305-300 Full Virtualization Practice Test 6 — 15 Questions

Question 1

Which TWO of the following are benefits of using the QCOW2 image format?

Accepted Answer

Dynamic allocation (sparse files). Option C is correct because QCOW2 (QEMU Copy-On-Write version 2) is a sparse image format: it allocates disk blocks only as guest data is actually written, so a 100 GB virtual disk consumes only as much host space as the data stored in it, and it can grow dynamically up to the configured virtual size. Option E is correct because QCOW2 natively supports internal snapshots (stored inside the image file) and external snapshots, allowing point-in-time states of a VM disk to be created and reverted without copying the whole image. Option A is wrong because multi-host file locking is a feature of clustered/shared storage filesystems such as GFS2 or OCFS2, not of the QCOW2 format itself; QCOW2 images are not designed for concurrent write access from multiple hosts. Option B is wrong because hardware acceleration (for example KVM, Intel VT-x/AMD-V, or virtio) is provided by the hypervisor and CPU, not by the image file format. Option D is wrong because QCOW2 does not provide native encryption for all filesystems; encryption in QEMU/KVM is typically handled via LUKS or the qcow2 encryption extension (AES-CBC with a single key), which is not a general 'all filesystems' encryption feature.

Answer

Multi-host file locking

Answer

Hardware acceleration

Answer

Native encryption for all filesystems

Question 2

Which THREE of the following are legitimate security concerns when managing a virtualization host?

Accepted Answer

Unencrypted VNC connections. Option A is correct because VNC is often used to remotely access a virtualization host's console or guest consoles, and VNC traffic is unencrypted by default, allowing credentials and session data to be intercepted on the network. Option B is correct because the libvirt socket (typically /var/run/libvirt/libvirt-sock) provides privileged management access to virtual machines; if permissions are misconfigured, unauthorized users could start, stop, or reconfigure guests. Option D is correct because guest-to-host breakout exploits target hypervisor or emulation vulnerabilities to escape the VM boundary and gain code execution on the host, which is a fundamental virtualization security risk. Option C is not a security concern but a performance/availability consideration, and option E is a storage performance issue rather than a security threat.

Answer

Network interface speed

Answer

Hard drive fragmentation

Question 3

Which THREE of the following attributes can be defined within the <memoryBacking> XML block?

Accepted Answer

. In libvirt domain XML, the element controls how a guest's memory is backed, and it accepts the , , and sub-elements. Option A, , is correct because it instructs libvirt to back the guest RAM with huge pages (e.g., via the hugepages mount) instead of regular 4 KiB pages. Option B, , is correct because it specifies a file-backed memory source (used with shared memory such as a memory-backend-file), which is valid inside . Option E, , is correct because it sets the VFIO/MLOCK-style locking of guest memory in RAM, preventing it from being swapped out. Options C () and D () are not valid children; swap limits and ballooning rates are configured through other mechanisms (e.g., memtune or the device), so they do not belong here.

Answer

<swap-limit/>

Answer

<balloon-rate/>

Question 4

Which TWO of the following are key features of the QEMU-KVM hypervisor?

Accepted Answer

Hardware-assisted virtualization. QEMU-KVM is a combination of the KVM kernel module and the QEMU userspace emulator, and its defining feature is hardware-assisted virtualization: KVM leverages CPU virtualization extensions such as Intel VT-x (vmx) and AMD-V (svm) to run guest code directly on the host CPU, which is why option A is correct. Option B is also correct because QEMU provides comprehensive device emulation, presenting virtual hardware such as IDE/SCSI controllers, NICs (e.g., e1000, virtio-net), VGA adapters, and USB controllers to guests, and it also supports paravirtualized virtio devices for performance. The remaining options do not belong: automated host patching (C) is a configuration-management function handled by tools like Ansible, Puppet, or yum/dnf, not by the hypervisor itself; an integrated disk backup service (D) is not part of QEMU-KVM, since backups are performed with external tools such as qemu-img, libvirt snapshots, or third-party backup software; and a built-in web server (E) is not a QEMU-KVM feature, as remote management is typically provided by separate stacks like libvirt, virt-manager, or oVirt/Proxmox.

Answer

Automated host patching

Answer

Integrated disk backup service

Answer

Built-in web server

Question 5

Which THREE of the following are necessary to enable QEMU guest agent integration?

Accepted Answer

Installing qemu-guest-agent inside the guest. Option A is correct because the QEMU guest agent requires the qemu-guest-agent package (or equivalent, e.g., qemu-ga) to be installed and running inside the guest OS so it can communicate over the virtio-serial channel. Option B is correct because the VM's libvirt XML must define a channel device of type 'unix' with the target name 'org.qemu.guest_agent.0' (typically using a virtio-serial port) to provide the host-guest communication path. Option D is correct because the channel device is only instantiated at VM start, so the guest must be restarted (or the domain rebooted) for the new channel to become available and the agent to connect. Option C is not required because the guest agent uses a virtio-serial channel, not a network bridge, so no bridge configuration is needed. Option E is not required because VNC password authentication is unrelated to guest agent integration and only affects graphical console access.

