305-300 Practice Test 3 — 10 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