Docker And Containers Practice Exam

Question 1 Docker And Containers

What is Docker?

The HEALTHCHECK instruction defines a command to check container health, updating status in docker ps; Docker runs it periodically. Multi-stage builds use multiple FROM stages to optimize image size by copying only artifacts from a build stage to a runtime stage, discarding build tools. Docker is an open-source platform that automates the deployment, scaling, and management of applications inside containers using containerization technology. The ENTRYPOINT configures the container's executable, making CMD arguments to it; forms include exec or shell, overriding with docker run args.

Question 2 Docker And Containers

What is the WORKDIR instruction?

docker ps lists running containers; add -a to show all containers including stopped ones, with details like status and ports. The WORKDIR instruction sets the working directory for subsequent RUN, CMD, etc., creating it if nonexistent, e.g., WORKDIR /app. Docker volumes are persistent storage solutions that outlive container lifecycles, allowing data to be shared and accessed by multiple containers. docker service create --name <name> --replicas <num> <image> deploys a service; use docker service ls to list.

Question 3 Docker And Containers

What is container breakout?

Docker secrets are secure, encrypted objects storing sensitive data like passwords, accessible only to services via tmpfs mounts in Swarm mode. The RUN instruction executes commands in a new layer on top of the current image during build, e.g., RUN apt-get update for installing packages. Container breakout is a security vulnerability where a malicious container escapes isolation to access the host system, often via kernel exploits. docker-compose up builds/pulls images, creates networks/volumes, and starts services; add -d for detached mode.

Question 4 Docker And Containers

What does CMD in Dockerfile do?

The CMD instruction provides defaults for an executing container, specifying the command and arguments; only the last one is used if multiple. Set environment variable export DOCKER_CONTENT_TRUST=1; it requires signed images for docker pull and run. Docker Hub is a public registry service where users can store, share, and manage Docker images for easy access and distribution. Docker networking provides isolated network stacks for containers, enabling communication via bridge, host, overlay, or custom networks.

Question 5 Docker And Containers

What is the Docker daemon?

Use docker stop <container_id> to send a SIGTERM signal gracefully, or docker kill for immediate termination with SIGKILL. docker run creates and starts a container from a specified image, e.g., docker run -it ubuntu bash runs an interactive Ubuntu container. docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers. The Docker daemon (dockerd) is a persistent background process that manages Docker objects like images, containers, networks, and volumes via the Docker API.

Question 6 Docker And Containers

What is Docker Hub?

Docker Compose is a tool for defining and running multi-container Docker applications using a YAML file (docker-compose.yml) for services, networks, and volumes. Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability. Docker Hub is a public registry service where users can store, share, and manage Docker images for easy access and distribution. Docker is an open-source platform that automates the deployment, scaling, and management of applications inside containers using containerization technology.

Question 7 Docker And Containers

What is containerization?

Use docker build -t <name:tag> . in the directory containing the Dockerfile; the . specifies the build context as the current directory. The FROM instruction sets the base image for the Docker build, e.g., FROM ubuntu:20.04, which must be the first non-comment instruction. Containerization is a virtualization method that packages an application and its dependencies into a container, enabling consistent deployment across different environments without hypervisor overhead. Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability.

Question 8 Docker And Containers

What is the default Docker network?

Multi-stage builds use multiple FROM stages to optimize image size by copying only artifacts from a build stage to a runtime stage, discarding build tools. The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. A Dockerfile is a text file with instructions to build a Docker image automatically, defining the base image, dependencies, environment, and runtime commands. Use minimal base images like alpine, multi-stage builds, combine RUN layers with &&, clean package caches, and .dockerignore unnecessary files.

Question 9 Docker And Containers

What does the RUN instruction do in a Dockerfile?

The RUN instruction executes commands in a new layer on top of the current image during build, e.g., RUN apt-get update for installing packages. The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. A Dockerfile is a text file with instructions to build a Docker image automatically, defining the base image, dependencies, environment, and runtime commands. The WORKDIR instruction sets the working directory for subsequent RUN, CMD, etc., creating it if nonexistent, e.g., WORKDIR /app.

Question 10 Docker And Containers

What are best practices for Docker security?

