305-300 Container Virtualization Practice Test 5 — 15 Questions

Question 1

When using systemd-nspawn, you want to limit the memory usage of a container to 512MB. Which flag should be passed to the systemd-nspawn command?

Accepted Answer

--memory-limit=512M. systemd-nspawn uses the --memory-limit flag to restrict the memory consumption of the spawned container.

Answer

--max-mem=512M

Answer

--cgroup-memory=512M

Answer

--limit-mem=512M

Question 2

When configuring a Docker volume that needs to be shared between multiple containers, which storage driver storage path is recommended to ensure persistent data availability if the host reboots?

Accepted Answer

-v /host/path:/container/path. Using a named volume or a bind mount to a host directory ensures persistence beyond the container lifecycle.

Answer

--link

Answer

--tmpfs

Answer

--volume-driver=none

Answer

--memory

Question 3

Which command-line tool is primarily used to inspect the metadata and configuration of a running Docker container?

Accepted Answer

docker inspect. docker inspect provides detailed information on containers and images in JSON format.

Answer

docker ps

Answer

docker stats

Answer

docker info

Answer

docker describe

Question 4

What is the primary function of the ENTRYPOINT instruction in a Dockerfile?

Accepted Answer

Configuring the executable that runs when the container starts. ENTRYPOINT sets the main command that will execute when the container starts.

Answer

Setting environment variables

Answer

Defining volume mount points

Answer

Specifying metadata

Answer

Installing software packages

Question 5

Which file is primarily responsible for defining the configuration and environment variables for an OpenVZ container?

Accepted Answer

/etc/vz/conf/CTID.conf. In OpenVZ, containers are managed via configuration files located in /etc/vz/conf/.

Answer

/etc/openvz/config

Answer

/var/lib/vz/config

Answer

/etc/vz/container.conf

Answer

/etc/vz/vz.conf

Question 6

You are using BSD Jails and need to start a jail. Which utility is the standard management tool for jail administration?

Accepted Answer

jail. jail is the command to create or start a jail, and jailctl is also sometimes used in managed environments, but jexec is used for executing commands inside.

Answer

jexec

Answer

jails-admin

Answer

jail-manage

Answer

jls

Question 7

You need to limit the amount of CPU shares a Docker container can utilize. Which flag should be used?

Accepted Answer

--cpu-shares. The --cpu-shares flag sets the relative CPU weight of a container.

Answer

--cpu-limit

Answer

--cpus

Answer

--max-cpu

Answer

--cpu-weight

Question 8

When cleaning up Docker resources, which command will remove all stopped containers, unused networks, and dangling images in one step?

Accepted Answer

docker system prune. docker system prune removes all unused data, which is the most efficient cleanup method.

Answer

docker container prune

Answer

docker volume prune

Answer

docker image prune -a

Answer

docker cleanup

Question 9

In the context of container orchestration, what is the role of a 'sidecar' container?

Accepted Answer

To provide auxiliary services like logging or monitoring for the main container. A sidecar container runs alongside the main application container within the same pod to extend or enhance its functionality.

Answer

To act as a load balancer for the cluster

Answer

To store persistent data for the primary container

Answer

To run in a separate network namespace

Answer

To replace the main container when it crashes

Question 10

Which kernel feature provides the isolation necessary for namespaces in container virtualization?

Accepted Answer

Namespaces. Namespaces are a Linux kernel feature that partition kernel resources, such as PID, network, and mount points.

Answer

OverlayFS

Answer

Seccomp

Answer

Cgroups

Answer

AppArmor

Question 11

You are debugging a Docker network issue where containers on different hosts cannot communicate. Which network driver is specifically designed to support multi-host overlay networking?

Accepted Answer

overlay. The 'overlay' driver in Docker creates a distributed network among multiple Docker daemon hosts.

Answer

bridge

Answer

macvlan

Answer

ipvlan

Answer

host

Question 12

What is the primary difference between a container image and a container instance?

Accepted Answer

The image is the template; the instance is the running process. A container image is a read-only template, whereas a container instance is a writable, running version of that image.

Answer

Images are stored in RAM, instances are on disk

Answer

Instances cannot be stopped

Answer

The instance is the template; the image is the running process

Answer

They are the same thing

Question 13

When configuring a systemd-nspawn container, what is the effect of the --private-network option?

Accepted Answer

It isolates the container's network from the host. The --private-network flag creates a virtual network namespace for the container, ensuring it cannot access the host's network interfaces.

Answer

It forces the container to use a bridge

Answer

It disables network encryption

Answer

It restricts access to localhost

Answer

It prevents the container from starting

Question 14

Which Dockerfile instruction is used to copy a file from the host file system into the image?

Accepted Answer

COPY. The COPY instruction is the standard way to move files from the build context into the image.

Answer

RUN

Answer

ADD

Answer

PUSH

Answer

IMPORT

Question 15

Which command-line option is used to run a Docker container in the background (detached mode)?

Accepted Answer

-d. The -d flag specifies that the container should run in the background.

Answer

-i

Answer

--bg

Answer

-b

Answer

-t