305-300 Practice Test 7 — 10 Questions

Question 1

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?

Choose an answer to begin — your selection is scored in the full session.

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 2

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 3

A cloud-init configuration file is failing to apply the 'write_files' module. Which log file on the target instance should you examine to diagnose the parsing error?

Accepted Answer

/var/log/cloud-init.log. The /var/log/cloud-init.log file is the primary log for cloud-init and records all stages of the cloud-init process, including the parsing and execution of modules like write_files. When a configuration file fails to apply, cloud-init logs detailed error messages, such as syntax errors or invalid YAML, in this file. Therefore, examining /var/log/cloud-init.log is the correct way to diagnose parsing errors.

Answer

/var/log/syslog

Answer

/var/log/messages

Answer

/var/log/auth.log

Question 4

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 5

Which option for 'qemu-img create' allows you to create a preallocated image?

Accepted Answer

-o preallocation=full. The correct syntax is qemu-img create -f qcow2 -o preallocation=full disk.qcow2, where preallocation is a format-specific option passed via -o. Setting preallocation=full allocates all the space on the host immediately, avoiding fragmentation and improving write performance at the cost of disk usage. Other valid values are off, metadata, and falloc.

Answer

--prealloc=true

Answer

-p full

Answer

-f preallocated

Question 6

You want to limit the bandwidth of a virtual network interface. Which XML element within <interface> allows you to configure this?

Accepted Answer

. The element inside is the libvirt XML mechanism for traffic shaping on a virtual NIC. It contains and child elements, each accepting an 'average' attribute in kilobytes per second, which sets the token-bucket rate limit enforced by the host's traffic control subsystem.

Answer

<limit-rate>1000</limit-rate>

Answer

<network-speed>1000</network-speed>

Answer

<traffic-control>1000</traffic-control>

Question 7

What is a 'snapshot' in virtualization?

Accepted Answer

A saved state of a virtual machine at a point in time. A snapshot in virtualization is a saved state of a virtual machine at a specific point in time, capturing disk contents (and optionally memory/CPU state) so the VM can be reverted to that state. It is not a hardware config, log, or full host backup. Snapshots enable rollback after changes or failures.

Answer

A virtual hardware configuration

Answer

A log file of guest activity

Answer

A backup of the entire host system

Question 8

You are building a multi-stage Dockerfile and want to copy a binary from the 'builder' stage to the final stage. Which syntax is correct?

Accepted Answer

COPY --from=builder /bin/app /bin/app. Docker's multi-stage build feature allows COPY --from=<stage> to pull artifacts from a previously built stage (or an external image) into the current stage. The syntax COPY --from=builder /bin/app /bin/app copies the binary /bin/app from the stage named 'builder' into the final image at /bin/app, keeping the final image small by excluding the builder's toolchain and dependencies.

Answer

ADD --from=builder /bin/app /bin/app

Answer

COPY builder:/bin/app /bin/app

Answer

COPY --stage=builder /bin/app /bin/app

Question 9

Which TWO of the following commands can be used to manage virtual networks in libvirt?

Accepted Answer

virsh net-define. Option A, virsh net-define, is correct because it defines a persistent virtual network in libvirt from an XML configuration file, creating the network object that can later be started and made autostart. Option E, virsh net-list, is correct because it lists the virtual networks known to libvirt and can show their state (active/inactive) and autostart flag, making it a core management command. Option B, virsh net-config, does not exist as a libvirt subcommand; network XML is edited via virsh net-edit or net-define. Option C, virsh net-start-all, is not a valid virsh command; individual networks are started with virsh net-start, and autostart is set with virsh net-autostart. Option D, virsh net-status, is not a real libvirt subcommand; network state is obtained through virsh net-list or virsh net-info.

Answer

virsh net-config

Answer

virsh net-start-all

Answer

virsh net-status

Question 10

You are migrating a legacy application to an LXC container and need to ensure the container has access to the host's /dev/sda block device. Which configuration key must be added to the container's configuration file?

Accepted Answer

lxc.cgroup.devices.allow = b 8:0 rwm. LXC controls device access through the cgroup devices controller, and the config key lxc.cgroup.devices.allow uses the syntax 'TYPE MAJOR:MINOR PERMISSIONS'. For /dev/sda, the type is 'b' (block), major 8, minor 0, and permissions 'rwm' (read, write, mknod). This whitelists the block device so the container can access it, and it must be paired with a bind mount (lxc.mount.entry) to actually expose the device node inside the container.

Answer

lxc.mount.device = /dev/sda

Answer

lxc.cap.sys_admin = 1

Answer

lxc.dev.access = /dev/sda