305-300 Practice Test 3 — 25 Questions

Question 1

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 2

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 3

In systemd-nspawn, how do you specify a different root directory for the container?

Accepted Answer

-D. The -D or --directory flag specifies the root path.

Answer

--path

Answer

--root

Answer

-r

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

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 6

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 7

What is the main advantage of using a container over a virtual machine?

Accepted Answer

Lighter weight and faster startup. Containers share the host kernel, making them significantly lighter and faster to start than VMs.

Answer

Ability to run different kernels

Answer

Stronger security isolation

Answer

No network configuration

Question 8

Which THREE commands are used to manage the lifecycle of an LXC container?

Accepted Answer

lxc-start. lxc-start, lxc-stop, and lxc-destroy are standard commands for managing container states.

Answer

lxc-pause

Answer

lxc-reboot

Question 9

You are debugging a Docker image buildup that fails at the 'RUN' instruction due to missing network access during the build. What command option should be checked if the build environment uses a proxy?

Accepted Answer

--build-arg. Docker builds do not automatically inherit environment variables from the host's shell unless specified via --build-arg.

Answer

--proxy

Answer

--privileged

Answer

--network=host

Answer

--env-file

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

Which TWO of the following are true regarding the differences between rkt (Rocket) and Docker?

Accepted Answer

rkt utilized a daemonless architecture. rkt focused on pods and a daemonless architecture, whereas Docker initially used a centralized daemon.

Answer

rkt only supported binary images

Answer

Docker is a sub-project of rkt

Answer

Docker never had a daemon

Question 12

Which command is used to list all active running domains?

Accepted Answer

virsh list. virsh list lists active domains by default.

Answer

virsh domlist

Answer

virsh status

Answer

virsh list --all

Question 13

Which TWO of the following are valid ways to configure VM networking?

Accepted Answer

NAT. Bridging and NAT are both native libvirt network configuration methods.

Answer

Hub-based switching

Answer

VLAN tagging on bridge

Answer

Direct routing

Question 14

Which THREE configuration items can be managed by LXC cgroups?

Accepted Answer

CPU shares. Cgroups manage memory, CPU, and device access.

Answer

User permissions

Answer

DNS settings

Question 15

A Docker container running a web server is unable to serve traffic on port 8080. You verify the Dockerfile exposes port 80. What is the correct way to map this for external access?

Accepted Answer

docker run -p 8080:80. The -p flag in docker run is used to map host ports to container ports.

Answer

docker run -p 80:8080

Answer

docker run --net host

Answer

docker run --expose 8080

Answer

docker run -P 8080

Question 16

Which TWO pieces of information does Packer require to build an image for an existing cloud environment?

Accepted Answer

API credentials. Packer needs credentials (like API keys) and region/availability zone information to interact with cloud APIs.

Answer

Local disk path

Answer

BIOS password

Answer

Host OS version

Question 17

Which file system format is specifically designed for QEMU/KVM to support advanced features like copy-on-write, snapshots, and compression?

Accepted Answer

qcow2. QCOW2 (QEMU Copy-On-Write version 2) is the standard format for KVM that supports these features.

Answer

vmdk

Answer

vhdx

Answer

raw

Question 18

Which THREE of the following are required for a successful live migration between two KVM hosts using libvirt?

Accepted Answer

Shared storage. Shared storage, SSH access, and matching CPU models are critical requirements for a smooth live migration.

Answer

Identical network card models

Answer

Matching guest kernel versions

Question 19

You are migrating a legacy application to an LXC container and need to ensure the container has access to the host's /dev/sda block device. Which configuration key must be added to the container's configuration file?

Accepted Answer

lxc.cgroup.devices.allow = b 8:0 rwm. To allow a container to access host devices, the lxc.cgroup.devices.allow and lxc.mount.entry must be configured properly in the container config.

Answer

lxc.mount.device = /dev/sda

Answer

lxc.cap.sys_admin = 1

Answer

lxc.dev.access = /dev/sda

Question 20

Which TWO of the following are valid storage drivers used by Docker to manage image layers?

Accepted Answer

overlay2. Overlay2 and aufs are both well-known storage drivers for Docker.

Answer

ext4

Answer

vfs-driver

Answer

zfs-layer