2.4 Lab - The Docker Lifecycle

Introduction

This hands-on lab is designed to give you practical experience with managing the Docker container lifecycle. From creating and running containers to stopping, pausing, and ultimately removing them, this lab will guide you through each stage using Docker CLI commands. By working directly in a Linux environment and utilizing the Nano editor for any file editing needs, you'll gain firsthand experience with the operational aspects of Docker containers.

Objectives

• Understand how to create and run Docker containers.
• Learn to inspect, stop, pause, and resume containers.
• Practice removing containers from the Docker host.

Lab Steps

Step 1: Preparing Your Environment

• Ensure Docker is installed on your Linux system. Open a terminal to execute Docker commands.
• Verify Docker installation: docker --version

Step 2: Creating and Running a Container

• Pull the latest nginx image from Docker Hub:

docker pull nginx:latest

• Run an nginx container in detached mode:

docker run -d --name my-nginx nginx:latest

• List running containers to confirm:

docker ps

You should see output like the following:

CONTAINER ID   IMAGE          COMMAND                  CREATED         STATUS         PORTS     NAMES
a95c1ed230d6   nginx:latest   "/docker-entrypoint.…"   7 seconds ago   Up 5 seconds   80

Step 3: Inspecting a Container

• Inspect the running container to view its configuration and state:

docker inspect my-nginx

You will see a lot of detail about the container.

• Use Nano to open a text file and note down some details from the inspection output for later reference: nano inspection-notes.txt

Step 4: Accessing Container Logs

• View the nginx container logs to confirm it's serving requests:

docker logs my-nginx

You should see output like the following:

/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Sourcing /docker-entrypoint.d/15-local-resolvers.envsh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2024/02/10 20:40:15 [notice] 1#1: using the "epoll" event method
2024/02/10 20:40:15 [notice] 1#1: nginx/1.25.3
2024/02/10 20:40:15 [notice] 1#1: built by gcc 12.2.0 (Debian 12.2.0-14) 
2024/02/10 20:40:15 [notice] 1#1: OS: Linux 6.2.0-1016-aws
2024/02/10 20:40:15 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2024/02/10 20:40:15 [notice] 1#1: start worker processes
2024/02/10 20:40:15 [notice] 1#1: start worker process 83
2024/02/10 20:40:15 [notice] 1#1: start worker process 84

Step 5: Pausing and Resuming the Container

• Pause the running container:

docker pause my-nginx

• Check the status of the container (should be paused):

docker ps

• Resume the container:

docker unpause my-nginx

• Verify it's running again:

docker ps

You should see output like the following:

CONTAINER ID   IMAGE          COMMAND                  CREATED         STATUS         PORTS     NAMES
a95c1ed230d6   nginx:latest   "/docker-entrypoint.…"   7 seconds ago   Up 5 seconds   80/tcp    my-nginx

Step 6: Stopping and Removing the Container

• Stop the running container:

docker stop my-nginx

• Remove the stopped container:

docker rm my-nginx

• List all containers to ensure it's removed (the list should be empty or not include my-nginx):

docker ps -a

Summary

In this lab, you've successfully navigated through the key stages of the Docker container lifecycle. Starting with pulling an image and running it as a container, you've learned how to inspect containers to understand their configuration and state. You've also gained experience with managing container states by pausing and resuming a container, and you've practiced cleaning up by stopping and removing a container. These skills are foundational for anyone working with Docker, providing the ability to manage containers effectively. Through hands-on experience, this lab has reinforced the importance of understanding the Docker lifecycle for efficient container orchestration and resource management.