Docker Compose is a tool for defining and running multi-container Docker applications using a YAML file (docker-compose.yml) for services, networks, and volumes. Docker secrets are secure, encrypted objects storing sensitive data like passwords, accessible only to services via tmpfs mounts in Swarm mode. Run as non-root user, use minimal images, scan for vulnerabilities (e.g., Trivy), enable content trust, limit capabilities, and avoid unnecessary privileges. Docker is an open-source platform that automates the deployment, scaling, and management of applications inside containers using containerization technology.

Question 11 Docker And Containers

What are Docker volumes?

Docker volumes are persistent storage solutions that outlive container lifecycles, allowing data to be shared and accessed by multiple containers. Docker Content Trust (DCT) ensures image integrity and publisher authenticity using Docker Notary for signing and verifying images during push/pull. Check logs with docker logs <container>, inspect with docker inspect, exec inside, verify resources, and review events with docker events. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host.

Question 12 Docker And Containers

What command starts services defined in docker-compose.yml?

Docker Hub is a public registry service where users can store, share, and manage Docker images for easy access and distribution. Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability. docker-compose up builds/pulls images, creates networks/volumes, and starts services; add -d for detached mode. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host.

Question 13 Docker And Containers

How do you enable Docker Content Trust?

Set environment variable export DOCKER_CONTENT_TRUST=1; it requires signed images for docker pull and run. Run as non-root user, use minimal images, scan for vulnerabilities (e.g., Trivy), enable content trust, limit capabilities, and avoid unnecessary privileges. Docker volumes are persistent storage solutions that outlive container lifecycles, allowing data to be shared and accessed by multiple containers. Docker networking provides isolated network stacks for containers, enabling communication via bridge, host, overlay, or custom networks.

Question 14 Docker And Containers

What is the difference between bind mounts and volumes?

Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability. The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. Use docker stop <container_id> to send a SIGTERM signal gracefully, or docker kill for immediate termination with SIGKILL. The .dockerignore file specifies patterns to exclude files from the build context, like node_modules, reducing build time and image size.

Question 15 Docker And Containers

What is the difference between a container and a virtual machine?

Containerization is a virtualization method that packages an application and its dependencies into a container, enabling consistent deployment across different environments without hypervisor overhead. docker swarm init initializes the current node as a manager; it outputs a join token for worker nodes. Containers share the host OS kernel and are lightweight, starting in seconds, while virtual machines include a full guest OS, making them heavier and slower to boot.
Containers virtualize at the OS level; VMs at the hardware level. Container breakout is a security vulnerability where a malicious container escapes isolation to access the host system, often via kernel exploits.

Question 16 Docker And Containers

How do you create a Docker volume?

docker ps lists running containers; add -a to show all containers including stopped ones, with details like status and ports. Docker Swarm is Docker's native clustering and orchestration tool for managing a swarm of Docker nodes, deploying services with replicas and load balancing. Docker networking provides isolated network stacks for containers, enabling communication via bridge, host, overlay, or custom networks. docker volume create <volume_name> creates a named volume; use docker volume ls to list them.

Question 17 Docker And Containers

How do you stop a running Docker container?

docker volume create <volume_name> creates a named volume; use docker volume ls to list them. Use docker stop <container_id> to send a SIGTERM signal gracefully, or docker kill for immediate termination with SIGKILL. The -d flag runs the container in detached mode in the background, printing the container ID, instead of foreground. docker service create --name <name> --replicas <num> <image> deploys a service; use docker service ls to list.

Question 18 Docker And Containers

What is a Docker container?

docker pull <image> downloads a Docker image from a registry like Docker Hub to your local machine for use in creating containers. Set environment variable export DOCKER_CONTENT_TRUST=1; it requires signed images for docker pull and run. A Docker container is a runnable instance of a Docker image, providing an isolated environment for running applications. The HEALTHCHECK instruction defines a command to check container health, updating status in docker ps; Docker runs it periodically.

Question 19 Docker And Containers

What does `docker pull` do?

The ENTRYPOINT configures the container's executable, making CMD arguments to it; forms include exec or shell, overriding with docker run args. docker volume create <volume_name> creates a named volume; use docker volume ls to list them. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host. docker pull <image> downloads a Docker image from a registry like Docker Hub to your local machine for use in creating containers.

Question 20 Docker And Containers

What is Docker layer caching?

Docker layer caching speeds up builds by reusing unchanged layers from previous images; changes invalidate cache from that layer onward. The HEALTHCHECK instruction defines a command to check container health, updating status in docker ps; Docker runs it periodically. The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root. docker exec -it <container_id> /bin/bash executes a command inside a running container, useful for interactive shell access.

