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Questions and Answers
Which command is used to build a Docker image?
Which command is used to build a Docker image?
A container can be created without an image.
A container can be created without an image.
False
What is a Dockerfile used for?
What is a Dockerfile used for?
To automate the process of Docker image creation.
An image in Docker contains executable application source code as well as all the necessary ______ required to run the application.
An image in Docker contains executable application source code as well as all the necessary ______ required to run the application.
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Match the following Docker commands with their functions:
Match the following Docker commands with their functions:
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What is the primary purpose of a Docker image?
What is the primary purpose of a Docker image?
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Docker containers have access to all files on the host machine.
Docker containers have access to all files on the host machine.
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Which base image is used in the example Dockerfile for the toy.py app?
Which base image is used in the example Dockerfile for the toy.py app?
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What is the purpose of a Dockerfile?
What is the purpose of a Dockerfile?
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Containers have a shared file system that allows for modification by any container using the same image.
Containers have a shared file system that allows for modification by any container using the same image.
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What layer of the file system contains modifications made by a container?
What layer of the file system contains modifications made by a container?
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Docker images are built using a ______________ file system.
Docker images are built using a ______________ file system.
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Match the following components of Docker with their descriptions:
Match the following components of Docker with their descriptions:
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Which of the following is NOT a benefit of using Docker containers?
Which of the following is NOT a benefit of using Docker containers?
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The metadata of a Docker image includes information like exposed ports and environment variables.
The metadata of a Docker image includes information like exposed ports and environment variables.
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What allows for easy modification of existing images in Docker?
What allows for easy modification of existing images in Docker?
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What is the purpose of the command 'RUN pip install Flask' in a Dockerfile?
What is the purpose of the command 'RUN pip install Flask' in a Dockerfile?
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The command 'EXPOSE 8001' indicates that the container should listen on port 8001.
The command 'EXPOSE 8001' indicates that the container should listen on port 8001.
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What environment variable is set to indicate the main application file in this Dockerfile?
What environment variable is set to indicate the main application file in this Dockerfile?
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The command 'CMD ["flask", "run", "--host=0.0.0.0"]' is used to ________.
The command 'CMD ["flask", "run", "--host=0.0.0.0"]' is used to ________.
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Match the Dockerfile command with its function:
Match the Dockerfile command with its function:
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What does the 'COPY toys.py' command do?
What does the 'COPY toys.py' command do?
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The container's working directory is set to './app' using the WORKDIR instruction.
The container's working directory is set to './app' using the WORKDIR instruction.
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What command does the Dockerfile execute when the container starts?
What command does the Dockerfile execute when the container starts?
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What is Docker Hub primarily used for?
What is Docker Hub primarily used for?
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A Docker registry can only hold public images.
A Docker registry can only hold public images.
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What command is used to push an image to a Docker registry?
What command is used to push an image to a Docker registry?
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Docker images are organized in a Docker ______ which holds all the versions of a specific image.
Docker images are organized in a Docker ______ which holds all the versions of a specific image.
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Match the following Docker concepts with their descriptions:
Match the following Docker concepts with their descriptions:
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Which of the following is a true statement about Docker Engine?
Which of the following is a true statement about Docker Engine?
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Docker is configured to look for images on Docker Hub by default.
Docker is configured to look for images on Docker Hub by default.
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What is the purpose of data volumes in Docker?
What is the purpose of data volumes in Docker?
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What is a benefit of using Docker for CI/CD processes?
What is a benefit of using Docker for CI/CD processes?
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Docker always prevents dependency conflicts when importing multiple packages into a single container.
Docker always prevents dependency conflicts when importing multiple packages into a single container.
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What is a common command used to start services in Docker Compose?
What is a common command used to start services in Docker Compose?
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Docker containers are designed to have a __________ responsibility and use a few integrated packages.
Docker containers are designed to have a __________ responsibility and use a few integrated packages.
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What might happen if you update a Dockerfile based on an image tagged 'latest'?
What might happen if you update a Dockerfile based on an image tagged 'latest'?
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Using the latest version of packages in Docker images guarantees that all vulnerabilities are patched.
Using the latest version of packages in Docker images guarantees that all vulnerabilities are patched.
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Name one reason why dependency conflicts can occur in Docker containers.
Name one reason why dependency conflicts can occur in Docker containers.
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What does the --publish (-p) flag do in Docker commands?
What does the --publish (-p) flag do in Docker commands?
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Docker containers have their own isolated file system and do not have access to the host's file system.
Docker containers have their own isolated file system and do not have access to the host's file system.
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What is the primary purpose of tagging a Docker image?
What is the primary purpose of tagging a Docker image?
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A unique ID is assigned to every ______ created in Docker.
A unique ID is assigned to every ______ created in Docker.
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Which command would you use to list all existing Docker images in the local registry?
