305-300 Full Virtualization Practice Test 2 — 15 Questions

Question 1

Which THREE of the following are valid options for 'virsh shutdown'?

Accepted Answer

--mode acpi. The virsh shutdown command accepts a --mode option that selects how the guest is asked to power down: --mode acpi (A) sends an ACPI power-button event so the guest OS performs a clean, orderly shutdown; --mode agent (B) uses the QEMU guest agent (qemu-guest-agent) to request shutdown from inside the guest; and --mode initctl (C) triggers the shutdown via the guest's initctl/systemd mechanism. These three are the documented valid values for --mode in virsh shutdown. Options D (--mode force) and E (--mode hard) are not valid values for virsh shutdown; forced or hard power-off is performed with virsh destroy, not by a shutdown mode.

Answer

--mode force

Answer

--mode hard

Question 2

Which TWO of the following are valid ways to manage storage pools using virsh?

Accepted Answer

virsh pool-create-as. Option C, virsh pool-create-as, is correct because it both defines a new storage pool from the given command-line parameters (name, type, and source/target details) and immediately starts it in one step, making it a valid way to create and manage a pool. Option D, virsh pool-define-as, is correct because it defines a persistent storage pool from command-line arguments without starting it, which is a standard virsh method for managing pool definitions (later activated with virsh pool-start). The other options are not valid virsh subcommands: virsh pool-mount (A) does not exist, virsh pool-resize (B) is not a real subcommand (resizing is done via virsh pool-set or editing the XML and redefining), and virsh pool-format (E) is not a virsh command for managing storage pools.

Answer

virsh pool-mount

Answer

virsh pool-resize

Answer

virsh pool-format

Question 3

When migrating a domain with virsh, which TWO of the following options can be used to ensure the migration is successful if the destination host has a different CPU architecture or feature set?

Accepted Answer

--cpu-mode host-model. Option B (--cpu-mode host-model) is correct because it exposes a CPU model that mirrors the destination host's capabilities, allowing libvirt to present a compatible CPU definition so the guest can start on a host with a different feature set. Option E (--cpu-mode custom) is correct because it lets you supply an explicit, tailored CPU model/feature list (via the domain XML <cpu> element) that matches the destination host's architecture and features, ensuring the migrated domain boots successfully. Options A (--persistent) and C (--undefine-source) only control the persistence of the domain definition and cleanup of the source, not CPU compatibility, so they do not address differing architectures or feature sets. Option D (--live) merely requests a live migration and says nothing about reconciling CPU differences, so it does not ensure success across heterogeneous hosts.

Answer

--persistent

Answer

--undefine-source

Answer

--live

Question 4

A KVM host runs a Windows guest that performs many random writes. The host's storage backend is a local LVM volume group. You want to avoid host-side fragmentation and reduce write amplification by preallocating the entire guest disk image at creation time. Which command creates a raw image named win10.img of 80 GiB with full allocation?

Accepted Answer

dd if=/dev/zero of=win10.img bs=1M count=81920 conv=fsync. A raw image is fully allocated when every block is written to the underlying filesystem. The dd approach writes zeros across the entire 80 GiB, forcing allocation and eliminating sparse regions that can fragment over time. The qcow2 variant would satisfy preallocation but produces the wrong format, and the two malformed qemu-img invocations either use an unsupported option or an invalid syntax.

Answer

qemu-img create -f raw -o preallocation=full win10.img 80G

Answer

qemu-img create -f raw -o size=80G win10.img

Answer

qemu-img create -f qcow2 -o preallocation=full win10.img 80G

Question 5

You are preparing a KVM guest for a live migration with virsh migrate --live and want the guest's disk writes to be tracked on the source host so that only dirty blocks are transferred after the memory copy begins. The guest disk is a raw image on a local LVM logical volume, and the destination host can reach the source's storage via a shared Fibre Channel LUN, but the LUN is not yet visible on the destination. Which action must you take on the source host before starting the migration to enable dirty-block tracking for this disk?

Accepted Answer

Start a block copy job with virsh blockcopy --domain guest --path vda --dest /dev/mapper/vg_lun --wait --verbose to mirror writes to the shared LUN.. Live migration with only dirty blocks transferred requires a mechanism that records writes while the guest runs. A block copy job using virsh blockcopy mirrors the disk to the destination and maintains a dirty bitmap, so the final pass copies only changed blocks. The destination must be able to see the target LUN, which the shared Fibre Channel setup provides once the copy job points to it.

Answer

Edit the domain XML and add <driver name='qemu' type='raw' cache='none' io='native'/> to the disk definition, then redefine the domain.

Answer

Convert the raw LVM volume to a qcow2 file with qemu-img convert -O qcow2, then start the migration.

Answer

Run virsh domblkthreshold --domain guest --dev vda --threshold 0 to force libvirt to record writes.

Question 6

A KVM guest is configured with a virtio-blk disk backed by a qcow2 image on an NFS mount. During heavy write activity, the guest reports I/O errors and the host logs show 'nfs: server not responding'. You need to improve resilience so that transient NFS outages do not immediately cause guest I/O failures. Which QEMU block device cache mode should you set for the disk to allow the guest to continue operating during brief NFS stalls?

Accepted Answer

cache=writeback. With cache=writeback, the host page cache absorbs writes and acknowledges them to the guest before they reach the NFS server. This buffering allows the guest to keep running during short NFS outages, preventing immediate I/O errors. Other cache modes either force synchronous writes to the network storage or sacrifice data integrity without providing the intended resilience.