Answer

Adding a network bridge

Answer

Enabling VNC password

Question 6

Which TWO of the following are valid libvirt storage pool lifecycle commands?

Accepted Answer

pool-start. Option B, pool-start, is correct because it is a genuine virsh subcommand that activates a previously defined but inactive storage pool, making its backing storage available for allocation to guests. Option D, pool-destroy, is correct because it is the valid virsh command that stops an active storage pool, tearing down its runtime state without deleting its persistent definition. The other options are not libvirt commands: pool-halt (A) and pool-reboot (C) are not virsh storage pool subcommands at all, and pool-pause (E) does not exist, since libvirt storage pools have no pause state — only active/inactive and defined/undefined states managed via pool-start, pool-destroy, pool-define, and pool-undefine.

Answer

pool-halt

Answer

pool-reboot

Answer

pool-pause

Question 7

Which THREE of the following are valid elements inside the <interface type='bridge'> block?

Accepted Answer

. Option A is correct because is the required child element that tells libvirt which host bridge the guest interface should be attached to, and it is valid inside . Option D is correct because is a valid child element that selects the emulated NIC model presented to the guest, with virtio being the paravirtualized option. Option E is correct because is a valid child element used to assign a specific MAC address to the guest interface. Options B and C are not valid here: and are not children of ; IP/gateway configuration belongs in the guest OS or in higher-level network definitions, not in the interface's bridge block.

Answer

Answer

Question 8

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 9

Which THREE of the following XML elements are used to define a virtual disk in a domain?

Accepted Answer

. In libvirt domain XML, a virtual disk is defined inside a element, and the three marked options are its core components. Option A, , specifies the hypervisor driver (qemu) and the disk image format (qcow2), which tells libvirt how to handle the backing file. Option D, , defines the guest-visible device name and the bus/controller (virtio) used to attach the disk to the VM. Option E, , points to the host-side disk image file that backs the virtual disk. The unmarked options do not belong: and are used in filesystem/container or guest-agent contexts (e.g., devices for virtio-9p or virtiofs), not for defining a standard virtual disk in a domain.

Answer

<mount-point path='/'>

Answer

Question 10

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 11

You are managing a Xen host and need to live-migrate a domain between two physical servers. The migration fails with a domain lock error. Which command is the standard way to initiate a live migration while ensuring the target host is prepared to receive the domain?

Accepted Answer

xl migrate . The xl migrate command is the standard Xen tool for live-migrating a domain to another host, and it handles the necessary preparation on the target host (such as creating the domain configuration and transferring memory state) to receive the domain. It is the direct counterpart to xm migrate in the newer xl toolstack.

Answer

xl save && xl restore

Answer

xen-migrate --live

Answer

virsh migrate --live

Question 12

A libvirt storage pool of type 'dir' contains several qcow2 images. You want to create a new snapshot of an existing VM using virsh. Which command sequence is required to create an internal snapshot of the VM's current state?

Accepted Answer

virsh snapshot-create-as --domain . The command 'virsh snapshot-create-as --domain ' creates an internal snapshot of the VM, capturing the state of all its disks and optionally memory. This is the default behavior for virsh snapshot-create-as when no '--disk-only' or '--memspec' is specified, and it requires the disk format to support snapshots (e.g., qcow2).

Answer

virsh snapshot-create-as --domain --disk-only

Answer

qemu-img snapshot -c

Answer

virsh domblklist <vm> --snapshot

Question 13

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 14

You are troubleshooting a libvirt migration that fails with 'Operation not supported: Migration requires a storage pool'. You need to perform a block migration where the storage is copied to the destination host. Which command-line flag enables this functionality?

Accepted Answer

--copy-storage-all. The --copy-storage-all flag tells libvirt to copy all disk images from the source host to the destination during migration, enabling block migration when shared storage is not available. This directly addresses the 'Migration requires a storage pool' error by supplying the missing storage transfer behavior.

Answer

--live-disk

Answer

--migrate-storage

Answer

--block-migrate

Question 15

You have a qcow2 disk image that is growing too large. You want to shrink the file size on the host while keeping the virtual disk the same size. Which steps must you perform first?

Accepted Answer

Run fstrim in the guest, then use qemu-img convert -O qcow2.. To shrink a qcow2 file on the host while keeping the virtual disk size unchanged, you must first reclaim unused blocks inside the guest by running fstrim (which issues TRIM/discard to the virtual disk), then compact the image with qemu-img convert -O qcow2, which rewrites only allocated clusters into a new sparse file. This two-step process is the standard method for reducing qcow2 on-disk footprint without altering the guest's visible disk capacity.

Answer

Delete files in the guest and use qemu-img resize.

Answer

Use virsh blockpull.

Answer

Use qemu-img check -r all.

Answer

Run dd if=/dev/zero to fill the disk.