305-300 Practice Exam 2 — 20 Questions

Question 1

What is the default behavior of Vagrant when a box is not found locally on the host machine?

Accepted Answer

It downloads it from the Vagrant Cloud. When Vagrant is asked to bring up a machine and the specified box is not present locally, it automatically attempts to download the box from the configured box repository, which by default is Vagrant Cloud (formerly Atlas). This behavior is controlled by the box_url or the shorthand box name in the Vagrantfile, and Vagrant will fetch the box metadata and then the box file itself. No user prompt is required unless the box is not found in the repository or there is an ambiguity.

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It prompts for a path

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It creates an empty machine

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It fails immediately

Question 2

You are using Docker and want to create a volume that is shared between multiple containers and persists even if the containers are deleted. What is the best approach?

Accepted Answer

Named volume. A named volume is created and managed by Docker with a user-specified name, stored under /var/lib/docker/volumes, and persists independently of container lifecycle. It can be mounted into multiple containers simultaneously, making it the best choice for shared, persistent data. Named volumes are the recommended approach for production data persistence.

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Anonymous volume

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Tmpfs

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Bind mount

Question 3

A VM is hanging because of a specific hardware emulation bug in QEMU. You need to enable the 'qxl' video device to see if it resolves display issues. What is the XML tag to define the video device in the domain config?

Accepted Answer

. In libvirt domain XML, video devices are defined with the

Answer

Answer

Answer

Question 4

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

Accepted Answer

COPY. The COPY instruction copies files or directories from the build context (host) into the image filesystem. It is the preferred instruction for straightforward file copying because it does not perform any automatic extraction or remote URL fetching. COPY is explicit and predictable.

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RUN

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ADD

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PUSH

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IMPORT

Question 5

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

Accepted Answer

jail. The jail utility is the standard FreeBSD command for creating, starting, and managing jails. Running jail with parameters such as path, hostname, and command starts a new jail. It is the foundational management tool, complemented by jexec for entering a running jail and jls for listing jails.

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jexec

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jails-admin

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jail-manage

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jls

Question 6

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 native QEMU/KVM disk image format designed to support copy-on-write, internal and external snapshots, zlib/zstd compression, and encryption. It grows dynamically as data is written and only allocates blocks on demand, making it ideal for VM images where space efficiency and snapshotting matter.

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vmdk

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vhdx

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raw

Question 7

You need to convert a raw disk image to QCOW2 format to enable snapshotting. Which command is correct?

Accepted Answer

qemu-img convert -f raw -O qcow2 source.img target.qcow2. The correct syntax is 'qemu-img convert -f raw -O qcow2 source.img target.qcow2'. The -f flag specifies the source format and -O (capital O) specifies the destination format. This is the canonical way to convert a raw image into QCOW2 so that snapshots, compression, and backing files become available.

Answer

qemu-img convert -i raw -o qcow2 source.img target.qcow2

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virsh image-convert source.img target.qcow2

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qemu-img change -f raw -t qcow2 source.img

Question 8

In the context of virtualization, what does 'ballooning' refer to?

Accepted Answer

Dynamically resizing guest memory. Ballooning is a memory reclamation technique where a special 'balloon' driver inside the guest OS inflates by allocating guest memory pages, forcing the guest to swap or release them back to the hypervisor for use by other VMs. When the hypervisor needs memory, it tells the balloon to inflate; when memory pressure subsides, the balloon deflates and returns pages to the guest. This allows dynamic resizing of guest memory without rebooting the VM.

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Scaling network bandwidth for a VM

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Increasing the number of virtual CPUs

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Compressing disk images on the fly

Question 9

Which command is used to display the XML configuration of a running VM domain named 'webserver'?

Accepted Answer

virsh dumpxml webserver. virsh dumpxml outputs the full XML definition of a domain, and when the domain is running it reflects the live configuration. This is the standard libvirt command for inspecting a VM's XML. The other options are not valid virsh subcommands for this purpose.

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virsh export webserver

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virsh show-config webserver

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virsh get-xml webserver

Question 10

What is the default location for libvirt domain configuration XML files?

Accepted Answer

/etc/libvirt/qemu/. The default location for libvirt domain configuration XML files is /etc/libvirt/qemu/. This directory holds the persistent XML definitions for QEMU/KVM domains, which are used by libvirt to manage and start virtual machines. When a domain is defined with virsh define, its XML is stored here.

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/var/lib/libvirt/domains/

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/etc/libvirt/networks/

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/usr/share/libvirt/

Question 11

Which hypervisor is known for being 'Type 2'?