Answer

cache=none

Answer

cache=unsafe

Answer

cache=directsync

Question 7

An administrator needs to create a new libvirt storage pool that stores disk images in a directory on the host and make it available to libvirt, but the directory does not yet exist. Which sequence of virsh commands correctly defines, starts, and activates the pool persistently?

Accepted Answer

virsh pool-define-as images dir --target /srv/vmdisks; virsh pool-build images; virsh pool-start images; virsh pool-autostart images. A directory pool that must persist and whose target directory does not exist requires define, build, start, and autostart. pool-define-as records the persistent configuration, pool-build creates and prepares the target path, pool-start makes it active now, and pool-autostart ensures activation after reboot. Skipping build fails on the missing directory, and skipping autostart breaks persistence across restarts.

Answer

mkdir -p /srv/vmdisks; virsh pool-define-as images dir --target /srv/vmdisks; virsh pool-start images

Answer

virsh pool-define-as images dir --target /srv/vmdisks; virsh pool-start images

Answer

virsh pool-create-as default dir --target /var/lib/libvirt/images

Question 8

A KVM host uses a storage pool of type 'logical' backed by an LVM volume group named vg_vms. You need to create a new 20 GB volume for a guest directly from this pool using virsh. Which command accomplishes this?

Accepted Answer

virsh vol-create-as vmpool guest1 20G. Provisioning a volume inside an existing libvirt storage pool is done with vol-create-as, specifying the pool name, volume name, and capacity. This uses libvirt's storage driver to allocate the underlying LV in the logical pool. The other commands either create pools, list volumes, or misuse required arguments, and none of them allocate the requested 20 GB volume.

Answer

virsh vol-list vmpool --create guest1 20G

Answer

virsh vol-create-as vg_vms guest1.img 20G

Answer

virsh pool-create-as vmpool logical 20G

Question 9

A running KVM guest named db1 has its root disk on a qcow2 image. You need to create a point-in-time snapshot of the guest's disk and memory state so it can be reverted later, while keeping the guest running. Which virsh command should you use?

Accepted Answer

virsh snapshot-create-as db1 snap1. To capture both disk and memory state of a running guest for later reversion, snapshot-create-as without disk-only or external flags creates an internal snapshot containing the full state. Disk-only omits memory, memspec requires an external disk snapshot, and save stops the guest rather than snapshotting it.

Answer

virsh save db1 /var/lib/libvirt/save/db1.save

Answer

virsh snapshot-create-as db1 snap1 --memspec file=/var/lib/libvirt/save/db1.mem,snapshot=external

Answer

virsh snapshot-create-as db1 snap1 --disk-only

Question 10

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 11

Which command is used to list all defined virtual networks in Libvirt?

Accepted Answer

virsh net-list --all. The `virsh net-list --all` command queries libvirt's virtual network driver and displays every network defined in the hypervisor, including those that are currently inactive. The `--all` flag is essential because without it, virsh only shows networks that are actively running. This is the canonical libvirt-native way to enumerate virtual networks, as opposed to inspecting the underlying Linux bridge layer.

Answer

brctl show

Answer

virsh domiflist

Answer

virsh list-networks

Question 12

You are configuring a Xen guest that requires direct hardware access to a specific network interface card. Which configuration parameter in the guest domain configuration file must be specified to enable PCI passthrough?

Accepted Answer

pci = [ '00:1f.1' ]. In Xen guest configuration files, PCI passthrough is enabled by specifying the 'pci' parameter with a list of PCI addresses, e.g., pci = [ '00:1f.1' ]. This directly assigns the physical PCI device to the guest.

Answer

device_pass = 'eth0'

Answer

hw_access = '00:1f.1'

Answer

vif = [ 'type=pci, bus=00:1f.1' ]

Question 13

You are configuring a QEMU-KVM guest to use VirtIO-net. Which parameter in the QEMU command line correctly enables the virtio-net-pci device with a tap interface named tap0?

Accepted Answer

-netdev tap,id=net0,ifname=tap0 -device virtio-net-pci,netdev=net0. The correct QEMU command line uses '-netdev tap,id=net0,ifname=tap0' to define a tap network backend with a unique ID, and then '-device virtio-net-pci,netdev=net0' to attach a virtio-net-pci device to that backend. This two-part syntax is required in modern QEMU to separate the network backend from the device frontend.

Answer

-device virtio-net,backend=tap0

Answer

-netdev tap,id=tap0 -device virtio-net-pci,id=tap0

Answer

-net tap,ifname=tap0,model=virtio

Question 14

When managing storage pools using virsh, which command would you use to list all defined storage pools, including those that are inactive?

Accepted Answer

virsh pool-list --all. The correct command is `virsh pool-list --all`. In libvirt's virsh CLI, `pool-list` is the dedicated subcommand for enumerating storage pools, and the `--all` flag extends the default output (which shows only active pools) to include inactive pools as well. This mirrors the pattern used by `virsh list --all` for domains, making it the canonical way to see every defined pool regardless of state.

Answer

virsh list-pools --inactive

Answer

virsh pool-info --all

Answer

virsh pool-show --all

Question 15

Which hypervisor type is considered 'Type 1' virtualization?

Accepted Answer

Xen. Xen is a Type 1 (bare-metal) hypervisor because it runs directly on the host hardware, with the hypervisor itself acting as the lowest software layer and managing guest domains. Type 1 hypervisors do not require a host OS underneath them, giving better performance and isolation for production virtualization. Xen's dom0 and domU architecture is a textbook example of this model.

Answer

VMware Workstation

Answer

VirtualBox

Answer

QEMU (user mode)