305-300 Practice Test 17 — 15 Questions

Question 1

What does the term 'KVM' stand for?

Accepted Answer

Kernel-based Virtual Machine. KVM stands for Kernel-based Virtual Machine. It is a Linux kernel module that turns the Linux kernel into a Type-1 hypervisor by exposing hardware virtualization extensions (Intel VT-x, AMD-V) through /dev/kvm. QEMU typically runs on top of KVM to provide full machine emulation and device models.

Answer

K-Hypervisor Virtual Machine

Answer

Kernel Virtual Module

Answer

Kilo-Virtual Machine

Question 2

Which cloud-init module is responsible for setting the hostname of the instance during the initial boot process?

Accepted Answer

hostname. The cloud-init 'hostname' module is responsible for setting the instance's hostname and, optionally, the fully qualified domain name (FQDN) during initial boot. It reads the 'hostname' and 'fqdn' keys from the cloud-config or metadata service and applies them via the appropriate system tool. This module runs early in the cloud-init boot stages to ensure the instance is correctly identified before other services start.

Answer

system_name

Answer

network_config

Answer

set_hostname

Question 3

Which THREE configuration items can be managed by LXC cgroups?

Accepted Answer

CPU shares. LXC uses Linux control groups (cgroups) to isolate and limit container resource consumption, and CPU shares (A) are managed via the cpu cgroup subsystem (e.g., cpu.shares) to control relative CPU scheduling weight. Device access (C) is enforced through the devices cgroup subsystem, which uses an allow/deny list (devices.allow/devices.deny) to control which block and character devices a container may access. Memory limits (D) are handled by the memory cgroup subsystem (e.g., memory.limit_in_bytes) to cap RAM usage and trigger OOM behavior. User permissions (B) are not a cgroup function; they are governed by Linux user/group IDs, UID/GID mapping in the LXC config, and file permissions. DNS settings (E) are configured through files such as /etc/resolv.conf or LXC network configuration, not through cgroups.

Answer

User permissions

Answer

DNS settings

Question 4

You are optimizing a Dockerfile to reduce image size. Which THREE of the following practices are recommended?

Accepted Answer

Remove /var/lib/apt/lists/* after installing packages. Option C is correct because after running apt-get install, the package lists stored in /var/lib/apt/lists/* are no longer needed at runtime, and deleting them in the same RUN layer prevents them from being baked into the image and bloating its size. Option D is correct because multi-stage builds let you compile or build in an intermediate stage and copy only the resulting artifacts into a minimal final stage, so compilers, SDKs, and other build-time dependencies never end up in the shipped image. Option E is correct because chaining commands with && in a single RUN creates one layer; if you split them across multiple RUN instructions, intermediate files created and later deleted still persist in earlier layers and inflate the image. Option A is not recommended because the latest tag is mutable and non-deterministic, leading to unpredictable builds and larger or incompatible base images rather than a size optimization. Option B is not recommended because installing recommended packages pulls in extra dependencies you may not need, increasing image size and attack surface; --no-install-recommends is the preferred approach.

Answer

Use the FROM latest tag for all base images

Answer

Always install recommended packages for security

Question 5

Which file system structure is typically used for QEMU virtual disk images when using LVM?

Accepted Answer

/dev/vg_name/lv_name. When QEMU/KVM virtual disks are backed by LVM, the logical volume is exposed as a block device at /dev//, and that path is what QEMU uses as the disk source. LVM presents storage as block devices, not as file paths inside a filesystem.

Answer

/mnt/storage/disk.qcow2

Answer

/dev/sda1

Answer

/var/lib/libvirt/images/disk.img

Question 6

Which command is used to list all active running domains?

Accepted Answer

virsh list. The virsh list command lists all currently running domains (VMs) by default, showing their ID, name, and state. This is the standard libvirt CLI command for enumerating active guests. Adding --all extends the output to include inactive and shut-off domains, but the base command answers the question as asked.

Answer

virsh domlist

Answer

virsh status

Answer

virsh list --all

Question 7

You are troubleshooting a performance issue and want to pin a VM process to specific physical CPU cores. Which XML element is used?

Accepted Answer

. The element in libvirt domain XML is the dedicated container for CPU tuning parameters, and is the child element that binds a guest vCPU to a specific host CPU set. The vcpu attribute identifies the guest virtual CPU, while cpuset specifies the host physical CPUs (as a range or list) it may run on. This is the canonical, documented way to pin VM processes to physical cores in KVM/QEMU environments managed by libvirt.

Answer

Answer

<cpu-pinning vcpu='0' cpu='0'/>

Answer

Question 8

When using Packer with the QEMU builder, what does the 'format' option in the 'qemu' builder define?

Accepted Answer

The output image format. In the Packer QEMU builder, the 'format' option defines the output image format — for example 'qcow2', 'raw', 'vmdk', or 'vdi'. It tells QEMU how to write the resulting disk image so it is compatible with the target hypervisor or platform. This is distinct from filesystem or guest OS settings, which are configured elsewhere.