Accepted Answer

VirtualBox. VirtualBox is classified as a Type 2 hypervisor because it runs as an application on top of a host operating system (Windows, Linux, macOS), relying on the host OS for scheduling, memory management, and I/O. It does not run directly on bare metal like Type 1 hypervisors. This hosted architecture is the defining characteristic of Type 2.

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KVM

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ESXi

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Xen

Question 12

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

Accepted Answer

-d. The `-d` (or `--detach`) flag tells `docker run` to start the container and immediately return control to the shell, running the container in the background. Without it, the container runs in the foreground and attaches its STDOUT/STDERR to your terminal, blocking the prompt until the process exits. This is the standard way to launch long-running services like web servers or databases.

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-t

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-b

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-i

Question 13

In cloud-init, which syntax is required at the very beginning of the configuration file to ensure it is recognized as a cloud-config script?

Accepted Answer

#cloud-config. Cloud-init identifies a cloud-config file by the literal header #cloud-config on the very first line. Without this exact shebang-style marker, cloud-init treats the payload as a different user-data format (e.g., shell script or MIME multipart) and will not process the YAML directives.

Answer

#!/bin/bash

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#cloud-init

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---

Question 14

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

Accepted Answer

-d. The -d (or --detach) flag runs a Docker container in the background, returning the container ID and freeing the terminal. This is the standard way to start long-running services like web servers without blocking the shell. Combined with -p for port mapping and --name for identification, it is the canonical detached-mode invocation.

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-i

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--bg

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-b

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-t

Question 15

Which TWO components are defined in a Packer 'build' block?

Accepted Answer

sources. In a Packer HCL2 template, the build block is where you declare the sources (option C) that Packer will use to create the image, referencing source blocks defined elsewhere in the template, and the provisioners (option E) that run during the build to customize the machine before the image is captured. Both sources and provisioners are valid arguments inside a build block, e.g. build { sources = ["source.amazon-ebs.example"] provisioners = [ ... ] }. Option A (builders) is not correct because in HCL2 templates the builder is defined inside a source block, not directly as a build block argument. Option B (plugins) is not a build block argument; plugins are installed via packer init and referenced through their source types. Option D (variables) is not defined inside the build block; variables are declared in variable blocks and referenced with var.<name>.

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builders

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plugins

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variables

Question 16

Which tool is commonly used alongside Packer to validate the configuration file for syntax errors before attempting a build?

Accepted Answer

packer validate. `packer validate` is the built-in Packer subcommand that parses a template (HCL2 or JSON) and verifies its syntax, required fields, and referenced variables/builders before any build is attempted. It catches schema errors, missing required attributes, and invalid references without provisioning any infrastructure. This makes it the standard pre-build sanity check in CI pipelines alongside `packer fmt`.

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packer fmt

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packer lint

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packer check

Question 17

Which utility is best for creating a new libvirt storage pool?

Accepted Answer

virsh pool-define-as. virsh pool-define-as creates a persistent storage pool definition in libvirt's configuration without starting it, which is the correct first step for creating a new pool. After defining, you run virsh pool-build (if needed) and virsh pool-start to activate it.

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virsh pool-create

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virt-pool-builder

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virsh add-pool

Question 18

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

Accepted Answer

overlay2. overlay2 (A) is a valid Docker storage driver that uses the OverlayFS union filesystem to stack image layers and is the default driver on most modern Linux distributions. aufs (E) is also a valid Docker storage driver, historically used on Ubuntu/Debian, that implements a union mount to manage image layers. ext4 (B) is a filesystem, not a Docker storage driver, so it cannot manage image layers. vfs-driver (C) is not a real driver name; the actual driver is 'vfs', and it is a simple non-union driver, but the option as written is incorrect. zfs-layer (D) is not a valid driver name; the actual Docker driver is 'zfs', so this option is incorrect.

Answer

ext4

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vfs-driver

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zfs-layer

Question 19

You are using QEMU to emulate an ARM architecture on an x86 host. Which binary would you typically use to execute this?

Accepted Answer

qemu-system-arm. qemu-system-arm is the QEMU binary that emulates a full ARM system, including CPU, memory, and peripherals, allowing you to run an ARM operating system on an x86 host. The 'system' prefix indicates full-system emulation, as opposed to user-mode emulation. This is the correct binary for booting an ARM kernel or OS image.

Answer

qemu-x86_64-arm

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qemu-arm

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qemu-system-x86_64

Question 20

Which command lists all Docker images currently on the host?

Accepted Answer

docker images. 'docker images' queries the local image store and lists all images present on the host, showing repository, tag, image ID, creation time, and size. It is the canonical command for inspecting locally cached images before running or removing them.

Answer

docker ps

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docker show

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docker list