305-300 Practice Exam 2 — 20 Questions

Question 1

Which command is used to stop all running containers?

Accepted Answer

docker stop $(docker ps -q). 'docker stop $(docker ps -q)' pipes the IDs of running containers to the stop command.

Answer

docker kill --all

Answer

docker rm -f *

Answer

docker prune

Question 2

What does the 'docker rm' command do?

Accepted Answer

Removes a container. 'docker rm' deletes one or more stopped containers.

Answer

Renames a container

Answer

Stops a container

Answer

Removes an image

Question 3

You are performing a live migration of a VM using libvirt. The source and destination hosts share a common storage pool (NFS). Which option should be used with 'virsh migrate' to ensure only the memory state is transferred?

Accepted Answer

--copy-storage-none. --live --copy-storage-none allows migration without moving the disk image if the storage is shared.

Answer

--shared-storage

Answer

--migrate-memory-only

Answer

--unsafe

Question 4

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 and elements are used for CPU pinning.

Answer

Answer

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

Answer

Question 5

In systemd-nspawn, how can you execute a command inside a container that is already running?

Accepted Answer

machinectl shell. 'machinectl shell' is the command used to spawn a shell inside a running container.

Answer

systemctl start

Answer

systemd-nspawn -run

Answer

nsenter

Question 6

Which command-line option is used to run a Docker container in the background (detached mode)?

Accepted Answer

-d. The -d flag specifies that the container should run in the background.

Answer

-i

Answer

--bg

Answer

-b

Answer

-t

Question 7

Which hypervisor type is considered 'Type 1' virtualization?

Accepted Answer

Xen. Type 1 hypervisors (bare metal) run directly on the hardware, such as Xen.

Answer

VMware Workstation

Answer

VirtualBox

Answer

QEMU (user mode)

Question 8

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. Multi-stage builds, minimizing layers, and cleaning up caches are standard practices.

Answer

Use the FROM latest tag for all base images

Answer

Always install recommended packages for security

Question 9

In an OpenVZ environment, you need to limit the number of processes a container can create. Which parameter in the container configuration file should be modified?

Accepted Answer

NUMPROC. The 'nproc' (or numproc) parameter in the OpenVZ configuration limits the total number of processes a container is allowed to hold.

Answer

PHYSPAGES

Answer

KMEMSIZE

Answer

PRIVVMPAGES

Question 10

You are troubleshooting a problem where an LXC container cannot access its own /dev/null. What is a common cause in a non-root container?

Accepted Answer

Missing mknod permission. Lack of device node creation in the container's /dev directory or improper cgroup permissions often causes this.

Answer

Wrong kernel version

Answer

Host kernel panic

Answer

Insufficient RAM

Question 11

Which THREE storage drivers are supported by Docker?

Accepted Answer

devicemapper. Overlay2, devicemapper, and aufs are well-known Docker storage drivers.

Answer

xfs

Answer

ext4

Question 12

You are running a Docker container and need to map port 8080 on the host to port 80 in the container. Which command argument should you use?

Accepted Answer

-p 8080:80. The -p flag (or --publish) defines port mapping.

Answer

-p 80:8080

Answer

--port 8080:80

Answer

--map 8080:80

Question 13

When building a Dockerfile, which instruction should be used to define the user context for subsequent RUN, CMD, and ENTRYPOINT instructions?

Accepted Answer

USER. The USER instruction sets the UID/GID for processes executed in subsequent steps.

Answer

WORKDIR

Answer

RUN useradd

Answer

AS

Question 14

You are using systemd-nspawn. How do you create an image of a container to be used as a template?

Accepted Answer

machinectl export-tar. 'machinectl export-tar' is used to export a systemd-nspawn container (machine) to a tarball.

Answer

tar -cvf

Answer

docker export

Answer

lxc-copy

Question 15

Which TWO commands are valid for inspecting container network settings?

Accepted Answer

docker inspect. 'docker inspect' provides detailed JSON, and 'docker network inspect' shows network-specific details.

Answer

docker show net

Answer

docker net status

Answer

docker list network

Question 16

In the context of container orchestration, what is the role of a 'sidecar' container?

Accepted Answer

To provide auxiliary services like logging or monitoring for the main container. A sidecar container runs alongside the main application container within the same pod to extend or enhance its functionality.

Answer

To act as a load balancer for the cluster

Answer

To store persistent data for the primary container

Answer

To run in a separate network namespace

Answer

To replace the main container when it crashes

Question 17

Which THREE instructions in a Dockerfile can modify the image's filesystem?

Accepted Answer

ADD. RUN, COPY, and ADD all add or modify content within the image layers.

Answer

ENV

Answer

EXPOSE

Question 18

When migrating a Libvirt domain using 'virsh migrate --live', which option must be specified to ensure the guest's memory state is copied over the network?

Accepted Answer

--copy-storage-all. The --live option manages the memory transfer, but the --copy-storage-all or --block-incremental option is required if the disks are not on shared storage.

Answer

--shared-storage

Answer

--migrate-disk

Answer

--memory-copy

Question 19

You need to inspect the metadata of a specific Docker image without pulling it from a remote registry. Which command should you use?

Accepted Answer

docker manifest inspect. docker manifest inspect allows retrieving information about an image's manifest without downloading the layers.

Answer

docker pull --metadata

Answer

docker image history

Answer

docker image inspect

Question 20

Which command shows the history of layers in a Docker image?

Accepted Answer

docker history. 'docker image history' displays the layers and the commands that created them.

Answer

docker log

Answer

docker layers

Answer

docker image info