How to view specific logs after entering docker

As Docker becomes more popular, developers and system administrators start using it to deploy and manage applications. However, it's not uncommon for problems to arise when using Docker. In order to solve the problem, we usually need to look at the logs of the Docker container. So, how to view specific logs after entering Docker?

The following are some methods:

1. Use the docker logs command

Docker provides a very simple way to view the logs of the container, which is to use the docker logs command.

Syntax:

docker logs [OPTIONS] CONTAINER_NAME/CONTAINER_ID

Example:

docker logs -f CONTAINER_NAME

-f option can track the log output of the container in real time.

2. Use the docker-compose logs command

If you use docker-compose to manage multiple containers, then you can use the docker-compose logs command to view the logs of the container.

Syntax:

docker-compose logs [OPTIONS] CONTAINER_NAME

Example:

docker-compose logs -f CONTAINER_NAME

-f option can track the log output of the container in real time.

3. Use container log mounting

You can also mount the log file in the container to the host, and then view the log file directly.

Syntax:

docker run -d --name CONTAINER_NAME -v HOST_LOG_PATH:CONTAINER_LOG_PATH IMAGE_NAME

Example:

docker run -d --name app -v /var/log/app:/var/log/app app-image

The -v parameter here can mount the /var/log/app directory in the container to /var/ on the host log/app directory.

Then, use the tail command on the host to view the output of the log file:

tail -f /var/log/app/app.log

4. Use third-party tools

In addition to the tools that come with Docker, There are many third-party tools that can help us view the logs of containers. Probably the most popular of these is the ELK (Elasticsearch, Logstash, and Kibana) stack, which is an open source log management tool. Using the ELK stack, you can easily collect, store, and visualize container logs.

Conclusion

Viewing the container's logs in Docker may be the first step in solving the problem. The docker logs command and docker-compose logs command provided by Docker are very easy to use. If you need more advanced log management and analysis capabilities, you need to use third-party tools.

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