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 (C)</p> Signup and view all the answers

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

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

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

<p>docker volume rm ex_volume (A)</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. (A)</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. (D)</p> Signup and view all the answers

In which scenario is the 'restart' option ignored?

<p>When deploying services with shared volumes. (C)</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. (C)</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. (C)</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. (A)</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 (D)</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 (C)</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 (C)</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 (D)</p> Signup and view all the answers

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

<p>Make Port 80 available (B)</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' (B)</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 (C)</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 (B)</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 (D)</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 (D)</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 (A)</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 (B)</p> Signup and view all the answers

Flashcards

What does the -P flag do in docker run?

The -P flag automatically publishes all exposed ports from the container to random, unassigned ports on the host system.

How do you build a Docker image from a Dockerfile?

The command docker build . builds a Docker image from a Dockerfile located in the current working directory.

How do you list running Docker containers?

The command docker ps lists all running Docker containers, showing their IDs, names, and status.

How do you import a container image from a file?

The command docker import is used to import a container image from a file.

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What does the -i flag do in docker exec?

The -i flag in docker exec ensures the container's standard input (stdin) remains open, allowing interactive input from the host system.

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How do you remove a Docker volume named ex_volume?

The command docker volume rm ex_volume removes a volume named ex_volume.

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How do you ensure consistent container names in Docker Compose?

When using Docker Compose, the container_name option lets you specify a consistent name for your containers across deployments.

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Why is stdin_open: true useful in a Docker Compose service?

Setting stdin_open: true in Docker Compose allows the container to accept interactive input, which can be useful for applications needing user interaction from the terminal.

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When is the restart option in Docker Compose ignored?

The restart option in Docker Compose is ignored if a container is manually stopped (e.g., using docker stop).

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How do you easily share data between multiple containers in Docker Compose?

Defining shared volumes at the same service level in Docker Compose enables seamless sharing and persistence of data between multiple containers.

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How do you enforce service startup order in Docker Compose?

The depends_on directive in Docker Compose specifies dependencies between services, ensuring that services start in the correct order during deployment.

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How do networks help with isolation and communication in Docker Compose?

Defining networks in Docker Compose, like react-express and express-mongo, isolates services while allowing communication between those specified services.

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What does the -d flag do in docker compose up?

The -d flag in the command docker compose up -d launches containers in detached mode, allowing them to run in the background.

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How do you build images for services defined in docker-compose.yml?

The command docker compose build is used to build images for services defined in the docker-compose.yml file.

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What does the COPY instruction do in a Dockerfile?

The instruction COPY src/html /usr/share/nginx/html in a Dockerfile copies HTML files from the src/html directory to the Nginx container's html directory.

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How do you pull the latest images for services defined in docker-compose.yml?

The command docker compose pull retrieves the latest images for services specified in the docker-compose.yml file from the remote registry.

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What does the EXPOSE instruction do in a Dockerfile?

The instruction EXPOSE 80 in a Dockerfile indicates that the container will listen on port 80 at runtime.

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How do you specify the image and version for a service in Docker Compose?

The line image: webapp:1.1 in a Compose file specifies that the service should use the webapp image with the version 1.1.

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When would you define none for the network in Docker Compose?

Defining none for the network in Docker Compose ensures complete isolation of services, preventing any interaction between them.

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What is the purpose of environment variables in Docker Compose?

Environment variables in Docker Compose files allow flexible customization of service configurations, making deployments adaptable.

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What is the role of the healthcheck section in Docker Compose?

The healthcheck section in Docker Compose defines how to check if a container is healthy and running properly.

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What does the retries parameter in healthcheck control?

The retries parameter in the healthcheck section specifies the number of consecutive failures allowed before the container is deemed unhealthy.

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How does the host network setting in Docker Compose affect containers?

Specifying host under networks in Docker Compose enables containers to access the host's networking stack directly.

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Why are environment variables essential in containerized applications?

Defining environment variables in containerized applications is crucial for maintaining different settings across development and production environments.

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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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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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