Answer

The filesystem type

Answer

The hypervisor type

Answer

The guest OS type

Question 9

Which THREE of the following are valid Libvirt storage pool types?

Accepted Answer

iscsi. Option B (iscsi) is correct because Libvirt supports an iSCSI storage pool type that connects to an iSCSI target and exposes its LUNs as volumes. Option C (lvm) is correct because Libvirt can use an existing LVM volume group as a storage pool, creating logical volumes as pool volumes. Option E (dir) is correct because the directory pool type is the most basic Libvirt pool, managing files in a local directory. Options A (ram) and D (usb) are not valid Libvirt storage pool types; Libvirt's defined pool types include dir, disk, fs, netfs, logical (LVM), iscsi, scsi, mpath, rbd, sheepdog, gluster, and zfs, but not ram or usb.

Answer

ram

Answer

usb

Question 10

You want to optimize disk I/O performance for a KVM guest. Which bus type should you configure in the libvirt domain XML for the virtual disk?

Accepted Answer

virtio. Virtio is a paravirtualized I/O driver framework designed specifically for KVM guests, providing near-native disk I/O performance by reducing the overhead of full hardware emulation. Configuring the disk bus as virtio in the libvirt domain XML (using <target dev='vda' bus='virtio'/>) allows the guest to use the virtio-blk or virtio-scsi driver, which significantly outperforms emulated IDE or SCSI controllers. This is the recommended bus type for production KVM workloads.

Answer

scsi

Answer

usb

Answer

ide

Question 11

You are debugging a Docker network issue where containers on different hosts cannot communicate. Which network driver is specifically designed to support multi-host overlay networking?

Accepted Answer

overlay. The 'overlay' driver is specifically designed for multi-host networking in Docker Swarm, using VXLAN tunnels to encapsulate container traffic across hosts. It creates a distributed network that spans multiple Docker daemons, enabling containers on different hosts to communicate as if on the same Layer 2 network.

Answer

bridge

Answer

macvlan

Answer

ipvlan

Answer

host

Question 12

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

Accepted Answer

API credentials. Packer needs API credentials (Option A) so its cloud builder can authenticate to the target cloud provider's API and create, register, and manage the resulting image on your behalf. Packer also needs the region (Option D) to know which geographic endpoint and datacenter location the image should be built in and stored, since cloud resources are region-scoped. A local disk path (Option B) is not required because Packer builds cloud images from a source image or template in the cloud, not from a local file path. A BIOS password (Option C) is irrelevant since Packer does not modify firmware settings during image builds. The host OS version (Option E) is not required because Packer runs on the build host but the target image's OS comes from the configured source image, not the host's OS version.

Answer

Local disk path

Answer

BIOS password

Answer

Host OS version

Question 13

You are migrating a running KVM guest from hostA to hostB with virsh migrate --live. The migration fails immediately with 'error: internal error: Attempt to migrate guest to the same host'. Both hosts share the same NFS storage and have identical CPU models. Which condition most likely explains this failure?

Accepted Answer

hostB resolves to the same IP address as hostA, or the migration URI points back to hostA.. libvirt compares the destination against the source host identity and aborts when they match, which is exactly what the 'same host' error indicates. The common causes are incorrect DNS or /etc/hosts entries, using a URI that resolves locally, or accidentally passing the local hostname as the destination. Confirming that hostB resolves to a distinct, reachable address and that the migration URI targets it resolves the issue.

Answer

The guest uses a virtio-net device without a configured migration address.

Answer

The guest's disk image is stored on local storage instead of the shared NFS mount.

Answer

The libvirt daemon on hostB is listening only on a Unix socket and not on TCP.

Question 14

A developer is building a container image and wants to reduce its final size by ensuring that no package manager cache files remain in the image layers. Which Dockerfile instruction should be used to remove these temporary files during the build?

Accepted Answer

RUN rm -rf /var/cache/apt/*. To reduce image size by removing temporary files, the deletion must occur in the same layer where the files were created. The RUN instruction executes commands during the build, so using RUN to remove cache files in the same layer ensures they are not committed to the final image. Other instructions like CMD, ENTRYPOINT, or ADD do not execute during build and cannot remove files.

Answer

ADD rm -rf /var/cache/apt/*

Answer

ENTRYPOINT rm -rf /var/cache/apt/*

Answer

CMD rm -rf /var/cache/apt/*

Question 15

You are building a Vagrant environment for a development team. The Vagrantfile must provision three identical web servers and one load balancer, all using the same base box but with different hostnames and static IP addresses. Which Vagrantfile construct should you use to define these machines and their individual settings?

Accepted Answer

config.vm.define. The config.vm.define method is used to declare multiple machines within a single Vagrantfile. Each definition block can set machine-specific attributes like hostname, network, and provider settings. This allows a single Vagrantfile to manage a multi-machine environment, which is exactly what is needed for three web servers and one load balancer.

Answer

config.vm.provider

Answer

config.vm.network

Answer

config.vm.provision