305-300 Practice Test 2 — 30 Questions

Question 1

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 2

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 3

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 4

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 5

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 6

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 7

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 8

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 9

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 10

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 11

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 12

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

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Installing software packages

Question 13

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 14

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 15

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

Question 16

Which command is used to start a VM that has been defined?

Accepted Answer

virsh start vm_name. The correct command to start a defined but inactive libvirt domain (VM) is `virsh start vm_name`. This command initiates the domain from its persistent XML definition, transitioning it from the 'shut off' state to 'running'. It is the standard counterpart to `virsh shutdown` and `virsh destroy`.

Answer

virsh launch vm_name

Answer

virsh boot vm_name

Answer

virsh run vm_name

Question 17

You are configuring a virtual network in libvirt that allows VMs to communicate with each other and the host, but prevents them from accessing the external network. Which mode should you select for this network?

Accepted Answer

Isolated. An isolated libvirt network allows VMs to communicate with each other and with the host but provides no route to the external network, which is exactly the requirement. It uses a virtual bridge with no forwarding to a physical interface or NAT. The other modes all provide some form of external connectivity.

Answer

Bridge

Answer

Direct

Answer

NAT

Question 18

You are using QEMU to emulate an ARM architecture on an x86_64 host. You need to ensure the guest has access to the host's filesystem directly without configuring network shares. Which option is the correct way to pass a directory through to the guest?

Accepted Answer

-virtfs local,path=/data,mount_tag=host_data,security_model=passthrough. The -virtfs option with local,path=/data,mount_tag=host_data,security_model=passthrough configures a virtio-9p filesystem share that allows the guest to mount the host directory directly. This is the correct QEMU mechanism for passing a host directory to the guest without network shares.

Answer

-fsdev share,path=/data,id=host_data

Answer

-netdev user,hostfwd=dir:/data

Answer

-drive file=/data,format=raw,if=virtio

Question 19

Which THREE directives are valid under the cloud-init 'users' configuration section?

Accepted Answer

name. In the cloud-init 'users' configuration section, the 'name' directive (A) is valid and required, as it defines the login name of the user account to be created. The 'ssh_authorized_keys' directive (B) is also valid, allowing a list of public SSH keys to be injected into the user's ~/.ssh/authorized_keys file for passwordless authentication. The 'groups' directive (E) is valid as well, specifying a list of supplementary groups to which the user should be added. The 'expiration_date' option (C) is not a recognized cloud-init user directive; account expiration is handled via the 'expire' directive (or 'expiredate' in some schemas), not 'expiration_date'. The 'security_level' option (D) is not part of the cloud-init users schema at all and has no meaning in this context.

Answer

expiration_date

Answer

security_level

Question 20

What is the purpose of the virtio-balloon driver in a guest?

Accepted Answer

To enable memory ballooning. The virtio-balloon driver enables memory ballooning, a technique that allows the hypervisor to dynamically adjust the amount of memory allocated to a guest. The driver inflates or deflates a 'balloon' inside the guest, reclaiming or returning memory pages to the host. This helps optimize memory usage across VMs. It does not speed up network transfers, provide disk caching, or enable 3D graphics.

Answer

To speed up network transfers

Answer

To provide disk caching

Answer

To enable 3D graphics