305-300 Practice Test 2 — 25 Questions

Question 1

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

Question 2

Which hypervisor type is considered 'Type 1' virtualization?

Accepted Answer

Xen. Type 1 hypervisors (bare metal) run directly on the hardware, such as Xen.

Answer

VMware Workstation

Answer

VirtualBox

Answer

QEMU (user mode)

Question 3

You are optimizing a Dockerfile to reduce image size. Which THREE of the following practices are recommended?

Accepted Answer

Remove /var/lib/apt/lists/* after installing packages. Multi-stage builds, minimizing layers, and cleaning up caches are standard practices.

Answer

Use the FROM latest tag for all base images

Answer

Always install recommended packages for security

Question 4

In an OpenVZ environment, you need to limit the number of processes a container can create. Which parameter in the container configuration file should be modified?

Accepted Answer

NUMPROC. The 'nproc' (or numproc) parameter in the OpenVZ configuration limits the total number of processes a container is allowed to hold.

Answer

PHYSPAGES

Answer

KMEMSIZE

Answer

PRIVVMPAGES

Question 5

You are troubleshooting a problem where an LXC container cannot access its own /dev/null. What is a common cause in a non-root container?

Accepted Answer

Missing mknod permission. Lack of device node creation in the container's /dev directory or improper cgroup permissions often causes this.

Answer

Wrong kernel version

Answer

Host kernel panic

Answer

Insufficient RAM

Question 6

Which THREE storage drivers are supported by Docker?

Accepted Answer

devicemapper. Overlay2, devicemapper, and aufs are well-known Docker storage drivers.

Answer

xfs

Answer

ext4

Question 7

You are running a Docker container and need to map port 8080 on the host to port 80 in the container. Which command argument should you use?

Accepted Answer

-p 8080:80. The -p flag (or --publish) defines port mapping.

Answer

-p 80:8080

Answer

--port 8080:80

Answer

--map 8080:80

Question 8

When building a Dockerfile, which instruction should be used to define the user context for subsequent RUN, CMD, and ENTRYPOINT instructions?

Accepted Answer

USER. The USER instruction sets the UID/GID for processes executed in subsequent steps.

Answer

WORKDIR

Answer

RUN useradd

Answer

AS

Question 9

You are using systemd-nspawn. How do you create an image of a container to be used as a template?

Accepted Answer

machinectl export-tar. 'machinectl export-tar' is used to export a systemd-nspawn container (machine) to a tarball.

Answer

tar -cvf

Answer

docker export

Answer

lxc-copy

Question 10

Which TWO commands are valid for inspecting container network settings?

Accepted Answer

docker inspect. 'docker inspect' provides detailed JSON, and 'docker network inspect' shows network-specific details.

Answer

docker show net

Answer

docker net status

Answer

docker list network

Question 11

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 12

Which THREE instructions in a Dockerfile can modify the image's filesystem?

Accepted Answer

ADD. RUN, COPY, and ADD all add or modify content within the image layers.

Answer

ENV

Answer

EXPOSE

Question 13

When migrating a Libvirt domain using 'virsh migrate --live', which option must be specified to ensure the guest's memory state is copied over the network?

Accepted Answer

--copy-storage-all. The --live option manages the memory transfer, but the --copy-storage-all or --block-incremental option is required if the disks are not on shared storage.

Answer

--shared-storage

Answer

--migrate-disk

Answer

--memory-copy

Question 14

You need to inspect the metadata of a specific Docker image without pulling it from a remote registry. Which command should you use?

Accepted Answer

docker manifest inspect. docker manifest inspect allows retrieving information about an image's manifest without downloading the layers.

Answer

docker pull --metadata

Answer

docker image history

Answer

docker image inspect

Question 15

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 16

You are using an overlay network in Docker Swarm. What is the standard protocol used for the control plane and data plane communication between nodes?

Accepted Answer

VXLAN. VXLAN is the standard encapsulation protocol used by Docker overlay networks.

Answer

BGP

Answer

IPsec

Answer

GRE

Question 17

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 18

Which THREE items are typically included in an OpenVZ configuration file?

Accepted Answer

User Beancounters (resource limits). OpenVZ configs contain networking definitions, resource limits (UBC), and OS template references.

Answer

BIOS settings

Answer

Kernel source code

Question 19

You are configuring an OpenVZ container. Which command is used to set the hostname of the container from the host?

Accepted Answer

vzctl set CTID --hostname. 'vzctl set [CTID] --hostname [NAME] --save' is the correct command to update the container's hostname.

Answer

vzcfg

Answer

hostnamectl

Answer

openvz-edit

Question 20

Which TWO items are typically included in a Docker context?

Accepted Answer

Local files in the build directory. The Docker context includes the Dockerfile and the build directory contents.

Answer

The host kernel

Answer

Remote images

Answer

Running containers