Docker Commands Quiz
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Questions and Answers

What does the '-P' flag do in the 'docker run' command?

  • Lists all available images
  • Exposes a specific port in the container to the host (correct)
  • Runs the container in detached mode
  • Stops a running container

    • Which command is used to build a custom image from a 'Dockerfile' located in the current path?

  • docker volume create ex_volume
  • docker run -d -p 80:80 --name myapp2_nginx -v myapp2_nginx_volume:/usr/share/nginx/html issrcourses/myapp2:2.1
  • docker build -t myapp (correct)
  • docker images

    • What does the 'docker ps' command do?

  • Creates a new container
  • Shows all available containers
  • Removes a container
  • Shows running containers (correct)

    • Which command is used to import a container from a file?

    <p>docker import myapp.tar myappnew</p> Signup and view all the answers

    What does the '-i' flag do in the 'docker exec' command?

    <p>Creates an interactive session</p> Signup and view all the answers

    How can a volume 'ex_volume' be removed in Docker?

    <p>docker volume rm ex_volume</p> Signup and view all the answers

    What happens when the 'container_name' option is used when deploying a stack in swarm mode?

    <p>The container is prevented from restarting in case of a failure.</p> Signup and view all the answers

    How does setting 'stdin_open: true' affect the container behavior?

    <p>Allows attaching to the container interactively even when detached.</p> Signup and view all the answers

    In which scenario is the 'restart' option ignored?

    <p>When deploying services with shared volumes.</p> Signup and view all the answers

    What is the purpose of defining shared volumes at the same level of services?

    <p>To facilitate reuse across multiple services.</p> Signup and view all the answers

    What does 'depends_on' specify in the context of service configuration?

    <p>Services that the current service depends on.</p> Signup and view all the answers

    What is the purpose of setting networks like 'react-express', 'express-mongo' in the closing networks section?

    <p>To indicate which network containers should connect to during build.</p> Signup and view all the answers

    What is the purpose of the '-d' flag in 'docker compose up -d' command?

    <p>To create the container if it doesn't exist and start it in detached mode</p> Signup and view all the answers

    What does 'docker compose build' command do?

    <p>Builds or rebuilds services defined in the docker-compose.yml for updating changes in the Dockerfile</p> Signup and view all the answers

    What is the purpose of the 'COPY src/html /usr/share/nginx/html' instruction in a Dockerfile?

    <p>Copy from a folder path to a container path</p> Signup and view all the answers

    What does 'docker compose pull' command do?

    <p>Pulls images defined in the docker-compose.yml for updating images before starting or rebuilding containers</p> Signup and view all the answers

    What is the purpose of 'EXPOSE 80' instruction in a Dockerfile?

    <p>Make Port 80 available</p> Signup and view all the answers

    What does the 'image: webapp:1.1' line indicate in a Compose file?

    <p>Indicates an image named 'webapp' with tag '1.1'</p> Signup and view all the answers

    What is the purpose of defining 'none' for the network for isolation of services in Docker Compose files?

    <p>To isolate a service by not linking it to any network</p> Signup and view all the answers

    How can environment variables in Docker Compose files be beneficial to developers?

    <p>To securely pass sensitive information to containers</p> Signup and view all the answers

    What is the purpose of the 'healthcheck' section in Docker Compose files?

    <p>To check if the container is running healthily</p> Signup and view all the answers

    What does the 'retries' parameter under 'healthcheck' in Docker Compose files refer to?

    <p>The number of retries to attempt before considering a health check failed</p> Signup and view all the answers

    How does defining 'host' under networks in a Docker Compose file affect a container?

    <p>It allows the container to connect to the external server host network</p> Signup and view all the answers

    Why is defining environment variables important in a containerized application?

    <p>To securely pass sensitive information to containers</p> Signup and view all the answers

    Study Notes

    Docker Commands and Flags

    • The -P flag in the docker run command automatically publishes all exposed ports to random ports on the host system.
    • Building a custom image from a Dockerfile in the current path is done using the command docker build ..
    • The docker ps command lists all running containers along with their IDs, names, and status.
    • To import a container from a file, use the docker import command.
    • The -i flag in the docker exec command allows interactive mode, keeping the standard input (stdin) open for the container.

    Managing Volumes and Containers

    • To remove a volume named ex_volume, the command docker volume rm ex_volume is used.
    • When deploying a stack in swarm mode, the container_name option sets a specific name for the container, ensuring it is consistent across deployments.
    • Setting stdin_open: true allows the container to accept interactive input, which can be useful for applications needing terminal input.

    Service Dependencies and Configuration

    • The restart option is ignored if the container is stopped manually (e.g., using docker stop).
    • Defining shared volumes at the same service level allows easy data sharing and persistence between multiple containers.
    • The depends_on directive specifies service dependencies, ensuring that the listed services are started in the correct order during deployment.

    Networking and Isolation

    • Defining networks, such as react-express and express-mongo, in the closing networks section isolates services while allowing communication between those specified services.
    • The -d flag in the docker compose up -d command runs containers in detached mode, allowing them to run in the background.

    Dockerfile Instructions and Environment Configuration

    • The command docker compose build is used to build images as specified in the docker-compose.yml file.
    • The instruction COPY src/html /usr/share/nginx/html in a Dockerfile copies HTML files from the source directory into the NGINX container.
    • The docker compose pull command retrieves the latest images for services defined in the docker-compose.yml file from the remote registry.
    • The EXPOSE 80 instruction in a Dockerfile indicates that the container listens on port 80 at runtime.

    Compose Configuration and Health Checks

    • The image: webapp:1.1 line in a Compose file specifies the Docker image to use for a service, with the version label 1.1.
    • Defining none for the network facilitates service isolation, ensuring that the services do not share any networking stack.
    • Environment variables in Docker Compose files enable customization of service configurations and behaviors easily, providing flexibility to developers.

    Health Checks and Networking

    • The healthcheck section in Docker Compose files is used to define a way to check if a container is healthy and properly running.
    • The retries parameter under healthcheck refers to the number of consecutive failures allowed before considering the container as unhealthy.
    • Specifying host under networks in a Docker Compose file allows containers to use the host's networking stack, providing them access to the host network interfaces.
    • Defining environment variables is crucial in containerized applications as it promotes configurability and aids in maintaining different settings across development and production environments.

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    Description

    Test your knowledge of Docker commands with this quiz covering topics like pulling and pushing images, building custom images, viewing images data, and more.

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