Question 21 Docker And Containers

What is `docker exec`?

docker exec -it <container_id> /bin/bash executes a command inside a running container, useful for interactive shell access. On Ubuntu, add Docker's official GPG key, set up the repository, update package index, and install via sudo apt install docker-ce, then start and enable the service. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host. docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers.

Question 22 Docker And Containers

What are Docker secrets?

Use docker build -t <name:tag> . in the directory containing the Dockerfile; the . specifies the build context as the current directory. Run as non-root user, use minimal images, scan for vulnerabilities (e.g., Trivy), enable content trust, limit capabilities, and avoid unnecessary privileges. A Docker image is a read-only template containing the application code, libraries, dependencies, and configurations needed to create a container. Docker secrets are secure, encrypted objects storing sensitive data like passwords, accessible only to services via tmpfs mounts in Swarm mode.

Question 23 Docker And Containers

What is .dockerignore?

Docker layer caching speeds up builds by reusing unchanged layers from previous images; changes invalidate cache from that layer onward. Check logs with docker logs <container>, inspect with docker inspect, exec inside, verify resources, and review events with docker events. The .dockerignore file specifies patterns to exclude files from the build context, like node_modules, reducing build time and image size. Use docker build -t <name:tag> . in the directory containing the Dockerfile; the . specifies the build context as the current directory.

Question 24 Docker And Containers

What is a Docker image?

The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. A Docker image is a read-only template containing the application code, libraries, dependencies, and configurations needed to create a container. Overlay networks enable multi-host container communication in Docker Swarm, using VXLAN encapsulation for secure overlay across hosts. docker ps lists running containers; add -a to show all containers including stopped ones, with details like status and ports.

Question 25 Docker And Containers

How do you remove a stopped container?

A Docker service is a declarative definition of desired container state in Swarm mode, specifying image, replicas, networks, and resources for scaling. docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers. The ENTRYPOINT configures the container's executable, making CMD arguments to it; forms include exec or shell, overriding with docker run args. Use docker build -t <name:tag> . in the directory containing the Dockerfile; the . specifies the build context as the current directory.

Question 26 Docker And Containers

What is the FROM instruction in a Dockerfile?

A Docker image is a read-only template containing the application code, libraries, dependencies, and configurations needed to create a container. docker-compose logs <service_name> displays logs from specified services; omit name for all services. The FROM instruction sets the base image for the Docker build, e.g., FROM ubuntu:20.04, which must be the first non-comment instruction. On Ubuntu, add Docker's official GPG key, set up the repository, update package index, and install via sudo apt install docker-ce, then start and enable the service.

Question 27 Docker And Containers

What command deploys a service in Swarm?

Use minimal base images like alpine, multi-stage builds, combine RUN layers with &&, clean package caches, and .dockerignore unnecessary files. The CMD instruction provides defaults for an executing container, specifying the command and arguments; only the last one is used if multiple. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host. docker service create --name <name> --replicas <num> <image> deploys a service; use docker service ls to list.

Question 28 Docker And Containers

What is a container in computing?

The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root. Use docker stop <container_id> to send a SIGTERM signal gracefully, or docker kill for immediate termination with SIGKILL. A container is a lightweight, standalone, executable package that includes everything needed to run a piece of software, such as code, runtime, libraries, and dependencies, isolated from the host system. Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability.

Question 29 Docker And Containers

What is a Docker service?

A Docker service is a declarative definition of desired container state in Swarm mode, specifying image, replicas, networks, and resources for scaling. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host. Use minimal base images like alpine, multi-stage builds, combine RUN layers with &&, clean package caches, and .dockerignore unnecessary files. Run as non-root user, use minimal images, scan for vulnerabilities (e.g., Trivy), enable content trust, limit capabilities, and avoid unnecessary privileges.

Question 30 Docker And Containers

What is a Dockerfile?

A Dockerfile is a text file with instructions to build a Docker image automatically, defining the base image, dependencies, environment, and runtime commands. Set environment variable export DOCKER_CONTENT_TRUST=1; it requires signed images for docker pull and run. A Docker image is a read-only template containing the application code, libraries, dependencies, and configurations needed to create a container. docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers.

