305-300 Container Virtualization Practice Test 3 — 15 Questions

Question 1

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 2

Which Docker network driver should you use if you want containers to have their own IP addresses on the physical network, as if they were physically connected to the network?

Accepted Answer

macvlan. The 'macvlan' driver allows containers to be assigned a MAC address and IP on the physical network.

Answer

bridge

Answer

overlay

Answer

ipvlan

Question 3

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 4

When using 'docker-compose', which file format is used to define the services?

Accepted Answer

YAML. Docker Compose uses YAML files.

Answer

INI

Answer

XML

Answer

JSON

Question 5

How do you view the logs of a running container?

Accepted Answer

docker logs [container]. 'docker logs' is the command to retrieve logs.

Answer

docker show-logs

Answer

cat /var/lib/docker/logs

Answer

docker log

Question 6

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 7

In systemd-nspawn, how can you execute a command inside a container that is already running?

Accepted Answer

machinectl shell. 'machinectl shell' is the command used to spawn a shell inside a running container.

Answer

systemctl start

Answer

systemd-nspawn -run

Answer

nsenter

Question 8

Which command lists all Docker images currently on the host?

Accepted Answer

docker images. 'docker images' or 'docker image ls' lists images.

Answer

docker ps

Answer

docker show

Answer

docker list

Question 9

What is the purpose of the 'ENTRYPOINT' instruction in a Dockerfile?

Accepted Answer

To configure the container as an executable. ENTRYPOINT allows you to configure a container that will run as an executable.

Answer

To run build-time commands

Answer

To copy files

Answer

To set environment variables

Question 10

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 11

In a FreeBSD Jail, how can you ensure the jail starts automatically at boot?

Accepted Answer

Set jail_enable=YES in /etc/rc.conf. Setting 'jail_enable="YES"' in /etc/rc.conf is required for the jails subsystem to start.

Answer

Create a symlink in /etc/init.d

Answer

Use systemd

Answer

Add a cron job

Question 12

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 13

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

Question 14

Which THREE features are provided by Linux Namespaces in the context of containers?

Accepted Answer

PID isolation. Namespaces provide isolation for Process IDs, Networking, and Mount points.

Answer

CPU scheduling

Answer

Disk quotas

Question 15

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