Docker 102

Roughly 6 minutes to read; Viewed 2 times
Part of a (short) series on 'knowing enough to be dangerous' with Docker.

John discusses various aspects of Docker in this video, including networking within containers, Docker Compose, troubleshooting Docker Compose, passing environment variables, running containers using Docker Compose, mounting volumes, and security issues. They provide explanations, examples, and demonstrations to help viewers understand and apply these concepts. John also emphasizes the benefits of using Docker, such as simplifying the process of running multiple containers together and reducing administration overhead. They conclude by offering to answer any questions from the audience.

00:00:00 In this section, John discusses the basic concepts of Docker and gives an overview of containerization and images. They also touch on networking within containers, including different ways to configure networking and the concept of isolation. John mentions that there are ways to poke holes in containers, particularly through networking and storage devices. They then dive deeper into networking concepts, including options such as none, host mode, bridge mode, and overlay mode. The focus is primarily on bridge mode, which is used for a single host.

00:05:00 In this section, John explains the differences between bridge mode and overlay mode in Docker networking. Bridge mode is the default mode, where containers have a connection to the host and can connect to the outside world through Network Address Translation (NAT). However, by default, connections cannot be initiated from the outside world to the container. To allow incoming connections, port forwarding can be used. Overlay mode, on the other hand, is used in container orchestrators like Swarm, where containers running on different hosts can communicate with each other as if they were in bridge mode. This mode is commonly used in web applications where multiple containers need to serve web pages or web sockets. To handle multiple containers on the same port, a reverse proxy like Nginx is used to translate incoming connections to the appropriate container. This pattern is becoming more common in small setups, replacing the need for separate VMs for each website. However, when using port forwarding, it is important to be cautious as it opens the container to all connections.

00:10:00 In this section, John discusses Docker compose, which is a tool used to describe the arrangement of containers and pass along configurations in a repeatable way. Docker compose is based on yaml files and John provides an example of a Docker compose file. The file includes a version at the top level and a Services block, which lists the containers to be run. John explains the different configurations for a container, such as the image, restart policy, and environment variables. Overall, Docker compose simplifies the process of running multiple containers together.

00:15:00 In this section, John explains how to set up another instance using Docker Compose for PHP my admin. They specify the container name, image, and restart setting. To allow external interface, they open the port and set an environment variable. They also add a “depends on” stanza to ensure that PHP my admin only starts if there is a database to connect to. John demonstrates how to run the Docker Compose command and explains that the PHP my admin container has a complex image with various web configurations. The process involves downloading and eventually completing the setup.

00:20:00 In this section, John and the audience members are troubleshooting issues with Docker Compose while trying to run a demo. They discuss possible solutions, such as checking file names and ensuring that Docker Compose is installed properly. The demo seems to be broken due to a typo in the Docker Compose file, causing the container to not start. Eventually, they discover that the root password needs to be modified for the MySQL container. Despite the challenges, they hope that the adjustments made will resolve the issues and allow for a successful demo.

00:25:00 In this section of the video, John discusses the progress of running the Docker containers and encountering some errors along the way. They mention the need to make some changes, such as adding quotes and being mindful of system updates and changes. Eventually, they are able to get the containers running successfully. They also explain how to check the running containers using the Docker PS command and note the mapping of ports. John then mentions the use of environment variables to pass parameters into the containers and explains the syntax and persistence of these variables. Finally, they highlight the need for a more streamlined and secure setup, suggesting the use of additional configuration options.

00:30:00 In this section, the video discusses how to pass environment variables to Docker containers using Docker Compose. By using the dollar bracket syntax in the YAML file, users can replace values with environment variables. This allows for flexibility and customization when running containers. In addition, the video explains how to set default values and error messages for environment variables. The example given shows how to replace a MySQL root password with an environment variable, ensuring that sensitive information is not exposed. The video also mentions the importance of securing containers by specifying the interface to listen to. Lastly, the video demonstrates how to specify environment variables for accessing PHPMyAdmin. Overall, this section provides useful information on how to manage environment variables in Docker Compose.

00:35:00 In this section of the video, John discusses how to run Docker compose commands to start containers and set passwords. They explain that running the containers in the background can be done by adding a “-d” flag to the command. They also mention the importance of binding the containers to only the host machine to prevent unauthorized access to the database. John then introduces the concept of mounting volumes to store data outside of the containers, specifically mentioning the ability to connect to remote stores like AWS. They explain that volumes can be set to read-only or read-write modes and provide an example of how to add a volume to the Docker compose file. Overall, this section focuses on the practical aspects of running and managing containers in Docker.

00:40:00 In this section, John discusses the different ways to mount volumes in Docker. They mention that bind mounts are the most common for development purposes since they allow connecting to files on the host machine. However, for orchestrated larger networks with multiple hosts, it is important to consult the hosts to see how they want volumes to be mounted. John also introduces the concept of Docker volumes, which are managed by Docker itself and can be shared between containers. They briefly touch on the benefits of using volumes and mention that they can be explored further at a later time. Finally, John provides instructions on how to set up a folder for data using Docker Compose and verifies that the data persists even after stopping and starting the containers. They encourage further exploration of Docker images on Docker Hub and recommend looking at the Docker Compose reference for more in-depth guidance.

00:45:00 In this section, John discusses security issues with outdated virtual machines (VMs) and the need for container templates for common configurations. They mention the goal of having a ready-made website integrated with gitlab, allowing users to easily copy a repository and have it built and deployed seamlessly. This approach is intended to reduce the administration overhead associated with VMs. John concludes by expressing gratitude for the audience’s attention and offering to answer any questions.

Summary text originally from with light post editing.