Question 31 Docker And Containers

What is Docker Swarm?

docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers. Docker Swarm is Docker's native clustering and orchestration tool for managing a swarm of Docker nodes, deploying services with replicas and load balancing. Docker Content Trust (DCT) ensures image integrity and publisher authenticity using Docker Notary for signing and verifying images during push/pull. docker run creates and starts a container from a specified image, e.g., docker run -it ubuntu bash runs an interactive Ubuntu container.

Question 32 Docker And Containers

How do you build a Docker image from a Dockerfile?

Use docker build -t <name:tag> . in the directory containing the Dockerfile; the . specifies the build context as the current directory. Check logs with docker logs <container>, inspect with docker inspect, exec inside, verify resources, and review events with docker events. docker-compose up builds/pulls images, creates networks/volumes, and starts services; add -d for detached mode. docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers.

Question 33 Docker And Containers

How do you view logs in Docker Compose?

Containers share the host OS kernel and are lightweight, starting in seconds, while virtual machines include a full guest OS, making them heavier and slower to boot.
Containers virtualize at the OS level; VMs at the hardware level. A Docker container is a runnable instance of a Docker image, providing an isolated environment for running applications. A Docker image is a read-only template containing the application code, libraries, dependencies, and configurations needed to create a container. docker-compose logs <service_name> displays logs from specified services; omit name for all services.

Question 34 Docker And Containers

What command lists all Docker images?

A Docker container is a runnable instance of a Docker image, providing an isolated environment for running applications. docker exec -it <container_id> /bin/bash executes a command inside a running container, useful for interactive shell access. docker images or docker image ls displays a list of locally available Docker images with details like repository, tag, ID, and size. Overlay networks enable multi-host container communication in Docker Swarm, using VXLAN encapsulation for secure overlay across hosts.

Question 35 Docker And Containers

What is a multi-stage build in Dockerfile?

Multi-stage builds use multiple FROM stages to optimize image size by copying only artifacts from a build stage to a runtime stage, discarding build tools. docker rm <container_id> removes one or more containers; use docker container prune to remove all stopped containers. Overlay networks enable multi-host container communication in Docker Swarm, using VXLAN encapsulation for secure overlay across hosts. Docker is an open-source platform that automates the deployment, scaling, and management of applications inside containers using containerization technology.

Question 36 Docker And Containers

What is USER instruction in Dockerfile?

The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root. The ENTRYPOINT configures the container's executable, making CMD arguments to it; forms include exec or shell, overriding with docker run args. Docker Hub is a public registry service where users can store, share, and manage Docker images for easy access and distribution. Run as non-root user, use minimal images, scan for vulnerabilities (e.g., Trivy), enable content trust, limit capabilities, and avoid unnecessary privileges.

Question 37 Docker And Containers

What command inspects a Docker object?

docker inspect <object> returns low-level JSON info about containers, images, volumes, etc., for debugging. docker exec -it <container_id> /bin/bash executes a command inside a running container, useful for interactive shell access. Docker secrets are secure, encrypted objects storing sensitive data like passwords, accessible only to services via tmpfs mounts in Swarm mode. docker-compose up builds/pulls images, creates networks/volumes, and starts services; add -d for detached mode.

Question 38 Docker And Containers

What are Docker overlays?

docker exec -it <container_id> /bin/bash executes a command inside a running container, useful for interactive shell access. Overlay networks enable multi-host container communication in Docker Swarm, using VXLAN encapsulation for secure overlay across hosts. docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host. docker service create --name <name> --replicas <num> <image> deploys a service; use docker service ls to list.

Question 39 Docker And Containers

What is Docker networking?

docker run creates and starts a container from a specified image, e.g., docker run -it ubuntu bash runs an interactive Ubuntu container. On Ubuntu, add Docker's official GPG key, set up the repository, update package index, and install via sudo apt install docker-ce, then start and enable the service. The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. Docker networking provides isolated network stacks for containers, enabling communication via bridge, host, overlay, or custom networks.

Question 40 Docker And Containers

How do you initialize a Docker Swarm?

The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root. Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability. Docker secrets are secure, encrypted objects storing sensitive data like passwords, accessible only to services via tmpfs mounts in Swarm mode. docker swarm init initializes the current node as a manager; it outputs a join token for worker nodes.

Question 41 Docker And Containers

What does the -d flag do with `docker run`?

docker inspect <object> returns low-level JSON info about containers, images, volumes, etc., for debugging. The -d flag runs the container in detached mode in the background, printing the container ID, instead of foreground. A Docker container is a runnable instance of a Docker image, providing an isolated environment for running applications. docker run creates and starts a container from a specified image, e.g., docker run -it ubuntu bash runs an interactive Ubuntu container.

