Docker Advanced Quiz

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Challenge yourself with advanced Docker concepts like Swarm, Internals, and Security.

Instructions:

• Select the best answer for each question.
• Your score will be shown at the end.

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What is Docker Swarm?

A native clustering and orchestration tool for Docker

A security scanning tool

A new file format

A database for Docker

Docker Swarm is the native clustering mode for Docker, allowing you to manage a cluster of Docker Engines as a single virtual system.

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Which feature allows you to optimize image size by copying artifacts from one stage to another?

Multi-stage builds

Docker Squash

Image Layering

Docker Compress

Multi-stage builds allow you to use intermediate images to build artifacts and copy only what's needed to the final image.

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Which namespace is responsible for process isolation in Docker?

PID namespace

NET namespace

MNT namespace

USER namespace

The Process ID (PID) namespace isolates the process ID number space, meaning processes in different PID namespaces can have the same PID.

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Which Cgroups features does Docker use?

Resource limiting (CPU, Memory)

Network isolation

Process isolation

Filesystem layers

Control Groups (cgroups) are used to limit, account for, and isolate the resource usage (CPU, memory, disk I/O, etc.) of a collection of processes.

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What is the command to initialize a Swarm?

docker swarm init

docker cluster create

docker init swarm

docker swarm start

docker swarm init initializes a swarm on the current node, making it a manager.

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In Docker Swarm, what is a "Service"?

The definition of the tasks to execute on the nodes

A running container

A network interface

A volume

A Service defines the image, commands, and configurations (replicas, ports) that the swarm manager uses to distribute Tasks to nodes.

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Which command removes all unused containers, networks, images, and build cache?

docker system prune

docker clean all

docker remove all

docker purge

docker system prune is a powerful command to clean up unused data. Adding -a removes specific unused images as well.

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What is the default isolation request for Windows Server containers?

process

hyperv

default

none

Windows Server containers default to process isolation. Hyper-V isolation can be requested for higher security.

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Which file is used to configure the Docker daemon?

daemon.json

docker.conf

config.json

dockerd.yaml

daemon.json (usually in /etc/docker/) is used to configure Daemon settings like logging drivers, insecure registries, etc.

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How can you ensure a container restarts automatically if it crashes?

--restart on-failure

--restart always-up

--keep-alive

--ensure-up

Using --restart on-failure (or always) in docker run ensures the container restarts based on the policy.

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Which feature allows you to sign images to ensure integrity?

Docker Content Trust (DCT)

Docker Secure

Docker Sign

Docker Verify

Docker Content Trust provides the ability to use digital signatures for data sent to and received from remote Docker registries.

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What is the ONBUILD instruction in a Dockerfile?

Adds a trigger instruction to the image to be executed at a later time, when the image is used as the base for another build

Runs immediately during build

Runs when container starts

Runs when image is pushed

ONBUILD instructions are executed when the image is used as a base for another image.

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How do you update a service in Docker Swarm without downtime?

docker service update

docker service upgrade

docker update service

docker swarm update

docker service update allows you to update the image, configuration, or scale of a service, often triggering a rolling update.

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Which command displays system-wide information?

docker info

docker sys

docker details

docker system

docker info displays system-wide information regarding the Docker installation.

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What is a "manifest list" (or multi-arch image)?

A list of images that correspond to different architectures (e.g., amd64, arm64) under a single tag

A list of all tags

A file containing image layers

A security manifest

Manifest lists allow a single tag (e.g., postgres:13) to support multiple architectures.

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How do you export a container's filesystem as a tar archive?

docker export

docker save

docker archive

docker tar

docker export exports a container’s filesystem. docker save saves an image.

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Which command saves one or more images to a tar archive?

docker save

docker export

docker backup

docker store

docker save saves the image (including all layers and history) to a tar file.

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How do you load an image from a tar archive (created by docker save)?

docker load

docker import

docker restore

docker open

docker load loads an image from a tar archive or STDIN.

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Which command creates a new image from a container's changes?

docker commit

docker save

docker image create

docker build

docker commit creates a new image from a container's changes.

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What is the purpose of STOPSIGNAL in Dockerfile?

Sets the system call signal that will be sent to the container to exit

Stops the build

Pauses the container

Defines the stop command

STOPSIGNAL sets the signal (e.g., SIGTERM, SIGKILL) used to stop the container.

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