Which command would you use to list all existing Docker images in the local registry?
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A Docker container can be created without specifying a Docker image.
A Docker container can be created without specifying a Docker image.
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What is the significance of using a unique prefix for an image ID in Docker commands?
What is the significance of using a unique prefix for an image ID in Docker commands?
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Study Notes
Topic 3: Containers - Part 1
- These slides are the property of Dr. Daniel Yellin and intended for use only by students in the class. Distribution or posting is prohibited.
Docker Overview
- Docker, a tool for packaging, managing, and deploying software applications, is based on images, containers, and layers.
- It addresses the challenge of packaging all software dependencies together and resolving conflicts that may arise when multiple applications or modules need to run on a single computer if those applications are using different versions of the same package(s).
What Problems does Docker Solve?
- Packaging: Bundling the application with all required dependencies into a single unit called a container. This isolates the application from the host environment and ensures consistent execution across different systems.
- Portability: Allowing applications to run in various environments (development, testing, and production) regardless of hardware, operating system, or configuration.
- Independent Lifecycles: Enabling the deployment and updating of application modules independently, without impacting the entire application.
Multiple Programs Running on top of OS
- Diagrams explain how Docker's containers create isolated environments separated from the operating system's kernel.
- Running different versions of software on one machine is possible without conflicts using isolated containers.
A Container Partitions System Resources
- Containers isolate different applications using system resource partitioning, so different applications inside different containers cannot interact.
What problems does Docker solve? — Portability
- Applications frequently need to run in various environments (desktop, testing, production, cloud).
- Docker addresses compatibility problems that emerge from different hardware and operating systems by facilitating the transport and deployment of applications without altering different version specificities for each one.
- Docker can run multiple applications on the same server despite differing operating systems and hardware requirements.
Heterogeneous Applications
- Applications built using differing hardware and/or operating systems can run on a single server (given same kernel). This is possible as long as the respective packages are also consistent.
What problems does Docker solve? — Independent lifecycle management of application modules
- Docker enables an independent lifecycle management for different application parts or modules.
- When a bug is fixed or a feature added to a single module these changes can be deployed without impacting other parts of the application.
- This promotes modularity (and single-responsibility principle) and facilitates updating and testing individual parts of the application.
Independent lifecycle management — Example
- Diagram showing the different team deployment stages and how this approach is effective in managing multiple-module applications.
What problems does Docker solve? — Sharing and reusability
- Reusing code and resources can be complex due to installation processes, error-prone build processes, and various dependencies.
- Docker simplifies code reuse by allowing the packaging and distribution of applications (and the dependencies) without the need for the end-user to unpack/re-install or reconfigure multiple packages.
- Using Docker, others can take code and update it without negatively impacting the original source code.
What problems does Docker solve? — Scalability
- Docker is a solution for scaling applications by increasing server instances (given adequate capacity) to handle the increased flow of requests. This approach can reduce costs on cloud hardware and VMs.
Docker bridges development and deployment
- Docker encapsulates code and dependencies. It facilitates quick, reliable, and portable applications (across operating systems) leveraging container engine services.
- Different teams can build and deploy their parts, ensuring effective coordination.
- Automating configuration and updates via pipelines simplifies deployment processes.
Images
- Images are collections of files, metadata, and a command. These contain executable application code, tools, libraries, and dependencies.
- They are templates to create containers.
Images and Containers
- Containers are isolated runtime processes based on images.
- The command, files, and metadata are accessed for the process execution.
- The process properties are defined in metadata, such as accessible network ports.
Dockerfiles
- Dockerfiles are used to automate image creation process using a syntax and commands to build images.
- These files list instructions for building images.
- The image generation can be based on other images, using a syntax for "on-top" image construction.
Docker by example
- Docker provides a method for building images using images, container management, and container execution.
4 Docker Commands
- Summary of Docker commands, including build, run, images, and ps.
A Dockerfile to containerize our toy.py app
- Detailed Dockerfile instructions for packaging the toy.py application. This includes the use of FROM (to use a base image), WORKDIR to create an app directory on the image, COPY command used to copy files and RUN to execute a shell command on the image.
- The EXPOSE command, for exposing the port 8001 in the container, is also included.
Dockerfile: Instructions on Making an Image
- Detailed Dockerfile instructions with explanations for building a Docker image.
Dockerfile: Instructions on Making an Image (detail)
- Detailed instructions on building a Docker image with explanations for each command.
Build Image
- How to build the image, specifying the name and tag “toysimage:v1”
- Identifying/Locating the Dockerfile.
Explaining the docker build cmd messages
- Explanation of the detailed process of building an image to be used as a container
Docker images
- Finding Docker images in local image repositories using commands (to list images).
Dockerfiles and layers
- How instructions in Dockerfiles create layers for an image
- Layer contents are encoded by the Dockerfile execution instructions.