Question 42 Docker And Containers

How do you install Docker on a Linux system?

A Docker image is a read-only template containing the application code, libraries, dependencies, and configurations needed to create a container. docker service create --name <name> --replicas <num> <image> deploys a service; use docker service ls to list. On Ubuntu, add Docker's official GPG key, set up the repository, update package index, and install via sudo apt install docker-ce, then start and enable the service. The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root.

Question 43 Docker And Containers

What is ENTRYPOINT in Dockerfile?

A Docker service is a declarative definition of desired container state in Swarm mode, specifying image, replicas, networks, and resources for scaling. Use minimal base images like alpine, multi-stage builds, combine RUN layers with &&, clean package caches, and .dockerignore unnecessary files. The ENTRYPOINT configures the container's executable, making CMD arguments to it; forms include exec or shell, overriding with docker run args. The WORKDIR instruction sets the working directory for subsequent RUN, CMD, etc., creating it if nonexistent, e.g., WORKDIR /app.

Question 44 Docker And Containers

What is HEALTHCHECK in Dockerfile?

A Docker service is a declarative definition of desired container state in Swarm mode, specifying image, replicas, networks, and resources for scaling. The HEALTHCHECK instruction defines a command to check container health, updating status in docker ps; Docker runs it periodically. The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. Bind mounts link a host directory to a container path directly, while named volumes are managed by Docker and stored in a specific host location for better portability.

Question 45 Docker And Containers

How do you troubleshoot a failing Docker container?

Set environment variable export DOCKER_CONTENT_TRUST=1; it requires signed images for docker pull and run. docker-compose up builds/pulls images, creates networks/volumes, and starts services; add -d for detached mode. Containers share the host OS kernel and are lightweight, starting in seconds, while virtual machines include a full guest OS, making them heavier and slower to boot.
Containers virtualize at the OS level; VMs at the hardware level. Check logs with docker logs <container>, inspect with docker inspect, exec inside, verify resources, and review events with docker events.

Question 46 Docker And Containers

How do you create a custom Docker network?

docker network create <network_name> creates a bridge network by default; specify --driver overlay for multi-host. Check logs with docker logs <container>, inspect with docker inspect, exec inside, verify resources, and review events with docker events. A container is a lightweight, standalone, executable package that includes everything needed to run a piece of software, such as code, runtime, libraries, and dependencies, isolated from the host system. The HEALTHCHECK instruction defines a command to check container health, updating status in docker ps; Docker runs it periodically.

Question 47 Docker And Containers

What is Docker Compose?

On Ubuntu, add Docker's official GPG key, set up the repository, update package index, and install via sudo apt install docker-ce, then start and enable the service. Docker Compose is a tool for defining and running multi-container Docker applications using a YAML file (docker-compose.yml) for services, networks, and volumes. docker-compose logs <service_name> displays logs from specified services; omit name for all services. The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root.

Question 48 Docker And Containers

What is Docker content trust?

The default 'bridge' network allows containers on the same host to communicate using IP addresses or custom names. docker swarm init initializes the current node as a manager; it outputs a join token for worker nodes. Docker Content Trust (DCT) ensures image integrity and publisher authenticity using Docker Notary for signing and verifying images during push/pull. The RUN instruction executes commands in a new layer on top of the current image during build, e.g., RUN apt-get update for installing packages.

Question 49 Docker And Containers

What is `docker ps`?

The USER instruction sets the user/group for RUN, CMD, and ENTRYPOINT, enhancing security by avoiding root. Use minimal base images like alpine, multi-stage builds, combine RUN layers with &&, clean package caches, and .dockerignore unnecessary files. The -d flag runs the container in detached mode in the background, printing the container ID, instead of foreground. docker ps lists running containers; add -a to show all containers including stopped ones, with details like status and ports.

Question 50 Docker And Containers

What is `docker run`?

The FROM instruction sets the base image for the Docker build, e.g., FROM ubuntu:20.04, which must be the first non-comment instruction. Use minimal base images like alpine, multi-stage builds, combine RUN layers with &&, clean package caches, and .dockerignore unnecessary files. docker run creates and starts a container from a specified image, e.g., docker run -it ubuntu bash runs an interactive Ubuntu container. docker inspect <object> returns low-level JSON info about containers, images, volumes, etc., for debugging.