Docker Interview Questions and Answer Part – 30

Images contain the entire user space, in other words the entire file system for a container. How is this not horribly inefficient in terms of disk space?

• Images are layered and common layers are shared (Ans)
• Images use state of the art compression to reduce the disk space requirements
• You only pull down the image layers that you need to run your application
• Image layers are highly optimized to reduce unnecessary components.

Say you have the following output from docker ps:
57cf9c689955 docs/docker.github.io “/bin/sh -c ‘jekyll s” About an hour ago Exited (137) About an hour ago grave_tesla

Which of the following does not work as a container identifier (CID) when running a command like the following?
docker stop
docker start
docker rm

• 57
• 57cf9c689955
• grave_tesla
• gra (Ans)

How do you terminate software running in a container?

• docker stop (Ans)
• docker rm
• docker terminate
• docker kill

Which of the following Windows Features do you need to use Windows Server containers?

• Docker
• Containers (Ans)
• Hyper-V and Containers
• Hyper-V

Which of the following stops all running containers?

• docker stop $(docker ps -q) (Ans)
• docker rmi $(docker ps -q)
• docker halt $(docker ps -q)
• docker rm -f $(docker ps -q)

Where do dangling volumes typically come from?

• Containers that we manually mount managed volumes into
• Images that have a VOLUME instruction (Ans)
• Containers that we bind-mount host volumes into
• Every container that is created has a volume created as well

Where are created, modified, and deleted files stored in a container?

• In a volume mounted in the container
• In an R/W container layer (Ans)
• In the bottom most layer from the image it was created from
• In the top most layer from the image it was created from

In the past, to launch an installed application, we would run an executable file. How does Docker run software?

• Pull a container
• Install a container
• Runs an executable (Ans)
• Create a container

How are image layers coalesced to form a container’s file system?

• Files are copied out of layers when creating a container into a union mount point
• A union file system is used to create a union mount point (Ans)
• Container file systems exist in memory, in a RAM disk, aggregated from image layers

How can you connect a container to a user defined network?

• –udf NETWORK_NAME
• docker connect
• –net NETWORK_NAME (Ans)
• docker attach
• docker disconnect

In traditional software management, we uninstall software to remove it from a machine, what’s the equivalent with Docker?

• Remove an image
• Uninstall a container
• Remove a container (Ans)
• Stop an image
• Stop a container

When you extract an image with docker save what is inside the tar archive?

• The contents of all layers flattened into one folder
• A folder for the entire image and also a layers folder with each layer nested inside
• A folder for each image layer (Ans)

The docker history command shows output similar to which of the following?

• Dockerfile (Ans)
• docker ps
• docker images
• docker-compose.yml
• docker layers

What is the role of Docker images?

• All of these
• Used to execute code at runtime
• Provides virtualization functionality across environments
• Acts as a blueprint or template that is used to create containers (Ans)

What command can be used to start a container?

• docker run [image name](Ans)
• docker go [image name]
• docker rm [image name]
• docker ps -a

Which of the following tasks can Docker Compose perform?

• View service logs
• None of these
• Build services
• All of these (Ans)
• Start and stop containers

Services can be organized into __ with Docker Cloud.

• groups
• stacks (Ans)
• roles
• zones

What Docker Compose command can be used to start multiple service containers?

• docker-compose up (Ans)
• docker-compose start
• None of these
• docker run

A Docker _ has a “thin R/W layer.”

• File
• Image
• None of these
• Container (Ans)

Each instruction in a Dockerfile creates an intermediate container as the image is built.

• True (Ans)
• False

What syntax can be used to convert a Dockerfile into an Image?

• docker create -t /tagName .
• docker run -t /tagName .
• docker run -t /tagName . (Ans)
• docker convert -t /tagName .

Which of the following tools are included in Docker Toolbox?

• All of these (Ans)
• Docker Machine
• Docker Client
• VirtualBox
• Docker Kitematic

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

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