestamp Logs

Using this command will add a timestamp to every log item:

docker logs -t <container-id-or-name>

Retrieve Logs Since a Specific Time:

With the help of this command we can get logs since a specific time:

docker logs --since <timestamp> <container-id-or-name>

Replace <timestamp> with a time value (e.g., 2024-06-06T00:00:00).

Let’s see the all process with the help of an example:

Step 1: Pull the nginx Image

With the help of this following we will pull the nginx Image.

Step 2: Run the nginx Image

With the help of this following we will run the nginx Image.

Step 3: Retrieve Logs from the Hello-World Container

With the help of this command we can able to get the logs assosicated with the container name:

Basic Logs:

Tail Logs:

Follow Logs:

Timestamp Logs:

Docker log management is necessary to track and diagnose issues with your programs. In order to solve issues, ensure application performance, and maintain system integrity, good log management is crucial. We used the nginx image as an example to show how to activate Docker logging in a straightforward manner. We showed how to acquire the image from Docker Hub, start the container, and collect logs using a range of Docker commands. Among the features are simple log retrieval, real-time log following, and filtering logs according to time and line count. Learning these commands gives you the ability to manage and troubleshoot your Docker containers in an efficient manner, ensuring that your applications run smoothly and that issues are resolved promptly.

Can a halted container provide logs?

Yes, both stopped and active containers may use the docker logs command.

How can I see real-time log streaming?

You can stream logs from a Docker container in real-time using the docker logs -f <container-name> command.

Can I use time to filter logs?

The –since and –until options in Docker allow you to filter logs according to a time range.

Where are the logs from Docker kept?

{/var/lib/docker/containers/<container-id>/} is where they are kept.

What happens if I try to obtain logs and the container is not running?

You can get logs from stopped and operating containers with Docker. As long as the container is running, the docker logs command functions