305-300 Exam Dumps - LPIC-3: Virtualization and Containerization - Exam 305, version 3.0

The type attribute of a element in a libvirt domain definition specifies the hypervisor used for running the domain. The allowed values are driver specific, but include “xen”, “kvm”, “hvf” (since 8.1.0 and QEMU 2.12), “qemu” and "lxc"1. Therefore, the valid values among the options are C. kvm and E. lxc. KVM stands for Kernel-based Virtual Machine, which is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V)2. LXC stands for Linux Containers, which is an operating system-level virtualization method for running multiple isolated Linux systems (containers) on a single control host3. The other options are not valid values for the type attribute, asthey are either not hypervisors or not supported by libvirt. References:http://libvirt.org/formatdomain.html

https://libvirt.org/formatcaps.html

Docker stack is a command that allows users to deploy and manage a stack of services on a Docker Swarm cluster. A stack is a group of interrelated services that share dependencies and can be orchestrated and scaled together. A stack is typically defined by a Compose file, which is a YAML file that describes the services, networks, volumes, and other resources of the stack. To use docker stack to run a Compose file on a Swarm, the user must first create and initialize a Swarm cluster, which is a group of machines (nodes) that are running the Docker Engine and are joined into a single entity. The Swarm cluster has one or more managers, which are responsible for maintaining the cluster state and orchestrating the services, and one or more workers, which are the nodes that run the services.

When the user runs docker stack deploy with a Compose file, the command parses the file and creates the services as specified. However, docker stack does not build or upload the images referenced in the Compose file to any registry. Instead, it instructs the Swarm nodes to pull the images from a registry, which can be the public Docker Hub or a private registry. The user must ensure that the images are available in the registry before deploying the stack, otherwise the deployment will fail. The user can use docker build and docker push commands to create and upload the images to the registry, or use an automated build service such as Docker Hub or GitHub Actions. The user must also make sure that the image names and tags in the Compose file match the ones in the registry, and that the Swarm nodes have access to the registry if it is private. By pulling the images from a registry, docker stack ensures that the Swarm nodes have the same and latest version of the images, and that the images are distributed across the cluster in an efficient way.

The other options are not correct. Docker stack does not build the images locally or on the Swarm nodes, nor does it copy or transfer the images to the Swarm nodes. Dockerstack also does not pass the images to the Swarm master, as this would create a bottleneck and a single point of failure. Docker stack relies on the registry as the source of truth for the images, and delegates the image pulling to the Swarm nodes. References:

Deploy a stack to a swarm | Docker Docs1

docker stack deploy | Docker Docs2

docker build | Docker Docs3

docker push | Docker Docs4

The ENTRYPOINT instruction in a Dockerfile specifies the default command to run when a container is started from the image. The ENTRYPOINT instruction can be written in two forms: exec form and shell form. The exec form uses a JSON array to specify the command and its arguments, such as [ “executable”, “param1”, “param2” ]. The shell form uses a single string to specify the command and its arguments, such as “executable param1 param2”. The shell form is converted to the exec form by adding /bin/sh -c to the beginning of the command. Therefore, the following statements in a Dockerfile are equivalent and will lead to a container that outputs hello world:

ENTRYPOINT [ “echo hello world” ] ENTRYPOINT [ “/bin/sh”, “-c”, “echo hello world” ] ENTRYPOINT “echo hello world” ENTRYPOINT [ “echo”, “hello”, “world” ] ENTRYPOINT [ “/bin/sh”, “-c”, “echo”, “hello”, “world” ] ENTRYPOINT “echo hello world”

The other statements in the question are invalid or incorrect. The statement A. ENTRYPOINT “echo Hello World” is invalid because it uses double quotes to enclose the entire command, which is not allowed in the shell form. The statement D. ENTRYPOINT echo Hello World is incorrect because it does not use quotes to enclose the command, which is required in the shell form. The statement E. ENTRYPOINT “echo”, “Hello”, “World” is invalid because it uses double quotes to separate the command and its arguments, which is not allowed in the exec form. References:

Dockerfile reference | Docker Docs

Using the Dockerfile ENTRYPOINT and CMD Instructions - ATA Learning

Difference Between run, cmd and entrypoint in a Dockerfile

The default path to the Docker daemon configuration file on Linux is /etc/docker/daemon.json. This file is a JSON file that contains the settings and options for the Docker daemon, which is the service that runs on the host operating system and manages the containers, images, networks, and other Docker resources. The /etc/docker/daemon.json file does not exist by default, but it can be created by the user to customize the Docker daemon behavior. The file can also be specified by using the --config-file flag when starting the Docker daemon. The file must be a valid JSON object and follow the syntax and structure of the dockerd reference docs12. References:

Docker daemon configuration file - Medium3

Docker daemon configuration overview | Docker Docs4

docker daemon | Docker Docs5

LXD supports the following network interface types in an LXD container configuration1:

macvlan: Creates a virtual interface on the host with a unique MAC address and attaches it to an existing physical interface. This allows the container to have direct access to the physical network, but prevents communication with the host and other containers on the same host2.

bridged: Connects the container to an existing bridge interface on the host. This allows the container to communicate with the host and other containers on the same bridge, as well as the external network if the bridge is connected to a physical interface3.

physical: Passes an existing physical interface on the host to the container. This allows the container to have exclusive access to the physical network, but removes the interface from the host4.

The other network interface types, ipsec and wifi, are not valid in an LXD container configuration. Ipsec is a protocol for secure communication over IP networks, not a network interface type. Wifi is a wireless technology for connecting devices to a network, not a network interface type. References:

About networking - Canonical LXD documentation

Macvlan network - Canonical LXD documentation

Bridge network - Canonical LXD documentation

Physical network - Canonical LXD documentation