305-300 Practice Test 2 — 25 Questions

Question 1

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.

Answer

vmdk

Answer

vhdx

Answer

raw

Question 2

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

Answer

virsh image-convert source.img target.qcow2

Answer

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

Question 3

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.

Answer

Scaling network bandwidth for a VM

Answer

Increasing the number of virtual CPUs

Answer

Compressing disk images on the fly

Question 4

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.

Answer

virsh export webserver

Answer

virsh show-config webserver

Answer

virsh get-xml webserver

Question 5

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.

Answer

/var/lib/libvirt/domains/

Answer

/etc/libvirt/networks/

Answer

/usr/share/libvirt/

Question 6

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.

Answer

KVM

Answer

ESXi

Answer

Xen

Question 7

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.

Answer

-t

Answer

-b

Answer

-i

Question 8

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

Answer

#cloud-init

Answer

---

Question 9

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.

Answer

-i

Answer

--bg

Answer

-b

Answer

-t

Question 10

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>.

Answer

builders

Answer

plugins

Answer

variables

Question 11

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`.

Answer

packer fmt

Answer

packer lint

Answer

packer check

Question 12

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.

Answer

virsh pool-create

Answer

virt-pool-builder

Answer

virsh add-pool

Question 13

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

Answer

vfs-driver

Answer

zfs-layer

Question 14

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

Answer

qemu-arm

Answer

qemu-system-x86_64

Question 15

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

Answer

docker show

Answer

docker list

Question 16

Which TWO of the following commands are used for VM disk image management?

Accepted Answer

qemu-img create. Option B, `qemu-img create`, is correct because it is the standard qemu-img subcommand used to create a new VM disk image, specifying the format (e.g., qcow2, raw) and size. Option E, `qemu-img info`, is correct because it displays metadata about an existing disk image, such as its virtual size, disk size, format, and backing file. The other options are not valid qemu-img subcommands: `qemu-img list` (A) does not exist for enumerating images, `qemu-img status` (C) is not a qemu-img operation, and `qemu-img format` (D) is not a subcommand — formatting is done via the `-f`/`-O` options on create/convert.

Answer

qemu-img list

Answer

qemu-img status

Answer

qemu-img format

Question 17

What is the primary function of the cloud-init 'runcmd' module?

Accepted Answer

Running arbitrary shell commands. The cloud-init `runcmd` module executes arbitrary shell commands on the instance during the final stage of boot, after other configuration modules have run. It is commonly used to run scripts, start services, or perform custom setup that is not covered by declarative modules. Because it runs late in the boot sequence, it can rely on packages and files configured by earlier modules.

Answer

Setting the system locale

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Configuring users

Answer

Installing software packages

Question 18

You are troubleshooting a Docker container that cannot reach the internet despite the host having connectivity. The container uses the default bridge network. Which iptables chain is most likely causing the block?

Accepted Answer

FORWARD. Docker's default bridge network relies on the host's FORWARD chain to route packets between the docker0 bridge and the external interface. If the FORWARD chain's default policy is DROP (common on hardened hosts or when firewalld/ufw is misconfigured), container traffic is silently dropped even though the host itself has internet access. Docker normally inserts its own DOCKER-USER and DOCKER-FORWARD rules to permit this, but a conflicting firewall rule or a policy change can override them.

Answer

PREROUTING

Answer

POSTROUTING

Answer

OUTPUT

Question 19

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

Accepted Answer

To configure the container as an executable. ENTRYPOINT configures the container to run as an executable by defining the command that executes when the container starts. Arguments passed on 'docker run' are appended to ENTRYPOINT rather than replacing it, which is what makes the container behave like a standalone binary. This is distinct from CMD, which provides overridable defaults.

Answer

To run build-time commands

Answer

To copy files

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To set environment variables

Question 20

You need to attach a new block device to a running VM. What virsh command achieves this?

Accepted Answer

virsh attach-disk vm_name /path/to/img vda. The virsh attach-disk command is the standard way to hot-plug a new block device to a running domain. Its syntax is 'virsh attach-disk ' where source is the host image path and target is the guest device name (e.g., vda, vdb). This command modifies the domain's live XML and, with --persistent, also updates the saved configuration.

Answer

virsh attach-device-file vm_name /path/to/img

Answer

virsh add-device vm_name /path/to/img

Answer

virsh hotplug-disk vm_name /path/to/img