305-300 Container Virtualization Practice Test 2 — 15 Questions

Question 1

You are building a multi-stage Dockerfile and want to copy a binary from the 'builder' stage to the final stage. Which syntax is correct?

Accepted Answer

COPY --from=builder /bin/app /bin/app. 'COPY --from=stage_name source destination' is the syntax for multi-stage copying.

Answer

ADD --from=builder /bin/app /bin/app

Answer

COPY builder:/bin/app /bin/app

Answer

COPY --stage=builder /bin/app /bin/app

Question 2

When using Docker volumes, which type of mount should you use if you want the data to persist on the host filesystem at a specific, user-defined path?

Accepted Answer

Bind mount. Bind mounts allow mapping a specific host path to a container path, providing persistence at a known location.

Answer

Named volume

Answer

Anonymous volume

Answer

Tmpfs mount

Question 3

Which command is used to stop all running containers?

Accepted Answer

docker stop $(docker ps -q). 'docker stop $(docker ps -q)' pipes the IDs of running containers to the stop command.

Answer

docker kill --all

Answer

docker rm -f *

Answer

docker prune

Question 4

Which command allows you to enter an existing running container and execute a new command inside it?

Accepted Answer

docker exec. 'docker exec' is the standard command to run a new process in a running container.

Answer

docker commit

Answer

docker attach

Answer

docker run

Question 5

Which flag is used to run a container in the background?

Accepted Answer

-d. The -d or --detach flag runs the container in the background.

Answer

-t

Answer

-b

Answer

-i

Question 6

In a Docker environment, you are observing that container logs are consuming too much disk space. Which logging driver should you configure to limit the number and size of log files?

Accepted Answer

json-file. The 'json-file' logging driver supports 'max-size' and 'max-file' options to rotate and cap logs.

Answer

none

Answer

syslog

Answer

journald

Question 7

You are configuring LXC and want to set a CPU limit for a container. Which cgroup parameter is used to specify the quota of CPU time in microseconds?

Accepted Answer

lxc.cgroup.cpu.cfs_quota_us. lxc.cgroup.cpu.cfs_quota_us defines the number of microseconds the container can run in a period.

Answer

lxc.cgroup.cpu.limit

Answer

lxc.cgroup.cpu.shares

Answer

lxc.cgroup.cpu.period_us

Question 8

Which instruction in a Dockerfile is best suited for installing packages to minimize image size?

Accepted Answer

RUN apt-get update && apt-get install -y package && rm -rf /var/lib/apt/lists/*. Combining the update and install commands with 'rm -rf /var/lib/apt/lists/*' in a single RUN command prevents layer bloat.

Answer

COPY apt-cache /

Answer

CMD apt-get install package

Answer

RUN apt-get update && apt-get install -y package

Question 9

You are troubleshooting a container networking issue. You notice that traffic from the container is not being SNATed. What should you check in the iptables rules?

Accepted Answer

nat table, POSTROUTING chain. The POSTROUTING chain in the nat table is responsible for MASQUERADE rules used for SNAT.

Answer

nat table, PREROUTING chain

Answer

filter table, FORWARD chain

Answer

mangle table, OUTPUT chain

Question 10

What is the purpose of the 'rkt' (Rocket) container runtime?

Accepted Answer

To run pods in a secure, pluggable manner. rkt was designed as a pod-native container engine with a focus on security and composability.

Answer

To replace the kernel

Answer

To manage cloud infrastructure

Answer

To provide a GUI for Docker

Question 11

Which command is used to remove an unused Docker image?

Accepted Answer

docker rmi. 'docker rmi' is the command to remove an image.

Answer

docker rm

Answer

docker image delete

Answer

docker prune image

Question 12

You need to inspect the configuration of an LXC container named 'web'. Which command should you use?

Accepted Answer

lxc-info -n web. 'lxc-info -n web' displays information about the specified container.

Answer

lxc-check

Answer

lxc-ls

Answer

lxc-config

Question 13

In a Docker swarm, which mode of service publishing allows incoming traffic to be load-balanced across all healthy container replicas?

Accepted Answer

ingress. The 'ingress' network mode in Swarm allows external traffic to hit any node and be routed to a container via the routing mesh.

Answer

macvlan

Answer

overlay

Answer

host

Question 14

Which command shows the history of layers in a Docker image?

Accepted Answer

docker history. 'docker image history' displays the layers and the commands that created them.

Answer

docker log

Answer

docker layers

Answer

docker image info

Question 15

What is the primary function of a Docker Registry?

Accepted Answer

To store and distribute images. A registry stores and distributes Docker images.

Answer

To build images

Answer

To run containers

Answer

To manage networking