- Other instructions modify image metadata.
Layers in the toys container
- Visualization of how layers combine/form the whole image
Looking inside an image
- Exploring the software content/vulnerabilities using Docker SBOM command.
Docker Desktop, CVE Vulnerabilities
- Showing vulnerabilities in each image layer.
4 Docker Commands(page 28)
- Review of Docker commands for building images, running images, listing images
Create and run container
- Instructions for creating and running a container using Docker commands and command parameters
Ports and port forwarding
- Defining ports as numeric identifiers for connecting software and services.
- Describing port forwarding/mapping as translating network traffic requests.
Docker containers have their own IP addresses and ports
- Containers have their own IP addresses (changing during re-start).
- Containers listen on specific ports, such as 8001 for HTTP requests (API calls).
- Clients use the host's IP address and the published port to interact with the container.
Port publishing
- How to publish container ports to the host's port(s).
- How communication works (client, host, container).
Port mapping in Docker
- How to map container ports to host ports (in case of multiple container instances).
Build and run container (cont)
- How to list running and all containers (running or stopped).
- Shows what port to use to forward requests to specific container ports
Checking that the server is running correctly
- How to issue requests to a RESTful server.
- How to use Postman or curl for this testing
Curl requests to toys server
- Examples of curl commands sending POST requests with various parameters (in JSON).
- Illustrates data sent to and received from the Docker container.
What does "docker run” really do?
- Detailed explanation of the docker run command: finding images, creating containers, mounting file systems, and starting processes.
Common container lifecycle commands
- Summary of common commands associated with container lifecycle (remove, stop, start, kill, pause, unpause).
Union File System
- How containers share and modify images (how different layers are combined in images with a "copy-on-write" system).
Union file system
- The Union File System helps manage how containers share and modify images by keeping contents separate.
Union file system
- Explanation of how the Union File System merges file systems while keeping the underlying structures distinct, enabling containers to share files.
- Shows diagrammatical view of how containers reuse layers of files when images are created or modified/augmented.
Copy-on-write
- How changes are recorded/isolated from the main image structure. This allows for multiple containers to use the same base image without over-writing each other.
Union file system helps avoid dependency conflicts
- Understanding how the union file system helps prevent compatibility issues by keeping dependencies isolated among containers
What we have learned about Docker so far
- Summarizing the key concepts of Docker images, containers, and Dockerfiles (the recipes used to create images).
What we have learned about Docker so far (cont)
- A Dockerfile is a recipe for making new images.
- Easy example using
rest-word-svr. - Docker has a rich set of commands
Question: Running two separate instances
- How to run two container instances and how to address them on different ports on the host machine.
Running two separate rest-word-svr instances
- Steps to run two instances of the Docker image,
toysimage:v1. - Explanation of how different containers can run parallelly, and how port publishing is essential for separate communication.
Running two separate rest-word-svr instances cont
- Instructions to verify the operation of two containers through different port addresses.
- The summary image shows the running status and mapping to different hostports
Issues requests (curl) to the two containers
- Examples of issuing HTTP requests to each of the container instances through the appropriate Docker Host ports, demonstrating that both are operating correctly.
Docker Architecture
- Description of the main components comprising Docker (host machine, client, daemon, REST API, and private registry).
Docker Architecture (cont)
- Detailing how the Docker client connects and interacts with Docker daemon, providing images, and executing instructions.
Docker Architecture
- Describing the overall structure of a Docker system.
Docker Engine provides a REST API
- Description of Docker RESTful APIs and available commands.
Registries and Repositories
- Docker registries, repositories, and artifacts. They store named images and each repository may have multiple versions of the same image.
Docker Hub and private registries
- Features of Docker Hub and the value of private registries for security and image management.
Docker best practices
- Best practices for efficiently building, deploying and managing containers: using single process per container, treat containers as ephemeral entities. use pre-built images to minimize the layers.
How to share using Docker
- Two contrasting approaches to sharing Docker images (public repository and Dockerfile sharing).
Docker Summary
- Summarizing the important characteristics of Docker as a tool for modern application deployment
Docker helps developers
- Summarizing the benefits and functionalities of Docker as a tool for developers.
But Docker does not solve all problems
- Issues/challenges when using Docker, including dependency and isolation problems, image vulnerabilities, potential conflicts.
Docker compose common commands
- Listing common Docker compose commands for managing containers, images, and volumes.
References
- Providing the list of resources used for this lesson. This includes the links (URLs) to articles, pages, books, and documents used to develop the lesson.
Additional reference material
- List of links containing additional resources to learn more about Docker. This should guide users seeking additional resources/information.
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Description
Test your knowledge of Docker with this quiz covering essential concepts such as images, containers, and Dockerfiles. Assess your understanding of command usage, file systems, and the purpose of Docker components. Perfect for beginners looking to solidify their Docker skills.
